Fig. P2-1 (extreme left corner of  field resented in P1-1): Although the pattern at this magnification might be characterized as having nevocytic qualities, there are deviations. Near the dermal-epidermal interface, fascicles of pale cells are loosely but regularly spaced in a widened, fibrotic papillary dermis (a nevoid quality). Condensed fibrous tissue outlines each fascicle in this area. Below this zone, small pale cells form smaller, more closely spaced fascicles. The blue nodule (blue arrow) near the right hand margin of this field is a cluster of lymphocytes in a nest of atypical melanocytes (halo nevus-like phenomena?).

There are variations, but the pattern basically is expansile. These qualities, if associated with both cytologic atypia and deviant patterns of aggregation (i.e., patterns in which cells are aggregated and patterns in which nests of cells are distributed), should evoke virtual images of a vertical growth component (the relevance of such images is another matter). The patterns do not correspond to those of a common nevus. Fascicular patterns are better represented near the dermal-epidermal interface. There are junctional components and this might be cited as evidence that the dermal component has evolved from a population of cells at the dermal-epidermal interface (a variation of so-called primary configuration).

Fig. P2-2: At higher magnification (area just to left of center of field in fig. P2-1), the patterns clearly are not those of a common nevus. The cells are pale and spindle shaped. In clusters, the cells provide an “epithelioid” quality. The cells form loosely spaced fascicles in a fibrotic, widened papillary dermis and are not associated with significant lymphoid infiltrates. In the lower portion of the field, the fascicles are smaller and more closely spaced. In the latter location, the cells also have less cytoplasm (i.e., variations in patterns in keeping with so-called maturation).

The continuity of nests of cells in  the epidermis with the dermal component would identify the overall pattern as having a “primary configuration,” once the dermal component has been identified as a vertical growth component. The loose spacing of the nests of spindle cells in the upper 1/2 of the field would be in keeping with variant vertical growth. This is also true of the pattern in the lower 1/2 of the field but here the fascicles are smaller and more closely spaced; they are not back to back (i.e., they do not satisfy criteria for typical vertical growth). The cytologic features are rather monotonous even at this magnification.

Fig. P2-3: At higher magnification, this area near the dermal-epidermal interface has fascicular qualities. The cells forming the fascicles are short spindle cells with pale cytoplasm. A multinucleated giant cell (nevocyte-like giant cell) is present to the left of the center of field. Melanophages are loosely clustered in the stroma. The stroma is densely  fibrotic.

At this magnification, some observers might be inclined to classify the lesion as a Spitz nevus or variant thereof. The multinucleated giant cell to the left of the center of the field might be offered in support of this interpretation. Actually, the giant cells are of a type seen in melanocytic neoplasms in spindle cell configurations and are especially common in lentiginous dysplasias and melanomas, such as the actinic variants (i.e., lentigo maligna and lentigo maligna melanoma).

The cytologic features are not those of a classic Spitz variant. To characterize the pattern as Spitz nevus-like would be a concession to spindle shaped melanocytes in a variety of clinical and neoplastic settings. The nuclear configurations and chromatin patterns are not Spitz nevus-like. The nuclear features might be characterized as relatively bland and this quality evokes images of a minimal deviation, spindle cell melanoma.

Fig. P2-5: At the top of the field, the transition from the loose fascicular patterns to the more cellular patterns is represented. Even in the more cellular areas, many of the small fascicles are separated from their neighbors by a thin band of condensed fibrous tissue. In the lower left-hand corner, the closely spaced, small fascicles form an aggregate which somewhat distorts the neighboring fibrous tissue; the lesion in this area has an expansile or nodular quality. There are spotty infiltrates of lymphocytes among the tumor cells to the left above the center of the field.

The fascicles and the cells forming the fascicles are smaller in this portion of the vertical growth component than in the more superficial portion of the field. This quality might lead an observer to propose that this small cell component is evidence of maturation; this selection of a parcel of virtual images (i.e., those defining maturation) might then lead the observer to a conclusion that the lesion is benign and a variant of a Spitz nevus. The aggregates of thin fascicles provide a solid, expansile quality,and there is some evidence of distortion of connective tissue at the margin of the nodule on the left. This pattern satisfies the requisites for the recognition of vertical growth with minimal cytologic deviation. In addition, the variations in patterns, when the superficial portion is compared to the deeper portion, might be cited as evidence that the process has evolved in neoplastic sequences, and that the small cells in the deeper portion are older and less advanced neoplastically than the more superficial portion. The patterns then become a marker for the accretive nature of neoplastic progressions evolving at the dermal-epidermal interface (see the WHITHERS 1,  2,  & 3 ).

Fig. P2-6: The nuclear features as seen in this field differ from those of classic Spitz nevus.The chromatin is rather densely distributed in most nuclei. Some nuclei show central clearing of chromatin with heavily stained nuclear membranes. Nucleoli are variable.The nests of cells are closely spaced at this deeper level (same level as seen in fig. P2-5) with poorly defined margins and scattered, thin collagen bundles among the nests (patterns take on some of qualities of typical vertical growth in this field).

Here, epithelioid cells, in small nests and as individuals, infiltrate the reticular dermis among collagen bundles. The cells have pale cytoplasm and rounded nuclei. There is some variation in nuclear sizes, outlines, degrees of chromatism. The cells resemble those commonly encountered in the vertical growth components of minimal deviation melanoma of halo nevus-like type or dermal type. The patterns are sufficiently deceptive to easily lead an observer to a diagnosis of “nevus” or perhaps “Spitz nevus.” On the other hand, these deceptive nevoid qualities might be cited as evidence in support of some type of minimal deviation or nevoid melanoma.

Fig. P2-7 (general area indicated by blue arrows in P2-1): The cells are somewhat epithelioid (in the sense that they are rounded and focally clustered in nests). They have pale cytoplasm and mostly rounded, somewhat irregular nuclei. Some of the nuclei show marginated chromatin and a central nucleolus. Nuclear membranes of some of the nuclei are thick and heavily stained. Some of the cells extend in nests and individually into the reticular dermis among preexisting collagen bundles. A vessel on the right shows mild, perivascular lymphoid infiltrates. Otherwise, markers for host immune response are not a significant feature.

Facility in the manipulation of virtual images would be required if an observer is to feel comfortable after assigning a neoplasm with these cytologic features to the category of a Spitz nevus. On the other hand, the cytologic features are reminiscent of patterns encountered in the vertical growth components of minimal deviation melanomas of the halo nevus-like type and the dermal type. The latter two variants are closely related and can be distinguished only in the presence of convincing markers for halo nevus-like phenomena.