Incisional and Excisional Biopsy

The incisional and excisional surgical specimens were evaluated by Drs. Deubner, Argenyi and Oda. The first two specimens revealed large and atypical melanocytes present along the basal cell layer (Fig 3), some were arranged in small clusters (Fig 4). There was evidence of abnormal mitotic figures and linear spreading of the neoplastic melanocytes (Fig 3), as well as evidence of focal superficial invasion in form of a small cluster of the neoplastic cells. The cells were actively producing and releasing melanin pigment. They were negative with S-100 protein antibody and strongly positive with Melan A antibody (Fig 5). The latter is specific for malignant melanoma. Although unusual for malignant melanoma to be negative with S-100, it has been described in 5% of these lesions.

Figure 3.  Low Power (x100) histology shows an H & E stained section showing a piece of gingiva with many atypical melanocytes along the rete pegs spreading upwardly and in a linear fashion.

Figure 4. Higher power (x200) histology shows an H & E stained section showing the gingiva with clusters of malignant melanocytes.

Figure 5.  Low power (x100) histology shows the gingiva from Figures 3 and 4 but stained with immunohistochemistry marker Melan A, a specific antibody that stains malignant melanoma cells. Notice the strong positive staining denoted by the dark brown color.