 |
|
|
|
|
 |
||||
|
|
|
|
|
| CME credit for this activity has expired. |
|
Scientific Basis for Excisional Biopsy of Skin Tumors Released: October 2005 Sponsored by Dannemiller Memorial Educational Foundation  Supported by an unrestricted educational grant from 
Faculty: Kant Y. Lin, M.D. Professor of Plastic Surgery Chief of Division of Craniofacial Surgery University of Virginia Health Systems Charlottesville, Virginia William B. Long III, M.D. President and Medical Director Legacy Verified Level I Shock Trauma Center for Children and Adults Portland, OR Richard F. Edlich, M.D., Ph.D. Distinguished Professor Emeritus of Plastic Surgery Biomedical Engineering, and Emergency Medicine Founder of the DeCamp Burn and Wound Healing Center University of Virginia Health Systems Director of Trauma,Prevention, Education and Research Trauma Specialists, LLP, Legacy Verified Level I Shock Trauma Center for Pediatrics and Adults Legacy Emanuel Hospital, Portland, OR Statement of Need: Continuing research into present and future techniques of the scientific basis for excisional biopsy of skin tumors is important for all surgeons and surgical specialists. Skin neoplasms vary from those that are benign to others that are highly malignant. They are so common that every person will develop at least one or more skin tumors. More than 600,000 new cases of malignant skin tumors are diagnosed each year. Goal: The broad mission of this continuing education program is to teach the surgeon and surgical specialists the scientific basis for excisional biopsy of skin tumors. I. Objectives: At the completion of this activity, the participant should be able to:
To receive credit, participants should, in order, view the objectives, read the educational material, then go to the link at the end of this activity to complete the post-test, evaluation, and then print the CME certificate. This activity should take approximately 1 hour to complete. This activity is available through October 31, 2008. No credit will be awarded after this date. Target Audience: This educational program is intended for general surgeons as well as other surgical specialists or physicians involved in wound closure. Accreditation: The Dannemiller Memorial Educational Foundation is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians. The Dannemiller Memorial Educational Foundation designates this educational activity for a maximum of 1.0 AMA PRA Category 1 Credit(s),TM. Physicians should only claim credit commensurate with the extent of their participation in the activity. The Dannemiller Memorial Educational Foundation is an approved provider of the California Board of Registered Nursing. Provider approved by the California Board of Registered Nursing, Provider Number 4229 for 1.2 contact hours. RNs outside California must verify with their licensing agency for approval of this course. Faculty Disclosure: Kant Y. Lin, M.D. in accordance with ACCME requirements Dr. Lin has nothing to disclose. William B. Long III, M.D. in accordance with ACCME requirements Dr. Long has nothing to disclose. Richard F. Edlich, M.D., Ph.D. in accordance with ACCME requirements Dr. Edlich has nothing to disclose. Sponsor's Disclosure: In accordance with the Accreditation Council for Continuing Medical Education (ACCME), the Dannemiller Memorial Educational Foundation requires that any person who is in a position to control the content of a CME activity must disclose all relevant financial relationships they have with a commercial interest. Accordingly: The Dannemiller Memorial Educational Foundation staff that was involved in the development of this activity has no financial relationships with any commercial interests that are relevant to this activity. Disclaimer The content and views presented in this educational activity are those of the authors and do not necessarily reflect those of the Dannemiller Memorial Educational Foundation or US Surgical/Division of Tyco Healthcare. This material is prepared based upon a review of multiple sources of information, but it is not exhaustive of the subject matter. Therefore, healthcare professionals and other individuals should review and consider other publications and materials on the subject matter before relying solely upon the information contained within this educational activity. INTRODUCTION Skin neoplasms vary from those that are benign to others that are highly malignant. They are so common that every person will develop at least one or more skin tumors. More than 600,000 new cases of malignant skin tumors are diagnosed in the United States each year.1 Basal cell carcinoma (BCC) accounts for 65% to 80% of the cases. Squamous cell cancer (SCC) is the second most common malignant skin tumor and comprises 10% to 20% of the cases. Approximately 32,000 new cases of melanoma are diagnosed annually in the United States. At the current rate, 1 of every 105 Americans will develop melanoma. EXCISIONAL BIOPSY TECHNIQUE The treatment of skin tumors is based on either their