There is widespread, consolidated consensus that the best method for removal of a melanoma is a full thickness excision of the entire growth along with a ring of normal skin surrounding the melanoma. This is because reliable staging and histology (cell type, pattern, growth) depends on having an intact specimen. It also allows for removal of possible non-visible melanoma spread beyond the spot. Additionally, the decision needs to made as to whether the patient would benefit from sentinel lymph node biopsy (SNLB) since this needs to be performed before surgical excision. The AJCC and the WHO both recommend SLNB for tumors greater than 1 mm thick. Additionally, if the tumor is less than 1 mm thick but is ulcerated or has evidence of vascular/lymphatic invasion, SLNB should be done.
Current margins of excision have been based on the results of several randomized studies. The margin of excision is the amount of skin and underlying subcutaneous adipose tissue around the tumor that is removed in addition to the tumor itself. Tumors of less than or equal to 1 mm thick are generally excised with a 1 cm radial margin of excision. Tumors of 2- 4 mm thickness require a 2 cm circular margin. Tumors greater than 4 mm thick generally are removed with a 2 cm margin. It is important that a 1-2 cm circle of normal skin is removed to account for the possibility of microsatellites (very small clusters of melanoma cells outside of the main tumor that may grow into new tumors) since melanoma may extend to where it is not visible. Narrower margins are acceptable for in situ melanomas and should be at least 5 mm in width to decrease the chance of local recurrence.
It should be noted that controversy exists as to whether tumors greater than 2 mm thickness should have a 2 or 3 cm margin removed. Some medical centers prefer the 3 cm margin due to a lower possibility of local reccurance, but studies have only been done on differences between 1 and 3 cm margins, not 2 cm margins (Barclay, 2004). It is safe to say that a 1 cm margin for a tumor greater than 2 mm is not acceptable practice. Whether your surgeon chooses a 2 or 3 cm margin is based on the preference of the surgeon and institution and until further studies are completed, both practices are acceptable.
Incisional biopsies (punch, shave, scoop) where a portion of the skin spot is removed are not recommended. However, there are a few situations where incisional biopsy is warranted. If the spot is large and on the face, head or neck and removal would be disfiguring or disrupt the function of anatomical features it is recommended to remove a full thickness portion of the spot that includes some normal skin for biopsy. If there is a low suspicion that the spot is melanoma or it is in the nail bed, an incisional biopsy may be done.
Large facial melanomas, especially of the lentigo maligna variety (a sub-type of melanoma in-situ), may have cancerous finger-like extensions under or on the skin that are not visible on the surface. Removing a large lesion with the appropriate margin on the face poses problems with interrupting anatomic features (eyes, mouth, nose) and gross disfigurement. An alternate technique being performed at St. Louis University termed “Slow Mohs” consists of first removing a 5mm (or 0.5cm) ring of “normal” tissue around the melanoma. The melanoma is initially left untouched. The entire tissue ring is then sectioned and sent to the histopathology lab to determine if cancer cells extend beyond the surface skin spot. If so, another portion of skin is removed in the affected area and sent for laboratory examination. Once the margins are deemed clear, the central portion or the original area of the melanoma is then removed at the time of the final reconstruction. The advantages of this technique are sparing of anatomic features, less tissue removal, and more accurate histopathologic margin assessment of non-visible cancer spread.
There is ongoing debate as to the use of Mohs surgery in melanoma. Arguments for Mohs surgery are the more accurate pathologic margin assessment, the possible smaller wound size and sparing of tissue. Cons to Mohs surgery are the difficulty in Breslow’s staging if a full-thickness piece is not removed, the use of frozen biopsy sections that may cause frozen artifact and further difficulty in staging rather than longer staining techniques, and the possibility of missing satellite cancer cells that are distant to the primary tumor since a wider swath of normal tissue is not removed.
Larger excision margins (3-5 cm) that were common in the 1970’s are no longer used because they did not increase life span and added to the costs and morbidity of patients.