Researchers uncover factors that could make melanoma diagnoses easier and surer

Pittsburgh - Researchers at the University of Pittsburgh have identified several factors that could help clinicians more easily differentiate sun-damaged normal skin from that affected by melanoma.

According to the study, reported in the July issue of Archives of Dermatology, these criteria should help prevent over-diagnosis of melanoma and resultant biopsy or surgery that may be unnecessary.

The study notes that lentigo maligna (LM) and LM melanoma (LMM) are characterized by hyperplasia of atypical melanocytes, either singly or in nests, which exhibit a pagetoid spread and extend down the hair follicles. Many of these factors are also seen in normal skin damaged from long-term exposure to the sun.

The distinguishing factors of LM or LM melanoma are nesting, vertical stacking, or pagetoid spread of the melanocytes. Increased melanocyte density, mild to moderate clumping and melanocytes along the follicular epithelium, on the other hand, are normal in sun-damaged skin and not specific to cancer or pre-cancerous lesions.

The researchers studied 132 randomly selected patients undergoing surgery for basal and squamous cell carcinoma of the head and neck during a five-month period in 2003. Using normal but sun-damaged tissue discarded during reconstruction after the tumors were removed, they evaluated the number, density, confluence and depth of melanocytes in the follicular epithelium.

The study found that in normal tissue:

• The mean number of melanocytes per high-power field (equivalent to five mm of skin) was 15.6 (ranging from six to 29). By contrast, undamaged skin has between five and seven.

• Confluence was severe (defined as more than six adjacent melanocytes) in 1 percent of the specimens, moderate (three to six adjacent melanocytes) in 34 percent, mild (fewer than three) in 54 percent and absent in 11 percent.

• Focal areas of increased melanocyte density occurred in 24.2 percent of the specimens. In these areas, the mean number of melanocytes per high-power field was 20.3 (ranging from seven to 36) and the confluence of melanocytes was severe in 13 percent, moderate in 50 percent and mild in 37 percent.

• Melanocytes penetrated the follicular epithelium to a mean depth of 0.38 millimeters.

Significantly, the study reports, there was no pagetoid spread or nesting of melanocytes.