complete removal or destruction. One standard method of treatment is excisional biopsy. Because the definitive diagnosis of the skin tumor (especially precancerous ones) depends on histopathologic examination complemented by clinical data, the surgeon must provide the pathologist with as much clinical data as possible. This report will describe a systematic approach to the excisional biopsy of skin tumors, which is so well designed that it allows any physician to remove the tumor completely and achieve the most aesthetically pleasing results. This technique is designed to excise a circular specimen of skin and underlying adipose tissue, with a diameter of 12 mm or less, after which the defect is closed primarily. This excisional biopsy technique is ideally suited for most skin tumors, including benign lesions and small superficial BCC or SCC. There are seven technical considerations involved in the excisional biopsy of skin tumors: (1) aseptic technique, (2) examination and demarcation of skin lesion, (3) skin biomechanical properties, (4) anesthesia, (5) excisional biopsy, (6) wound closure, and (7) postoperative care.2 Aseptic Technique The physician must use aseptic technique and wear a cap, mask, and powder-free gloves. Powder-free gloves are recommended because the glove powders (e.g., cornstarch) are foreign bodies that damage the host's resistance to infection.3 We recommend powder-free gloves coated with an acrylate polymer. The polymer facilitates donning of the gloves with either dry or wet hands. The acrylate lining provides a barrier between the skin and the latex, which is especially important to individuals with sensitivities to latex proteins or accelerators. If the patient or the physician has evidence of latex sensitivity, we recommend that the physician wear the Biogel® SkinsenseTM N Universal non-latex powder-free glove.4 Hair is a source of wound contamination, and removal of hair prevents it from becoming entangled in suture and the wound during closure. (Fig. 1) However, the infection rate in surgical wounds following razor preparation of the skin is significantly greater than that after hair removal by electric clippers.5 The increased incidence of infection following razor preparation is probably related to the trauma inflicted by the razor. As a result of the shave, wounded hair follicles provide access to and substrate for bacteria. Because surgical electric clippers cut hair close to the skin surface without nicking the skin, we now use only electric clippers to remove hair. Recent advances in the design of electric clippers have eliminated sharp edges that can abrade the skin. A new surgical clipper has a disposable clipper blade assembly that does not require cleaning, assembly, or disassembly. (Fig. 2)5 After hair removal, the skin is then cleansed with a fine, pore-cell-sized sponge soaked in poloxamer 188. This nontoxic surfactant is an excellent skin-wound cleanser that can be safely poured into the patient's eye.6 Examination and Demarcation of Skin Lesion The physician's visualization of the wound can be enhanced by magnification (2.5X) loupes. Physicians uniformly prefer keplerian loupes over the Galilean lens system. The advantages of the keplerian lens system are its increased field of view and clearer peripheral view.7 This system allows the physician to visualize the exquisite details of the skin tumor and to perform wound closure using meticulous surgical technique. Basal cell carcinoma (BCC) occurs usually in sun-exposed skin sites and is seen as pearly papules, frequently containing prominent, dilated subepidermal blood vessels (telangiectasias). Some lesions contain melanin pigment. Despite the low potential for metastasis, advanced lesions have the capability of local invasion with ulceration and subsequent destruction of underlying bone.8 BCC frequently extends beyond its visible borders. For tumors with a diameter of less than 2 cm, a minimum margin of 4 mm is necessary to remove completely the tumor in more than 95% of the cases. Sclerosis or morpheaform variants of this tumor require more than a 7 mm margin from clinical evident tumor.9 Squamous cell cancer is also found in sun-exposed skin sites. Although these tumors usually remain locally confined, they exhibit a low, but significant, propensity to metastasize. When this tumor does not advance through the basement membrane of the dermatoepidermal juncture (in situ carcinoma), it appears macroscopically as a sharply defined, red scaling plaque. Advanced invasive lesions are nodular with a variable amount of keratin production (hyperkeratosis) and ulceration. Four-millimeter margins are adequate for removal of most SCC. However, certain tumor characteristics are associated with a greater risk of tumor invasion and include size of 2 cm or larger, invasion of the subcutaneous tissue, location in high-risk areas (e.g., scalp, ears, eyelids, nose, lips), and high histologic grades (2, 3, 4).10 The clinical characteristics of early melanoma are