DERMATOPATHOLOGY AN EDUCATIONAL GUIDE

Transcription

1 DERMATOPATHOLOGY AN EDUCATIONAL GUIDE

2 INTRODUCTION Skin conditions (in particular skin tumours) represent the most common histopathology specimens received by the pathology laboratory. In view of Australia s climatic conditions, skin tumours are very common. Of all the organ systems, the skin has the greatest number of lesions described, perhaps because the skin is subject to a wide variety of environmental exposures and no special procedures are necessary to visualise its surface. The diagnosis of skin conditions and tumours is a joint effort between the patient, clinician and pathologist. The more information available to the pathologist, the greater their ability to establish the correct diagnosis. CLINICAL HISTORY This is of the utmost importance in the diagnosis of skin conditions. In some cases (particularly in inflammatory skin conditions) the histological appearances seen under the microscope can be seen in a group of conditions. The history should include: site, size, duration, appearance, symptoms, relevant medical history (ie. systemic disease, immunosuppression), medications and clinician differential diagnosis. Previous biopsy results and treatment are also important. SKIN BIOPSIES INDICATIONS (see Table 1) Skin biopsies are an essential technique in the management of skin diseases and can enhance the dermatological care rendered by doctors. A skin biopsy is most frequently performed to diagnose a skin growth such as mole, or skin condition such as a rash (particularly if not easily diagnosed with the naked eye). They are useful in all suspicious masses/neoplasms (eg. cancer of the skin). A skin biopsy may be indicated when a mole or other marking on the skin has changed its shape, colour or size. A skin biopsy is also sometimes used to diagnose infections of the skin. When a skin condition persists despite treatment, a biopsy should be considered. Skin lesions that have been surgically removed should always be sent to the pathology laboratory for examination. CONTRAINDICATIONS There are few absolute contraindications to skin biopsy, but all patients should be told that biopsies leave scars, with particular emphasis on lesions on the face. In most cases a biopsy should be avoided at an infected site, although occasionally infection may be an indication for the procedure. Inquiry of the patient should be made regarding allergies to topical antibiotics, antiseptics, local anesthetics and reactions to tape. Patients should be asked about bleeding disorders, bleeding with previous surgery, and use of drugs known to interfere with haemostasis. Particular care must be taken with patients who have bleeding disorders or who are taking warfarin, and specialist referral could be considered. Patients taking aspirin can generally be managed with careful attention to haemostasis and the use of pressure dressings. TABLE 1 : INDICATIONS FOR SKIN BIOPSY INDICATION CLINICAL PRESENTATION POSSIBLE DIAGNOSIS BIOPSY TECHNIQUE Diagnosis Rashes or blisters Involving dermis Drug reaction Cutaneous lymphoma Deep tissue infection Panniculitis Lupus erythematosis Pemphigold Pemphigus Psoriasis Vasculitis Punch Process involving the subcutis Panniculitis Punch Diagnosis and treatment Atypical moles and pigmented lesions Dysplastic naevi Malignant melanoma Actinic keratosis Basal cell carcinoma Seborrheic keratosis Pyogenic granuloma Skin tags Squamous cell carcinoma Excision or punch for small lesions. Shave biopsy may be considered in large superficial lesions, e.g. lentigo maligna

3 SITE SELECTION One of the more difficult initial decisions is selecting the biopsy site. For inflammatory conditions the earlier the lesion, the more specific the histopathology. Consequently, only the newest vesicles and blisters should be biopsied, usually within 48 hours of their appearance. Older lesions with secondary changes such as crust, fissures, erosions, excoriations, and ulceration should be avoided, since the primary pathological process may be obscured. Whenever possible, remove vesicles intact, with adjacent normal-appearing skin, because disruption makes histological interpretation more difficult. For non-bullous lesions, the biopsy should include maximal lesional skin and at least a small amount of normal skin if possible. Bullae should be biopsied at their edge, keeping the blister roof intact. For lesions between 1mm and 4mm in diameter, biopsy the centre or excise the entire lesion. For larger lesions, biopsy the edge, the thickest portion, or the area that is most abnormal in colour, because these sites will most likely contain the distinctive pathology. If the differential diagnosis is broad, biopsy several sites to minimize sampling error. Hypertrophic scarring tends to occur over the deltoid and chest area, and delayed healing can be a problem over the tibia, especially in diabetic patients or in patients with arterial or venous insufficiency. The influence of secondary infection in the groin and axillae is high, therefore biopsy these areas only if other sites are unavailable. TYPE OF BIOPIES 1: Shave biopsy lesions that are entirely above the skin surface can be shaved off as a tangential excision using a No.10 scalpel blade or the flexible DermaBlade. (see figure 1) Typical lesions removed this way include large skin tags, filiform warts, seborrhoeic keratosis, paillomatous melanocytic naevi, cutaneous horn and hyperkeratotic solar keratosis. This technique may also be used to sample: a flat skin lesion such as possible basal cell carcinoma in-situ squamous cell carcinoma lentigo manligna pigmented macule mycosis fungoides dermatoses This is best done with removal of 4mm of tissue from the active edge of the lesion. Light cautery or other methods of haemostasis may be used and the wound left to heal secondary intention. Shave biopsies however are best avoided for suspicious pigmented lesions. 2: Punch biopsy - a full thickness skin core extending into the deep dermis and subcutis. (see figure 2) A punch biopsy is used to obtain a diagnostic full-thickness specimen from: a dermatosis suspicious raised pigmented lesion annular lesion alopecia/hair loss neoplasm for the removal of a small lesion They are simple to perform, have few complications, and if small, can heal without suturing. The punch biopsy involves the use of a circular blade or trephine attached to a pencil-like handle. Biopsy punches may have blades of diameter 2mm to 10mm; disposable 3mm to 4mm blades are the most useful. The technique is like using a miniature biscuit cutter. The punch biopsy yields a cylindrical core of tissue that must be gently handled to prevent crush artefact. It is better to extract it with a needle than to use forceps. Avoid using 2mm punches as they provide little tissue and commonly cause crush artefact of tissue, compromising diagnosis. It is preferable to use a 4mm or larger punch. FIGURE 1: TYPICAL LESIONS REMOVED OR DIAGNOSED BY SHAVE BIOSPY FIGURE 2: TYPICAL LESIONS REMOVED OR DIAGNOSED BY PUNCH BIOSPY FIGURE 3: TYPICAL LESIONS REMOVED OR DIAGNOSED BY CURETTAGE BIOSPY

