What type of biopsy should be performed for a pigmented lesion suspicious for melanoma?
Biopsy of a suspicious pigmented lesion aims to establish a diagnosis and to stage the tumour for planning definitive surgical therapy. In addition, an excisional biopsy may completely remove the tumour. Different methods of biopsy are variably effective in achieving these goals and it is important to choose the most appropriate method according to the aims of the biopsy, the site and size of the lesion, the index of suspicion for melanoma, the likelihood of invasive tumour, and patient factors including comorbidities, cosmesis and age.
Summary of systematic review results
Complete excisional biopsies
Elliptical Excision and Primary Closure
The ideal method for skin lesions suspected of being melanoma is complete excision with a 2 mm margin. An ellipse specimen should follow the lines of relaxed skin tension with the deep margin in subcutis. Primary closure is the preferred method of closure following excisional biopsy and skin flaps or grafts should be avoided because these may compromise the definitive re-excision.
Complete excision best facilitates accurate diagnosis and microstaging compared to partial biopsy techniques. 
Deep Shave excision (Saucerisation) and punch excision
Deep shave excision (Saucerisation, scoop shave excision) and punch excision methods (e.g. 5 mm punch for a 3 mm lesion) may also be used for complete excision but are more often associated with positive margins than elliptical excision and primary closure. Deep shave excision may be defined as a shave excision that aims to completely remove the lesion both peripherally and in depth. However, skill and practice are required to perform the procedure effectively.
Attempts at deep shave excision will more often completely remove thin melanomas and are more likely to transect the tumour margins with increasing tumour thickness. Transection of the tumour base will lead to loss of limited amounts of residual tumour that may be destroyed by inflammation and wound healing and may undermine the capacity to accurately assess tumour depth for prognostication, accurate staging and treatment planning.
Deep shave excision is becoming more widely used and in most recent studies was the dominant mode of biopsy for melanoma, particularly by dermatologists worldwide. Transection of the tumour base has been shown to be common with shave biopsy in recent studies (68%, 32%, 62%, 65%, 9%, 37% in studies from Egnatios, Hieken, Lowe, Mills, Mir and Zager respectively), though the extent to which these shaves were attempting to completely remove the tumour were generally not stated.
Deep shave excision has the advantages of being relatively speedy, inexpensive and requiring little equipment or staff assistance. The procedure thus allows the conduct of greater numbers of biopsies, including lesions with lower indices of suspicion. Delays are minimized in the conduct of biopsy procedures as many deep shaves are conducted as part of the consultation and do not require another appointment. The technique requires careful lesion selection and expertise in conduct to avoid base transection, a serious and too frequently evident drawback with use of this method. In general the technique should be limited to non-palpable lesions. If a clinician cannot be confident of complete removal of the deepest part of the lesion a full excisional biopsy should be undertaken.
Methods of partial biopsy that have been assessed include partial punch biopsy, shave biopsy and, to a lesser extent, incisional biopsy. At times partial biopsy may be the most appropriate mode of biopsy for large lesions, those on acral sites or other difficult locations where an excisional biopsy may have unwanted functional or cosmetic outcomes or in patients with significant comorbidities.
The most important outcome of a partial biopsy is accurate diagnosis. One large study has compared melanoma biopsy methods for the detection of melanoma. This study showed that punch biopsy is associated with a false negative diagnosis rate of 23.3% compared with 4.5% for all shave biopsies and 1.7% for excisional biopsy. Adverse outcomes with persistence or progression of disease followed 11.6% of false negative diagnoses on punch biopsy and 1.7% following shave biopsy. Most of these false negative diagnoses and adverse outcomes would have been avoided if all lesions clinically suspected as melanoma that had then been shown to be melanocytic on biopsy had been immediately subjected to excisional biopsy. Most (78%) of incorrect diagnoses made on small punch biopsies were attributable to errors in histopathological interpretation and the remainder appeared to be due to sampling error. Partial biopsies may lead to pathological incorrect interpretation because it is not possible to assess important diagnostic criteria when the whole lesion is not available for assessment.
Accurate staging of the tumour on partial biopsy permits prognostication and planning of appropriate surgical therapy for the primary tumour. Understaging of melanoma as a result of partial biopsy has been examined in multiple studies. Increases in tumour thickness on assessment of residual melanoma in wide local excision (WLE) after a partial biopsy were shown after 3.5%-44% of shave and 34%-38% of punch biopsies. The variation may be explained by differing intentions on the part of the clinicians to partially or completely remove the tumour in the initial biopsy procedure.
Not all understaging of melanoma may be evident on the subsequent wide excision as diathermy used in the procedure or destruction of tumour by inflammation may destroy underlying tumour in the biopsy bed.
Deep shave excision (saucerisation) should be distinguished from superficial shave techniques which are generally used for partial biopsy. The latter are most appropriately applied to flat lesions that appear to be in situ. Shave biopsies of all types have been shown to be associated with very high rates of transection (64-65%) of the tumour base in some studies. When shave excision is applied to thin melanomas (<1.0 mm in tumour thickness), rates of base transection are much lower (9-21%) with very few melanomas upstaged on WLE. Several studies have shown a relationship between base transection and increasing tumour thickness. These studies do not distinguish attempts at deep shave excision from superficial shave for partial biopsy.
There are no studies to date of the morbidity and cosmetic outcomes associated with different biopsy types.
All partial biopsies should include the most suspicious or invasive areas of the lesion. Dermoscopy or confocal microscopy may be helpful in targeting the most suspicious area.
It may be appropriate to indicate in the pathology report that a partial biopsy may not be fully representative of the lesion.
Partial biopsies are an important cause of litigation in the USA because of inadequate material being available for analysis by the pathologist.