remarkably similar, regardless of the anatomic site. It is important that physicians recognize four characteristic features of these tumors. First, the shape of early malignant melanoma is often asymmetric, unlike benign pigmented lesions whose shapes are generally round and symmetric. (Fig. 3) Second, the borders of early malignant melanoma are often irregular, whereas benign pigmented lesions tend to have regular margins. Third, macular malignant melanomas are usually variegated, ranging from hues of tan and brown to black, sometimes intermingled with red and white; benign pigmented lesions are more uniform in color. Fourth, the diameter of malignant melanoma is frequently 6 mm or larger, whereas most benign pigmented lesions generally have diameters of less than 6 mm.11 Until 1977, a 3 to 5 cm skin margin of normal skin in all directions from the visible borders of the primary melanoma was considered to be optimal for removal of all cutaneous melanomas.11 This dictum was questioned when no adverse effects were reported in a small series of melanomas not thicker than 0.76 mm that underwent limited excision, in some instances, of 2 mm of normal skin. The absence of local recurrence in a group of patients with primary melanomas thinner than 1 mm and the very low rate of recurrence for thicker melanomas (>1 mm) indicate that a narrow 1 cm margin excision is a safe and effective procedure.12 Narrow excision of malignant melanoma must be performed as follows: the skin must be cut 1 cm from the visible margins of the primary melanoma and the excision must be 1 or 2 cm wider in subcutaneous fat, extending through to muscular fascia.13 Consequently, the physician's plan for excisional biopsy is dictated by the suspected pathology of the skin lesion. A margin of excision must be identified that allows the lesion to be completely excised. Once the wound margins have been defined and skin defect created after excision of the tumor, the configuration of the resulting defect is determined.14 Skin Biomechanical Properties The ultimate appearance and function of a scar after closure of excisional biopsy can be predicted by the static and dynamic skin tensions on the surrounding skin. The static skin tensions are the underlying bony framework when the body remains motionless. These inherent forces are dependent partly on the natural characteristics of dermal collagen fibers and partially on the pattern in which they are woven. Clinical evidence of these tensions is the retraction of the edges of the wounds, permitting visualization of the underlying tissue.14 Static skin forces differ considerably in their magnitude and direction within the same person and between individuals. Large differences are noted between various anatomic sites. The skin in one region may be relatively taut; in others, it is lax. In one human volunteer, the static skin tensions were fivefold greater in his extremities than in his abdominal skin.14 In some regions of the body, there is a directional orientation of static skin tensions. This was first appreciated by Dupuytren15 in 1834 when he examined a suicide victim who sustained three self-inflicted puncture wounds made by an awl. He noted that the wounds assumed an elliptical shape similar to the shape of skin wounds caused by a knife. He concluded that skin tensions in the long axis of the defect were substantially greater than in its short axis, distorting the wound accordingly. In 1861, Langer published a more comprehensive study on the biomechanical properties of human skin.16 His observations were made on the skin of cadavers, which were lying in the normal anatomic position, by inserting an awl 2.0 mm in diameter to a depth of 2.5 mm. As Dupuytren reported, the circular defect was drawn into an ellipse. By drawing lines between the major axes of the ellipses, Langer identified the direction in which the tension predominated. These static lines of maximal skin tensions are known as "Langer's lines." In 1892, Kocher17 advocated that surgical incisions should follow Langer's lines. For nearly 100 years, surgeons referred to Langer's lines as the most appropriate guides for incisions that would heal with minimal scarring. It is currently realized that the charts of Langer's lines appearing in textbooks are articles having little practical application because they are erroneous in most cases and do not consider the highly important effect of the dynamic skin tensions on the healing scar.18 The static skin tensions continually pull on the wound edges, resulting in the development of a visible scar. The width of this scar is proportional to the magnitude of skin tensions.18 Excisions made in skin subjected to strong skin tensions usually heal with wide, unattractive scars. In contrast, narrow, fine scars often result from the repair of excisions made in skin with weak static skin tensions. Dynamic skin tensions also have considerable impact on the magnitude and extent of scar formation. These changing tensions are caused by a