Vertical Growth 2
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Melanocytic Neoplasia

(“lichenoid” reaction)

Fig. 15a

In this area (same lesion as Fig. 9), the epidermal component is partly represented. Even with this limited representation, there is the outline of a defect that could represent lysis of an elongated rete ridge. The defect could also represent an area in which a junctional nest of neoplastic melanocytic has undergone immune-mediated regression. The neighboring stroma is delicate and infiltrated with lymphoid cells. The cells in the junctional defect are loosely attached to their neighbors; lymphoid cells are represented among the cells. At least one cell is dendritic in outline and has a prominent nucleolus; it is interpreted as a neoplastic melanocyte. This is the histologic of a  cell-mediated immune reaction; the patterns are the homologue of changes in a lichenoid reaction with the exception that the target cell is a neoplastic melanocyte. The loose stroma is richly vascularized.

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Fig. 15b

On the right, rete patterns are partially preserved; the dysplasia is represented at the dermal-epidermal interface. A band-like, but somwhat loose, infiltrate of lymphocytes fills the widened papillary dermis. On the left, the rete patterns are effaced; the dysplasia is not represented; and the lymphoid infiltrates have resolved. The papillary dermis to the left of the center of the field is widened and fibrotic. The melanocytic process has regressed in continuity over a broad expanse. The result during this interval of susceptibility has been partial regression. It should be emphasized that what has regressed may have been something more advanced neoplastically than what remains on the right. There is regression and, in this shadow of what was, the possibility that a vertical growth component may have been represented cannot be ruled out. The patient should be examined and followed for evidence of metastatic disease. A biopsy of a sentinel node should be considered. The complicated patterns qualify the lesion as a borderline process of indeterminate biologic potential.

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MDM

(nevoid type showing typical vertical growth

Fig. 16

In this field (same lesion as Figs. 10 & 13), two closely spaced nodules of typical vertical growth are represented. The nests of cells are closely aggregated and, in clusters, form expansile nodules. Some of the cells are pigmented and there are scattered melanophages. The pattern in the epidermis is that of a senescent lichenoid reaction. In addition, the papillary dermis is widened and fibrotic - an additional quality that contributes to the pattern of a senescent lichenoid reaction. As an explanation for the combination of features, the lichenoid changes could represent a marker in which a lentiginous and junctional component has regressed. The nodule in the dermis is apparently confined at level III; in addition, and in support of a level III pattern,a band of condensed fibrous tissue outlines the nodule at its interface with the reticular dermis. There are nevus-like patterns to the right of the smaller nodule.

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MDM

(typical vertical growth)

Fig. 17

In this more advanced pattern of growth, the clustered nests of atypical melanocytic cells form an expansile nodule that appears to sit upon the reticular dermis. In the 60’s, there was an attempt to include advanced lesions showing this pattern in the category of “superificial melanoma” with the implication that such lesions would have a better prognosis. Such was not the case and the category of “superficial melanoma” was discarded. By size, along the vertical axis in the “thickest” area, this pattern is appropriatedly characterized as melanoma without attention to the depth of invasion into the dermis. The patterns to the left of the nodule are in keeping with those of partial regression.

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MDM

(typical vertial growth)

Fig. 18

In this field (same lesion as Fig. 16), small nests and individual tumor cells infiltrate the reticular dermis among collagen bundles of the reticular dermis. Inflammatory infiltrates are not associated with this population of neoplastic migrants. The cells have abandoned the security of a community of cells (level III invasion) for the hazards of a migration (level IV invasion; level IV pattern0.

In this more advanced pattern of growth, the clustered small nests and the individual cells form an ill-defined, small expansile nodule. In this limited area, it is by pattern, rather than its small size, tjat such an area can be appropriately characterized as melanoma. Obviously, this is level IV invasion; it is representative of a more advanced pattern of neoplastic progression; the cells have acquired the properties of universal migrants. The patient should be examined and followed. Some consideration should be given to sentinel node biopsy.

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