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c16t3P1 (case 1374) : the pattern in this field is classic arrested variant vertical growth. The epidermis is hyperplastic with the pattern being that of hyperplasia of the superficial unit. There are focal lentiginous and junctional patterns. The dermal component is confined to a widened, fibrotic papillary dermis. The pattern is that of a level III lesion.There are mild perivascular infiltrates of lymphoid cells. The nests of cells in the papillary dermis are mostly rounded in outline. The cells forming the nests are variably pigmented. The lesion is thin, but shows a variant vertical growth pattern; the lesion is a thin melanoma. It measured 0.6 mm in vertical dimensions, but there were metastases at the time of diagnosis.
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c16t3P2:In this field, the patterns are similar. There is upward migration of atypical cells into the epidermis. The cytologic atypia is marked; it is of the type seen in the pattern of the common final pathway (it is of the type seen in classic lesions of SSM). In the dermis, nests of atypical cells are loosely spaced in a laminated fibrous matrix; the pattern is that of arrested variant growth.
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c16t3P3: Cytologic atypia is marked; the cells are rounded and plump. Cytoplasms are finely pigmented. There are focal areas of lamellar fibrosis. The lesion measured 0.6 mm in vertical dimensions. There were “metastases” at the time of the original surgery. To the left, the lesion shows a pattern of arrested variant vertical growth; the fibrous lamellae which entrap the nests of cells are a defining feature of arrested vertical growth. To the right, the matrix is delicate; the arrested pattern is not represented; the patterns to the right probably represent early typical vertical growth. In these early stages, distinctions are hard to define.
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c16t3P4 (case 1593): This is a different lesion. In the radial growth component, the pattern is that of a high grade dysplasia; nesting, rather than lentiginous patterns, are preponderant. In the nests, there is loss of cellular cohesion. Individual cells and nests of cells have migrated upward into the epidermis. Lymphoid infiltrates are moderate. The papillary dermis is widened and fibrotic. There are occasional nests of pigmented cells in the widened papillary dermis. By Clark’s criteria, the lesion in this field could be characterized as SSM at level II. By other criteria, it would qualify as microinvasive melanoma. In the concept of MDM, the pattern in this field is compound, marked melanocytic dysplasia (pattern of common final pathway, borderline neoplasia of indeterminate malignant potential).
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c16t3P5: In this field, the nests of cells in the dermis are loosely, but regularly, spaced in a widened papillary dermis (level III pattern). On the basis of degree of atypia, the lesion might be characterized as SSM at level III. The papillary dermis is delicate, and the patterns have an organoid (nevoid) quality. The cells form nests and fascicles. The lesion measured 0.69 mm in vertical dimensions; it recurred locally. The demonstration of patterns for this case are continued in the next chapter (c17t3P1).
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