combination of forces that are associated with either joint movement of mimetic muscle contraction.18 In the face, the dynamic skin tensions are perpendicular to natural skin wrinkles and parallel to the direction of contraction of the underlying mimetic muscles. Similarly, the dynamic skin tensions are perpendicular to the transverse axis of the joint. The clinical significance of dynamic tensions is apparent in skin of changing dimensions where elasticity is needed for normal function. In general, a linear scar intersecting the wrinkle lines, transverse axis of a joint, or lying parallel to the dynamic skin tensions can result in a serious contracture because the scar does not stretch or recoil like uninjured skin. Anesthesia Infiltration anesthesia is preferred over regional nerve block because it does not interfere with muscle movement that causes dynamic tensions, which elongate the configuration of the defect. Regional nerve block affects the nerve supply to the muscles that account for dynamic skin tensions and prevents evaluation of the effect of muscle contraction on the distortion of defect resulting from excisional biopsy. Infiltration anesthesia is accomplished with a 1-inch long 30-gauge needle attached to a 5-mL syringe. Because the amide type local anesthetic agents appear to be relatively free of causing sensitivity and allergic reactions characteristic of the ester type derivative, physicians usually use amide type agents (e.g., lidocaine, bupivacaine) for infiltration anesthesia.19 These anesthetic agents do not damage issue defenses or potentiate infection. In addition, the pain of subdermal injection, the onset of anesthesia, and the frequency of satisfactory anesthesia are similar. The pain of administration of local anesthetics can be reduced dramatically by pH buffering of the local anesthetic agents before injection. However, this is not recommended for bupivacaine because precipitate forms. Because the duration of local anesthesia induced by bupivacaine is nearly four times longer than that by lidocaine, bupivacaine may be preferred for infiltration anesthesia. The duration of the anesthetic activity of these agents can be further enhanced by the addition of the vasoconstrictor epinephrine, which slows the clearance of the anesthetic agent from the tissue (0.5% bupivacaine with 1:200,000 epinephrine). An understanding of the directional orientation of the dynamic skin tensions at the biopsy site provides insight into the sites of needle placement for infiltration anesthesia. After the patient contracts the muscles of facial expression or flexes the joint, the physician can visualize the outlined circular biopsy site change its shape from a circle to an ellipse. At a site approximately 1 cm from the midportion of the end of the ellipse, the point of the bevel of the needle is passed through the skin into the subcutaneous tissue. The point of the needle lying in the subcutaneous tissue is first directed to one side of the elliptically shaped biopsy site. Before injecting the local anesthetic agent, the syringe barrel is withdrawn to aspirate blood if the needle is positioned in a vessel. Aspiration of blood is a forewarning of the danger of intravascular injection, which can be avoided by repositioning the needle in another site in the subcutaneous tissue. When syringe aspiration is accomplished without visualization of blood, the needle is slowly (≥10 seconds) withdrawn as approximately 1.5 mL of the local anesthetic agent is injected into tissue. As the needle nears its entry position, the direction of the needle is changed so that it can be positioned on the contralateral side of the wound, after which the technique for introducing the local anesthetic agent is repeated. Five to six minutes after injecting the anesthetic agent, the needle is reintroduced in the anesthetized skin that borders one lateral edge of the excisional biopsy site after it is advanced to a site opposite the original injection site. The technique for introducing the anesthetic agent is then repeated. Through anesthetized skin bordering the contralateral side of the biopsy site, the needle is passed and advanced toward the site previously described. After waiting 5 to 6 more minutes, the circular excisional biopsy can be started in the anesthetized site. The depth and speed of the injection are important determinants of the magnitude of discomfort experienced by the patient. Placement of the needle into the superficial dermis is more uncomfortable than needle passage into the subdermal area. Moreover, intradermal injections resulting in superficial wheals are significantly more painful than injections into the subdermal region and cause distortion of the skin. Rapid injection (<2 seconds) of a local anesthetic agent always causes more pain than when the same volume of anesthetic agent is instilled over 10 seconds. Intracutaneous installation of lidocaine at 37° C (98.6° F) is no less painful than injection at 21° C (69.8° F). Full anesthesia to