Pictorials

Fig. 1(right): The patterns include a lentiginous and junctional component at the dermal-epidermalinterface, and a small nodular component in which small nests of atypical melanocytic cells are loosely spaced in a lymphoid infiltrate. The neighboring papillary dermis is widened and contains spotty perivascular infiltrates of lymphocytes. The degree of dysplasia at the dermal-epidermal interface is moderately severe. The small nodule is representative of halo nevus-like phenomena. The cells of the small scattered nests are atypical. They resemble those of dermal halo nevus-like phenomena (i.e., they may well represent a change in the dermal component of a preexisting nevus). The reader should note that the patterns at the dermal-epidermal interface are of a type which some observers, having appreciation for neither atypia nor "host immune response," characterize eponymically as a "nevus."

Fig. 2 (left): The patterns at the dermal-epidermal interface are those of lentiginous and compound melanocytic dysplasia. Both moderately severe dysplasia at the dermal-epidermal interface, and a dermal remnant of a "nevus" (area outlined by blue arrows) in which the "nevus" cells are atypical (i.e., variability in nuclear size and nuclear hyperchromatism in the dermal component) are represented. Nuclear changes of the type seen in the dermis are common in the dermal component of halo nevus and related variants. Similar atypical nevus-like cells intermingle among lymphocytes in the adjacent dermis.On the basis of the nuclear changes in both the epidermal and the dermal components, the patterns are interpreted as halo nevus-like. The combination of a pattern of premalignant dysplasia, and a dermal halo nevus-like component qualify the lesion as an "atypical halo nevus ."

Fig. 3 (right): This pattern is fairly typical of that seen in the dermal component of a halo nevus. The nests of nevus cells are small and irregular in outline (blue arrows). Some are associated with lytic defects. The cells of the nests (blue arrows) have dense chromatin patterns and show variations in nuclear size and staining. Similar cells with plump, round, hyperchromatic nuclei are individually isolated in the loose, inflamed fibrous matrix (red arrows). The cytologic features are characteristic of halo nevus phenomena. The lytic defects in the nests are also a halo nevus-like feature. The lytic defects in association with cell-rich infiltrates of lymphocytes impart a "lichenoid" quality to the histologic patterns. The changes are in keeping with the cytolytic phase of the halo nevus-like reaction.

Fig. 4 ( left): At higher magnification, nuclear chromatin of the "nevus cells" is dense and the nuclei of these cells vary in size and outline. The loose, hypocellular matrix above the center of the field provides a marker for the cytolytic effects of a modified, "lichenoid" reaction in which the target cell is of melanocytic origin.

   Fig. 5 (right): It would be tempting to dismiss this pattern as representing nothing more than focal regression, as commonly encountered in the setting of the common premalignant dysplasias. On the other hand, the pattern could also be cited as a marker for the regressive changes associated with halo nevus-like phenomena. Band-like infiltrates of lymphocytes are represented focally. Melanoderma is a prominent feature. This pattern tempers the significance of any other cellular patterns that, despite cellularity, would fail to satisfy criteria for the recognition of a vertical growth component; the interpretation must be qualified as conservative on the basis of this focus of regression.

Fig. 6 (left): In this area near the dermal-epidermal interface, two lymphomelanocytic foci are outlined by red arrows. In these foci, plump, acidophilic ("epithelioid") cells are loosely spaced. The irregular defects of the nests contain lymphocytes and histiocytes. The epithelioid cells are rounded and have plump, rounded nuclei. They serve as a marker for the emergence of  "near-neoplasia" in the setting of halo nevus-like phenomena. A portion of a collection of similar cells with fewer interspersed lymphoid cells is represented to the right and superiorly (area outlined by blue arrows).

Fig. 7 (right): In this locus, the distinctive eithelioid cells of the dermal variant of near-neoplasia of halo nevus-like type are plentiful. Green arrows outline a lytic defect (a "lichenoid" quality). Yellow arrows outline a lymphomelanocytic island (a marker for near-neoplasia of halo nevus-like type). Blue arrows identify individual epithelioid cells. One to the right of the field is partially outlined by lymphocytes in an ill-defined rosette-like pattern.

Fig. 8 (left): The patterns of dysplasia are evident at the dermal-epidermal interface (blue arrows). To the left in the widened papillary dermis, small nest of cells and individual cells are loosely spaced. These are not typical nevus-like patterns. Lymphoid infiltrates are not prominent in the widened papillary dermis to the left of the center of the field.

Fig. 9 (right): At higher magnification, the patterns are nevoid but are not acceptable as those of a common nevus. This pattern may be an example of dermal dysplasia ab inflammation as seen in some patients with multiple lesions, in whom some of the lesions are classic halo nevi and some are dermal dysplasias that are more or less free of inflammation. The cytologic features would be compatible with those of halo nevus but lymphoid infiltrates are not a feature in this area

. Fig. 10 (left): A small nodule in the dermis is composed superiorly of thin, tortuous fascicles of uniform, small spindle cells. This component qualifies as a small, typical vertical growth component and the size of the nodule as well as the cytologic features of the spindle cells would qualify the patterns as those of a minimal deviation melanoma. The patterns of the preceding figures, in combination with the pattern in this figure, would qualify the lesion as a halo nevus-like variant. The nests of small dark cells outlined by blue arrows are acceptable by usual criteria as a remnant of a preexisting nevus but with closer attention to detail, the dense chromatin patterns might also be acceptable as a marker for a dermal melanocytic dysplasia of halo nevus-like type (dermal dysplasia ab inflammation). With the introduction of this figure into our sequence, vertical growth has been introduced as a variable in the complex of halo nevus-like phenomena.

Fig. 11 (right): Fascicles and nests of pale, uniform, but atypical, spindle cells form a plaque at the dermal-epidermal interface. The close spacing of the nests would qualify as typical vertical growth-like pattern. Beneath the plaque to the right, the band-like lymphoid infiltrates contribute halo nevus-like qualities. Beneath the plaque to the left, the laminated fibrous tissue provides a marker for the effects of regressive phenomena. The vertical growth component is larger and more atypical than the portion of the same component which is illustrated in fig. 10. The lesion qualifies as minimal deviation melanoma of halo nevus-like type and additionally qualifies as a spindle cell variant. Perhaps some observers would prefer to classify the lesion in the Spitz nevus category, a category is easily prostituted.

Fig. 12 (left): The right hand portion of fig.11 is seen at higher magnification. A portion of the vertical growth component is represented near the dermal-epidermal interface. Even at this magnification, the bland cytologic features of the spindle cells forming the vertical growth component are evident. Blue arrows mark the interface between the vertical growth component above and the halo nevus-like remnant below. To the right at the tips of the blue arrows, lymphomelanocytic islands of the type seen in fig. 6 can be identified by the looseness of the epithelioid cells in the nests. In these islands, lymphoid cells and epithelioid cells intermingle.