Whithers 1

Whithers 2

Whithers 3

Desmomela

BWEEMS

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MDMLMM

Nevoid MDM

MDMhalo

Nearneoplasia

MDMhalo, metastasizing

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Pictorial 1

Pictorial 2

Pictorial 3

Pictorial 4

This site is C5P2 and is dedicated to an exposition of halo nevus-like phenomena in the dermal component of the lesion in question. For this presentation, some conceptual preparations are required. The patterns of halo nevus-like phenomena embrace those of a cell-mediated immune reaction. Eosinophils and small aggregates of epithelioid histiocytes are sometimes included. Plasma cells, if represented, are likely to be found at the periphery of the lymphoid infiltrates. The basic feature is an intermingling of lymphocytes, histiocytes, and ‘nevus cells.’ Often the ‘nevus cells’ are atypical. I suppose the cytologic features in such cases might be dismissed as a response to the lymphoid infiltrates (i.e., a degenerative change) or even attributed to ‘ancient change’ (the evocation of images of cells too old to function normally). In the concept of near-neoplasia as based in the concept of MDM, the atypical changes are characterized as a marker for a minor step along the spectrum of neoplastic progressions. In turn, the lymphoid infiltrates are a defense mobilized to counter further progressions. Histologically, the lymphocytes and histiocytes among the altered ‘nevus cells’ induce lysis and coagulation of target cells (i.e., the ‘nevus cells’). Lytic defects are produced in the domain of the melanocytic cells. The process may be focal or diffuse and the factor determining the distribution of the infiltrates may have to do with the distribution of specific genetic derangements in the population of melanocytic cells. Some clones may by-pass the lymphocytotaxic phase and come to be committed to neoplastic progression, relatively independent of the effects of a cellular host immune response.

C5P2-1: Nests of cells of the variant vertical growth component are identified with blue arrows. A sheet of lymphocytes occupies most of the lower 1/2 of the field. Within the lymphoid infiltrate, there are individual, atypical (and epithelioid) ‘nevus cells’ and nests of similar cells (green arrows). In the nests, there is variation in nuclear size and staining of the ‘nevus cells.’ Some of the ‘nevus’ cells are pigmented (an uncommon feature at this level, if found in the setting of a common nevus). The patterns in the region of the lymphoid infiltrates are compatible with those of the dermal component of a common ‘halo nevus.’

C5P2-2: Light green arrows point to nests of atypical ‘nevus cells.’ These cells have enlarged, hyperchromatic nuclei with folds in the nuclear envelopes. These nuclear features are prototypic of the dermal dysplasia commonly manifested in halo nevi and halo nevus-like variants. The dark green arrows outline a zone of irregular cytolysis in the a domain of melanocytic cells in the dermis. In these areas, the ‘nevus cells’ show mild atypia and nuclear hyperchromatism. Red arrows point to acidophilic bodies; the structures are similar to colloid bodies but lack the central clear defect often seen in colloid bodies. They are not as pale as the pale acidophilic bodies, sometimes emphasized as a feature of Spitz nevus. They, in combination with the lytic phenomena, justify a comparison of the phenomena in halo nevus-like reaction with those of the cell-mediated changes of a lichenoid reaction (the difference being found in the character of the target cell [i.e., a melanocytic cell]).

C5P2-3: Lentiginous and junctional patterns are represented to the left of the center of the field. An island of squamous epithelium is represented in this area above and to the left of the center of the field. The cells of the lentiginous component are somewhat epithelioid; they are rounded and have pale cytoplasm. Some of the cells have migrated upward into the epithelium among keratinocytes. It should not be a source of pride to recognize this migration and then meekly classify the lesion as at least melanoma in situ; to do so would be a slight to all the other, and varied, features. A junctional nest is central and projects to the right. A defect in this nest contains lymphocytes and pigmented histiocytes. There is even a small colloid body. Like a lichenoid reaction, it is not the character and distribution of the lymphoid infiltrate which is the defining feature; it is the effects of the lymphoid infiltrate; the infiltrate is cytopathic and the most conspicuous effects are cytolysis of target cells (i.e., neoplastic melanocytes).

C5P2-4: There are angulated, small defects in the domain of this dermal (parafollicular) nest of melanocytic cells. Lymphocytes and pigmented histiocytes are sprinkled among the melanocytic cells in the defects; halo nevus-like phenomena are represented. Some of the melanocytic cells of the nest are larger than their neighbors, have more chromatic cytoplasm, and have enlarged, round, densely chromatic nuclei. The most striking example of these distinctive cells is in the defect just to the right and above the center of the field. Lymphocytes and histiocytes cluster in rosette patterns at the periphery of this cell. This cell might be cited as a marker for an early step-wise progression in the stage of neoplasia and as the emergence of a progenitor of a new clone of melanocytic cells; this cell is the harbinger of the near-neoplasia of the precursor of MDM of halo nevus-like type.

C5P2-5: To the right of the center of the field, a nest is composed of uniform, atypical cells; the general blandness of the cytologic features is a minimal deviation quality. The presence of nucleoli in many of the nuclei would mark the grade of dysplasia as moderate. Green arrows mark the margin of a large area of cytolysis with loose infiltrates of lymphocytes and pigmented histiocytes. A few clusters of melanocytic cells are preserved in the area of cytolysis.