pinprick is produced immediately with intradermal injections and is present 5 to 6 min. after subdermal injection. A reliable method of minimizing the discomfort of infiltration anesthesia is to use a syringe fitted with a number 30 needle and to inject the smallest amount of anesthetic agent slowly (≥10 seconds) into the deep dermal subcutaneous tissue as the needle is slowly withdrawn. A new alternative to the use of infiltration anesthesia for excisional skin biopsies is the topical anesthesia containing a eutectic mixture of lidocaine and prilocaine in a water emulsion cream base.20 The emulsion is applied to the tumor site, which is covered by an occlusive dressing. It can take up to 1 hour before the anesthesia is complete. A slight blanching of the skin in the areas that have been in contact with the cream is noticed in most cases. This effect is a useful marker for complete anesthesia, which persists for 1 to 2 hours. Excisional Biopsy Most skin lesions are amenable to a circular excision. In these instances, it is worthwhile to use circular-shaped excisions. Circular excisional biopsy had its beginning less than a century ago when a new use for the ancient trephine was discovered.21 Small (≤4 mm) cutaneous reusable metal trephines or punches with sharp edges were used. The metal trephines were placed on the surface of the skin and then rotated, cutting out a circular piece of skin corresponding to the internal diameter of the lumen of the trephine. This technique of excision biopsy has several advantages over scalpel incision. The circular biopsy of the skin can be performed considerably faster using trephines than using scalpel excisions. More importantly, the trephine biopsy of the skin results in a circular defect whose shape is changed by the predominant local static and dynamic tensions. The defect elongates in the direction of maximal skin tension, revealing the long axis of the defect. Closure of the elliptically shaped defect in the direction of its long axis results in a narrow scar.    The reusable metal trephines have been replaced by disposable trephines that have ribbed plastic handles attached to 316 stainless steel circular cutting blades. (Fig. 4) Because disposable trephines have been used predominantly for incisional biopsies, diameters of the circular cutting blades have been relatively small (≤4 mm). Use of disposable trephines for excision biopsy has been limited by the small size because they frequently do not provide adequate margins of uninvolved tissue surrounding the skin lesion. Consequently, disposable trephines 22 with wider diameter circular cutting blades, up to 12 mm, have been specially developed for excisional biopsy. The height of the cutting blades is 6 mm to provide adequate and controlled depth of the specimen taken at excisional biopsy. Our extensive clinical experience with these disposable large skin trephines (more than 500 patients) has resulted in a reliable surgical technique that can be replicated in both the office and the medical center. A disposable trephine whose diameter corresponds to that of the outline of the margins of the skin tumor is selected. If the margins do not have a circular configuration, the margins of the skin are incised by a number 15 stainless steel scalpel. The plastic handle of the disposable dermatome is held between the thumb and the index finger. (Fig. 4)  The skin lesion should be in the central portion of the circular specimen taken at biopsy. The site of the excisional biopsy can be predicted by first positioning and then pressing the appropriate trephine against the skin, which results in a temporary indentation of the skin. (Fig. 5)  Once the lesion is appropriately centered in the circular biopsy site, the trephine is rotated back and forth between the fingers, cutting the circular specimen depth, which is 6 mm. (Fig. 6)   The trephine is then removed from the biopsy site. (Fig. 8)  When the circular biopsy site is separate from the surrounding skin, the biopsy site maintains its circular configuration, but reduces considerably in size. Using a fine tip mosquito pick-ups, the surgeon grasps one edge of the biopsy site, which is elevated from the surrounding intact skin. With the mosquito pick-ups elevating the excised biopsy specimen, the cut edges of the underlying adipose tissue that have a tubular shape are very apparent. The base of this long tubular length of adipose tissue is transected with Metzenbaum scissors. (Fig. 9)  After excision of the skin tumor, note how the static skin attachments have elongated the wound so that it now assumes a stellate shaped defect. (Fig. 10)  In our experience, the direction of the long axis of the elliptical defect often does not coincide with either Langer's lines or relaxed skin tension lines, indicating that these lines frequently do not accurately predict the orientation of the resulting defect. Consequently, preplanning the orientation of the lenticular shaped excision with length to width ratio of 4:1 has several