Naevoid melanomas and desmoplastic melanomas may be extremely difficult to diagnose histopathologically, particularly on a small biopsy.
It is important to consider the weaknesses of partial biopsies when interpreting the pathologist’s report. If the result does not accord with the clinical impression or there is diagnostic uncertainty, an additional sample should be obtained, preferably by performing a complete excision. This is especially important when the histopathological diagnosis from a partial biopsy is of a melanocytic lesion.
Clinical information for the pathology request to facilitate accurate histopathological diagnosis
All biopsy requests should include information on history of lesional changes, site of the lesion, age and gender of the patient and previous melanoma history. Any previous trauma or attempted therapeutic intervention to the lesion should be noted. If possible, the provision of clinical and dermoscopic images to the pathologist have been shown to enhance accuracy of histopathological diagnosis.
The biopsy type and proportion of the lesion sampled should be indicated. Focally suspicious areas within a larger lesion can be indicated on a diagram or photograph or marked for the pathologist e.g. with superficial punch incision.
Indications for different modes of partial biopsy
Partial incisional or shave biopsies may be appropriate in the hands of experienced clinicians and in carefully selected clinical circumstances, such as large in situ or for large facial or acral lesions or where the suspicion of melanoma is low.
An incisional, partial punch biopsy provides dermis and often subcutis for assessment of tumour thickness but samples only a limited width of the lesion and is therefore prone to sampling error as well as diagnostic error. Punch biopsy should be avoided if there is any possibility of melanoma because of the high rates of false negative diagnosis demonstrated with partial punch technique. Multiple punch biopsies may reduce error in selected cases.
A broad superficial shave biopsy can provide a larger area of epidermis for histopathology and is often a useful diagnostic technique for large superficial lesions, but often fails to include sufficient dermis for the assessment of deeper parts of lesions with a significant dermal component. These biopsies may be considered for lesions that are likely to be confined to the epidermis (e.g. when attempting to differentiate in-situ melanoma from solar lentigo or seborrheic keratosis or a flat acquired melanocytic naevus). In order to maintain the integrity of the epidermis on the sample, at least papillary dermis must be present across the shave. Superficial shave biopsies taken through papillary dermis heal with little or no scar and are therefore suitable for use on the face. A photograph to identify the biopsy site should be used for superficial shave biopsies in cases for which it may not be possible to identify the biopsy site when it has healed.
Incisional biopsy removing as much of the lesion as is feasible or the most invasive or suspicious part can be a very useful method of partial biopsy in larger tumours.
Frozen section and cytological analysis are inappropriate for suspicious pigmented lesions, but may be of value (particularly fine needle biopsy cytology) when assessing potential metastases from a melanoma, for example, in a lymph node or subcutaneous tissue.
When clinical suspicion of malignancy is low and there is no elevation or induration to suggest possible invasive melanoma, short term observation for 3-6 months may be appropriate, preferably backed up by a dermoscopic image, a clinical image and an accurate description and measurement of the lesion.
Referral to a specialist should be considered before biopsy for lesions in technically difficult anatomical locations (e.g. the eyelid) or where the operator is not confident in achieving an adequate sample or good cosmetic result. The specialist to whom the referral is being made should be advised directly of the degree of urgency.
Where clinical suspicion remains despite a negative pathology report following a partial biopsy, re-biopsy or excision should be performed. Even after complete excision, if the pathology result does not correlate with the clinical impression, discussion of the case with the pathologist is recommended. Review of the slides by a second pathologist may be appropriate if clinical suspicion remains or if there is diagnostic uncertainty.
Evidence summary and recommendations
|Partial biopsies versus completeness of excision
Complete excision with a 2mm margin is the most reliable diagnostic biopsy method for skin lesions suspected of being melanoma.
|Punch biopsy has been shown in one large study to be associated with high rates of false negative histopathological diagnosis of 23% and should be used with caution for melanocytic lesions.||III-2|||
|Deep shave excision (saucerisation) is more likely to accurately stage the melanoma if it is in situ or superficially invasive than if it is more deeply invasive.||III-2, IV||, , |
|Partial biopsy has been shown to underestimate T-stage in 7-34% of punch biopsies and 3-19% of shave biopsies and provides insufficient information for appropriate surgical planning in 18% of punch biopsies and 3-5% of shave biopsies.||III-2, IV||, , , , , |
|Survival and the performance and outcomes of sentinel node biopsy show no differences according to partial versus complete excisional biopsy type.||III-2, IV||, , , , |
|The optimal biopsy approach for a suspicious pigmented lesion is complete excision with a 2 mm clinical margin and upper subcutis.||C|
|Partial biopsies may not be fully representative of the lesion and need to be interpreted with caution and in light of the clinical findings to minimise incorrect false negative diagnoses and understaging.||C|
It is advisable to discuss unexpected pathology results with the reporting pathologist.
The use of deep shave excision (saucerisation) should be limited to in situ or superficially invasive melanomas to preserve prognostic features and optimise accurate planning of therapy.
Issues requiring more clinical research
A better understanding of the role of deep shave excision (saucerisation) and superficial shave biopsy is needed.
Future studies are needed that clearly define the intention of the biopsying clinician to partially or completely biopsy each lesion. The index of clinical suspicion for each lesion would be helpful to further understand the intention of the clinician. Studies should include a clear description of the intended biopsy method to distinguish superficial shave biopsy from deep shave excision (saucerisation) and partial punch incision from punch excision. The presently available studies are retrospective and because they group attempts at partial or complete biopsy by different methods, results vary widely.
Studies that evaluate the morbidity and cosmetic outcomes associated with different biopsy types are also needed.
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