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c9t3P1: pigmented spindle cells form closely aggregated fascicles; the cells are heavily pigmented. Stroma is scanty. There is moderate atypia; nuclear features are monotonous. There are clusters of melanophages. Some observers might find features of “malignant blue nevus” in such a pattern.
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c9t3P2: plump, spindle and “epithelioid” cells form closely spaced fascicles in a delicate fibrous matrix. The cells have lavender cytoplasm, but great emphasis should not be placed on this quality; the stain is old. Nuclei are plump and vary in size. Chromatin is marginated; nuclear membranes are “heavy.” The cells are loosely attached to their neighbors; the nests are cavitated. There are clusters of melanophages.
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c9t3P3: above the center of the field, heavily pigmented melanophages are clustered; viable tumor is not represented in this area. Below the center of the field, atypical cells form closely spaced, rounded nests. The pattern has qualities of a level III, typical vertical growth component, but this cluster of nests is isolated in the reticular dermis. A multinodular pattern at advancing margins is a feature of the vertical growth component of some ALM. In this example, the cells are large, and loosely attached to their neighbors. There are scattered, multinucleated giant cells. The pattern in the micronodule is pleomorphic. Some of these lesions show prominent patterns of regression with melanoderma; I cannot rule out the possibility that some of the lesions were perfused prior to excision.
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