disadvantages. The direction of the wound closure may be less than ideal. In addition, the length of the closed wound after excisional biopsy is unnecessarily long because it does not account for the elliptical wound deformation. Each biopsy specimen is fixed separately in a bottle containing 10% formalin solution and is sent for histopathologic examination. Most bleeding can be controlled by applying gentle pressure to gauze sponges on the surface of the wound. Pinpoint electrocoagulation of bleeding vessels by use of bipolar tissue forceps is recommended. Wound Closure After circular excisional biopsy, we routinely undermine the peripheral margins of the defect. With the skin edges elevated by a single hook, the skin margin of the biopsy site is undermined approximately 5 mm using a number 15 knife blade. Undermining the skin edges of defects resulting from circular skin biopsies decreases the forces required for wound closure, which should limit the ultimate width of the scar. Wound closure is accomplished in the same direction as the long axis of the elliptical defect by first approximating the midportion of the defect with a 4-0 synthetic CAPROSYN* monofilament absorbable suture attached to the swage of the laser-drilled, compound-curved reverse cutting edge needle23 Additional interrupted dermal (subcuticular) sutures are placed in each wound quadrant to approximate further the divided edges of the dermis. Sutural closure of the dead space beneath the dermis is contraindicated because these sutures potentiate the development of infection without enhancing wound security. CAPROSYN* suture is the latest innovation in monofilament synthetic suture.23 This suture is prepared from POLYGLYTONE*6211, a synthetic polyester composed of glycolide, caprolactone, trimethylene carbonate, and lactide. An experimental study by Pineros-Fernandez et al.23 compared the biomechanical performance of CAPROSYN* suture to that of CHROMIC GUT sutures. The biomechanical performance studies included quantitative measurements of wound security, strength loss, mass loss, potentiation of infection, tissue drag, knot security, knot rundown as well as suture stiffness. Both CAPROSYN* and CHROMIC GUT sutures provided comparable resistance to wound disruption. Prior to implantation, suture loops of CAPROSYN* had a significantly greater mean breaking strength than suture loops of CHROMIC GUT. Three weeks after implantation of these absorbable suture loops, the sutures had no appreciable strength. The rate of loss of suture mass of these two sutures was similar. As expected, CHROMIC GUT sutures potentiated significantly more infection than did the CAPROSYN* sutures. The handling properties of the CAPROSYN* sutures were far superior to those of the CHROMIC GUT sutures. The smooth surface of the CAPROSYN* sutures encountered lower drag forces than did the CHROMIC GUT sutures. Furthermore, it was much easier to reposition the CAPROSYN* knotted sutures than the knotted CHROMIC GUT sutures. In the case of CHROMIC GUT sutures, it was not possible to reposition a two-throw granny knot. These biomechanical performance studies demonstrated the superior performance of synthetic CAPROSYN* sutures compared to CHROMIC GUT sutures and provide compelling evidence of why CAPROSYN* sutures are an excellent alternative to CHROMIC GUT sutures. Compound-curved reverse cutting edge needles have been specifically designed for dermal closure. The compound-curved needle has two distinct radii of curvature, whereas the standard reverse cutting edge needle has only one. (Fig. 11)  The compound-curved needle has a relatively straight sharpened point with a reverse cutting edge, followed by a curved distal section. The compound-curved needle can be passed through the dermis with greater accuracy to a controlled depth and length of bite than the standard cutting edge needle.24 The passage of the reverse cutting edge needle with a single radius of curvature through dermal issue is not predictable, and its point of emergence through the dermis is difficult to predict. (Fig. 10) In some cases, the point of the needle remains buried in the dermis, becoming a technical challenge to retrieve. These difficulties encountered in the use of a standard needle are overcome by use of the compound-curved needle. The geometric design of the needle allows the physician to position it accurately and repeatedly from the point of needle entry into the dermis and to its exit. The physician can easily predict the site at which its relatively straight point will emerge, allowing the needle to be regrasped by the needle holder for repeated passage through the opposite dermal wound edge. The skin around the edges of the closed skin incision is then coated with tincture of benzoin. Reinforced Steri-Strips are then applied transversely across the incision to facilitate further skin edge approximation. Skin tensions at the wound margins of large defects (>8 mm diameter) may be so great that the skin edges cannot be