4 If taking a biopsy of an inflammatory dermatosis, consider whether a pathological diagnosis (which may be nonspecific) will change management. If possible, avoid the lower leg and ulcerated, eroded or excoriated lesions. Choose a lesion of recent onset or the most abnormallooking edge of an enlarging plaque. A separate punch biopsy may be taken from perilesional skin for direct immunofluorescence in case of a blistering disease or suspected lupus or vasculitis, or from the centre of the lesion for culture in case of suspected mycobacterial or deep fungal infection. The technique is not recommended for suspicious melanocytic lesions. These are better excised as sampling could miss melanoma (especially for those that have arisen within a benign lesion). 3: Curettage Superficial scraping of a skin lesion. Curettage refers to the use of a sharp spoon-like instrument to scrape off a predominantly epidermal superficial skin lesion. The lesion may be shaved off flush with the skin. (see figure 3) This technique is useful for raised friable lesions that are easily scraped from the skin surface. Curettage can be used for the following skin lesions: Viral warts (if failed to resolved with salicylic acid) Molluscum contagiosum (in adults) Seborrhoeic keratoses Pyogenic granuloma Solar keratoses In-situ squamous cell carcinoma (Bowen s disease) Superifical basal cell carcinoma (in experienced hands) Well demarcated and small nodular and cystic basal cell carcinoma Occasionally curettage may be followed by cryotherapy or photodynamic therapy. Diathermy or cautery may be used to de-bulk a large skin tumor prior to formal excision biopsy of the defect. Curettage is inappropriate for infiltrating or dermal tumours. It should not be used for poorly differentiated squamous cell carcinoma or for melanocytic lesions. A basal or squamous cell carcinoma is generally removed with a 4mm margin as the tumour is generally larger than clinically evident. PIGMENTED LESIONS An important caveat regarding removal of pigmented skin lesions is the possibility of malignant melanoma. With this in mind, small lesions indicative of melanoma can be removed by punch biopsy, provided that the lesion can be completely removed, whereas larger lesions require an excisional technique. In either case, complete removal in width and depth allows proper staging in the event that it is melanoma. As a corollary, such pigmented lesions should not be destroyed by cryosurgery or partially removed (if possible) by shave biopsy because this impairs the ability to make an accurate diagnosis or properly stage the tumour. If a melanoma is diagnosed, the amount of tumour free margin is determined by the depth of tumour invasion (tumour thickness). In practical terms, this means that the original excision may need to be revised, usually creating wider tumour margins laterally and deeply, even if the margins of the original biopsy are free of tumour. Medical practitioners with less experience may consider referring the patient for further management. BIOPSY SITE TIPS Tumours sample thickened area. Avoid inflamed and scarred areas. Rash Biopsy edge of blister with adjacent normal skin edge of annular lesion, and biopsy multiple sites (2-3) of popular rash. LANGER S LINES (See figure 4) Langer s lines, sometimes called cleavage lines, are topographical lines drawn on a map of the human body. They correspond to the direction in which the skin of a human cadaver will split when struck with a spike. FIGURE 4: LANGER S LINES 4: Incisional biopsy partial sampling of lesion. Useful for same conditions as punch biopsy. 5: Excisional biopsy total removal of lesion. Usually larger and deeper and used to completely remove an abnormal area of skin (such as skin cancer). This techniques if best used for suspicious lesions where it is likely that excision will ultimately be required (e.g. melanoma, carcinoma). The margin of the lesion should be identified in good light, possibly using magnification. Suspected melanomas should be excised with a 2-3mm margin initially. Narrow margins are recommended for melanocytic lesions for the following reasons: Definitive excision margins of confirmed melanoma are selected according to the histological depth of the tumour Minimal cost and risk of complications and scarring should the lesion prove benign.

