A biopsy, preferably by local excision, should be performed for any suspicious lesions. Suspicious lesions should never be shaved off or cauterized. The specimens should be examined by an experienced pathologist to allow for microstaging.
Studies show that distinguishing between benign pigmented lesions and early melanomas can be difficult, and even experienced dermatopathologists can have differing opinions. To reduce the possibility of misdiagnosis for an individual patient, a second review by an independent qualified pathologist should be considered.[5,6] Agreement between pathologists in the histologic diagnosis of melanomas and benign pigmented lesions has been studied and found to be considerably variable.[5,6]
Evidence (discordance in histologic evaluation):
- One study found that there was discordance on the diagnosis of melanoma versus benign lesions in 37 of 140 cases examined by a panel of experienced dermatopathologists. For the histologic classification of cutaneous melanoma, the highest concordance was attained for Breslow thickness and presence of ulceration, while the agreement was poor for other histologic features such as Clark level of invasion, presence of regression, and lymphocytic infiltration.
- In another study, 38% of cases examined by a panel of expert pathologists had two or more discordant interpretations.
Prognosis is affected by the characteristics of primary and metastatic tumors. The most important prognostic factors have been incorporated into the revised 2009 American Joint Committee on Cancer staging and include the following:[4,7,8,9]
- Thickness and/or level of invasion of the melanoma.
- Mitotic index, defined as mitoses per millimeter.
- Ulceration or bleeding at the primary site.
- Number of regional lymph nodes involved, with distinction of macrometastasis and micrometastasis.
- Systemic metastasis.
- Site-nonvisceral versus lung versus all other visceral sites.
- Elevated serum lactate dehydrogenase level.
Patients who are younger, who are female, and who have melanomas on their extremities generally have better prognoses.[4,7,8,9]
Microscopic satellites, recorded as present or absent, in stage I melanoma may be a poor prognostic histologic factor, but this is controversial. The presence of tumor infiltrating lymphocytes, which may be categorized as brisk, nonbrisk, or absent, is under study as a potential prognostic factor.