approximated by dermal and percutaneous sutures. In such cases, coverage of the defect by either a skin graft or local skin flap may be needed. In patients with low skin tensions, it is important to emphasize that sizable wounds, even in the face, have been allowed to heal by contraction (secondary intention) with surprisingly good results. However, most surgeons, especially those with training in reconstructive surgery, close the defect by a graft or local flap without the development of infection or hypertrophic scar formation. Postoperative Care Rigorous follow-up examination is essential for any patient with a history of a skin cancer to detect recurrence and prevent further actinic damage. Much of the morbidity from actinic damage can be prevented by limiting sun exposure and by photoprotection with a sunscreen. The U.S. Food and Drug Administration regulates sunscreen products as over-the-counter drugs.25 Sunscreens are chemical or organic sunlight absorbers and non-chemical or inorganic sunlight absorbers. Other important sunscreen considerations include the sunscreen vehicle, sunscreen photostability, sunscreen preservatives, and sunscreen phototoxicity. Topical and systemic antioxidants have now been shown to supplement the photoprotective effects of sunscreen. The Skin Cancer Foundation, the only national and international organization concerned exclusively with cancer of the skin, is playing a leadership role in eliminating skin cancer in our world. Included below are some important guidelines for sunscreen use that are outlined in Table 1.  DISCUSSION While this narrative description of excisional skin biopsy techniques for skin tumors appears to be relatively simple, it is disappointing that it is not widely used by physicians in our country. The strongest evidence to confirm this belief is that the 10mm trephine is rarely used to excise skin tumors. The limited sales of this product have caused manufacturers of these instruments to not consider manufacturing wider diameter skin trephine biopsies. Most physicians prefer to use the smaller diameter trephine biopsies as an incisional biopsy that leaves a biopsy defect that can be quickly closed with either one or two percutaneous sutures. These trephines are widely used by physicians because the time required for incisional biopsy with a trephine is 10 times faster than the time required for an excisional biopsy made by a No. 15 knife blade. The inability to accept the wide diameter trephine biopsy instrument is due to the fact that most physicians do not have the technical skills to approximate the defect with dermal sutures. Placement of a dermal skin suture necessitates considerable training in a surgical specialty. Consequently, this need for a rapid dermal skin closure technique that can be used by a primary care physician must be devised before the trephine excisional biopsy technique is widely used by the primary care physician. This goal can be achieved by developing a disposable stapler for subcuticular closure of the skin. Such an instrument has been previously described in experimental studies.26 This prototype subcuticular stapler is activated by squeezing its movable handle, causing a pair of gripper blades to approximate and evert the wound edges, after which it pushes one absorbable pin into the dermis. The pin penetrates the dermis twice on both sides of the wound, thus holding the tissue together. Staple wound closure is faster than sutural closure of the dermis. In experimental animals, wounds with staple pin closure exhibited superior resistance of infection than wounds approximated by braided synthetic absorbable dermal sutures. Although sutures provided more immediate wound security than dermal pins, as measured by wound breaking strength, the breaking strength of wounds subjected to dermal pins or dermal sutures was not significantly different 14 days after wounding. Because of early low-breaking strength of wounds closed by dermal pins, the dermal pin closure should be reinforced routinely by application of microporous tapes. In our clinical experience, we have encountered several contraindications to the use of this dermal skin stapler. Because the absorbable pins do not easily penetrate scar tissue, we do not utilize dermal pin closure in wounds with such tissue. Similarly, the thick dermal tissue of the back appears to be resistant to staple penetration, making this tissue refractory to staple dermal closure. Wounds with strong static skin tensions, as evidenced by marked retraction of wound edges, are not easily approximated by pins may dehisce. Finally, there must be a distance of no less that 5 mm from the surface of the dermis to the underlying bone, nerve, or vessel so that the pins can be placed in the dermis without risk of contacting these tissues. This experimental study served as a catalyst for other manufacturers to develop dermal skin staplers that will revolutionize the speed and security of dermal skin closure for excisional biopsy. REFERENCES
|