5 USE OF LANGER S LINES Knowing the direction of Langer s lines with a specific area of skin is important for surgical operations, particular cosmetic surgery. If a surgeon has a choice about where and in which direction to place an incision, they may choose to cut in the direction of Langer s lines. Incisions parallel to Langer s lines may heal better and produce less scarring than those that cut across them. SIMPLE TIP FOR DETETMINATION OF LANGER S LINES (see figure 5) Gently compress/pinch skin between thumb and forefinger in different directions. Where the skin folds easily is generally the line of cleavage (Langer s line). On the face wrinkle lines are a good indicator. FIGURE 5: WRINKLE AND SKIN FOLDS ARE A GOOD INDICATOR OF LINES OF CLEAVAGE Specimens that are required to be received fresh (for immunofluorescence, microbiology or flow cytometry) are to be submitted in saline-dampened sterile gauze in a sterile container and sent urgently to the laboratory (arrange urgent courier pickup). Immunofluorescence is useful in the diagnosis of inflammatory skin conditions, bullous skin disease and some types of vasculitis. Microbiology should be considered in cases of inflamed, ulcerated, granulomatous, nodular or popular lesions of uncertain aetiology. Consider requesting fungal or mycobacterial culture. Flow cytometry/gene rearrangement studies should be considered in cases of suspected lymphoma. Often separate fresh tissue is recommended (with this being frozen in the laboratory, until it is determined as to whether such studies are required or not). ORIENTATION In the case of large punch or incisional/excisional biopsies, orientation of specimen should be considered, particularly if there s a concern that the tumour is close to a margin. This orientation will enable the pathologist to determine which margins are involved if the tumor/lesion reaches the margins. This is best done with a marking suture at one pole or edge, with the location of the suture being stated on the request form (e.g. suture at 12 o clock). This could also be done with a diagram. (see figure 6) FIGURE 6: MARKING SUTURE SURGICAL PRINCIPALS SKIN PREPARATION Shave, punch and curettage are clean but not sterile procedures, whereas excisional biopsy is a sterile procedure. The skin should be prepped with alcohol or iodine. Mark the lesion prior to injecting with anaesthetic if small or subtle, as the swelling from the anaesthetic may mask the lesion. ANAESTHESIA The following anaesthetics are recommended: 1-2% lignocaine. Adrenalin 1:100,000 increases duration of anaesthetic and haemostasis (BUT DO NOT USE ON DIGITAL OR PENILE BIOPSIES). Be careful on nose and ear. HAEMOSTASIS Pressure, aluminium chloride (Drysol, Gelfoam), Monsel s solution and electrodessication (cautery) are all methods that can be used. SUBMISSION OF SPECIMEN Routine specimens are to be placed in 10% buffered formalin. Each specimen should be placed into a separately identified, labelled specimen container. Specimens need to be adequately labelled with at least two patient identifiers on the label (eg: name and date of birth), and with site and side of lesion. IN THE LABORATORY After the biopsy, the skin is fixed in special solution (usually formalin) and then processed. Thin sections of the tissue are cut and placed on microscope slides. The slides are stained for examination by the pathologist and a report is produced. Sometimes special stains are used to examine for antibodies, immune proteins or other markers of certain diseases. REPORT TURNAROUND TIME This is dependent on the complexity of the lesion/process. In general, straightforward cases are reported within 48 hours from the time arrival at the laboratory. If the case is complex or special stains and immunohistochemistry are required more time may be needed. In exceptional, difficult cases, a further specialist opinion may be sought, resulting in a further delay.

6 DOREVITCH SKIN SPECIALISTS Our pathologists are the difference Experienced. Trustworthy. Consultative. Dr Joel Pinczewski MD(USA) PhD FRCPA Dr Paul Kerdemelidis MB ChB Dip Obst FRCPA Dr Teong H. Saw MBBS(Qld) FRACGP FRCPA Dr Iman Alash MBChB MScPath FRCPA Dr Mikkaela McCormack MBBS LLB FRCPA Dr Siew-Khin (Happy) Tang MBBS FRCPA FIAC Dip. Cytopath Dr Elham Amini MD FRCPA Dr Christine McTigue MB BS(Syd) FRCPA Dr Alan Wong MBBS FRCPA Dr Gregory Imhagwe MBBS FRCPA Dr Alex Nirenberg MBBS BSc FRCPA FRCPath FIAC Diploma in Dermatopathology Dr Leonard Wu B.Med PhD FRCPA Dr Anusha Kapoor MBBS DCP DNB FRCPA Dr Aurelia Sadauskiene MD AMC FRCPA 18 Banksia Street, Heidelberg VIC 3084 Ph (03) Fax (03) dorevitch.com.au