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Introduction (MDM):
In Chapter 4 (pictorial 1), the overall morphology of the lesion on the original skin specimen is manifested at increasing levels of magnification. At low magnification, the lesion is plaque-like at the surface of
the skin. It has thin vertical dimensions and has a rather sharply defined lower margin (C4P1-1&2). There are lentiginous and junctional
patterns at the dermal-epidermal interface. The atypical cells also form nests and fascicles in a widened papillary dermis. The wide spacing of the nests in the widened papillary dermis might be characterized as a
variant vertical growth pattern (C4P1-3&4); in this usage, we would not necessarily imply that this is a melanoma. We would be giving
recognition to patterns at low magnification and, at the same time, employing cautions which would circumvent a presumptuous diagnosis at too early a stage in the process of microscopic examination (i.e., pattern
analysis at low magnification); there are other lenses and other criteria to be met. We might, however, take the patterns we have developed up to this stage of the examination and characterize the lesion as having a
primary configuration (see navigation guides to the WHITHERS in the left margin), again without necessarily committing to a diagnosis of melanoma. Red arrows define an ill-defined boundary between two populations of cells in the dermis (C4P1-1, 2&3). At the interface between the papillary dermis and the reticular dermis there is a band-like infiltrate of lymphocytes and
above this level, there is a band-like infiltrate of small nevus-like cells (C4P1-5). The latter may be a marker for a preexisting nevus but
might also represent an early generation of neoplastic cells that, in their minimal genetic deviations, only resemble common nevus cells. Certainly, these cells in areas are slightly larger than common nevus cells
and, peculiarly, have clear cytoplasm. These cells deviate slightly from common nevus cells. There is a thin zone of fibrous tissue above this population of nevus-like cells. Above this boundary are nests and
fascicles of atypical cells which deviate more significantly from common nevus cells. In areas, these cells form small rounded nests that are regularly spaced in the altered papillary dermis; in other areas, these
cells form fascicles. With the criteria in the concept of MDM, the patterns are compatible with those of a variant vertical growth component. For the patterns identified at low magnification, we have, at a
higher magnification, provided supporting evidence that some of the patterns can be accommodated in the concept of vertical growth (and more specifically, variant vertical growth). With an additional stipulation
that the neoplastic cells of the vertical growth component are minimally atypical (a seemingly accurate characterization, but of little significance for those with no appreciation for degrees of atypia), a note of
caution seems advisable, if a diagnosis of melanoma is a consideration. Such a note of caution is inherent in the an assignment of a problematic lesion to the category of MDM.
The initial photomicrographs as presented in Pictorial 1 also document the thinness of the lesion in a vertical orientation. The lesion measures less than 1mm in vertical dimensions; by current criteria, as
embodied in the concept of minimal deviation melanoma, this lesion, if judged to be a melanoma, would fall in Breslow’s good prognosis category; by the criteria of the concept of minimal deviation melanoma, it
would, on the basis of its limited vertical dimensions, qualify as a borderline melanocytic neoplasm of indeterminate malignant potential. The likelihood of metastasis (if the lesion is truly a melanoma) would
appear to be too remote to be cited as an indication for a wide excision of the area, and/or a prophylactic lymph node dissection (assuming that an observer would even classify the lesion as melanoma).
In some areas away from the better developed dermal patterns, as described above, the nests of cells in the dermis are fewer in number and less regularly spaced. In these areas, it would be difficult to defend a
characterization of the patterns as variant vertical growth. In some of the nests near the dermal-epidermal interface in these same areas, some of the cells are large and have irregular, hyperchromatic nuclei;
chromatin is rather smudgy (C5P2-2). Other cells show similar chromatin patterns but the nuclei are not as large. In most areas
of the dermal component above the nests of common nevus-like cells, the cytologic features are uniform. The nuclei are fairly uniform in size and less than ‘large cell’ in type. Nuclear membranes are irregular and
chromatin patterns are open. The cytologic features in these areas are in keeping with changes found in the dermal component of many minimal deviation melanomas. In areas showing scattered large atypical cells, the
dermal patterns, even in the absence of lymphoid infiltrates, might be characterized as a halo nevus-like quality. These cytologic features are of a type seen in dermal cells in the setting of some halo nevi and are
also common in atypical halo nevi. In support of this comparison, the band-like infiltrate of lymphocytes at the interface between the papillary dermis and the reticular dermis might be cited as halo nevus-like
phenomena. Even more in support of this proposal would be the scattered foci in which lymphocytes and atypical melanocytes intermingle in lytic defects in the dermal component (C5P2-1-5). These patterns, in toto, invite the introduction of a parcel of halo nevus-like virtual images.
There is some evidence of upper migration of cells into the overlying epidermis focally on some of the sections (C6P3-4). On this finding alone, some
observers would have diagnosed the lesion as melanoma, and most of these proponents of a simplistic approach to the diagnosis of melanoma would also have assigned the lesion to the category of SSM.
Mitoses are not a feature of the epidermal or dermal components. Large nuclei with marginated chromatin are not a feature. In most practical terms, there would be utility in the recognition of large cell variants
of melanoma as opposed to the small or intermediate character of nuclei in many variant lesions. In this approach, SSM could also be characterized as a large cell variant of melanoma. If it had been so characterized
in the beginning, there would be less of a tendency to also assign less than large cell lesions to the category of SSM. We would not be so compelled to place all sorts of deviant lesions in one of the four major
categories.
Some of the patterns in the dermal component are characterized by the presence of large, ‘epithelioid’ cells. This attribute, if seized upon by certain cliques, would justify a categorization of the lesion as a
Spitz nevus or a variant thereof. The expansion of criteria for the inclusion of problematic lesions in the Spitz nevus category has reduced the category to the status of ‘junk-yard.’
In Chapter 6 (pictorial 3: C6P3-1-4), the patterns are those of variant vertical growth. Nests and fascicles of cells are loosely but regularly spaced
in a portion of a widened papillary dermis; they are arranged in tumorous patterns. In addition, the minimally deviant cytologic features of the cells in the vertical growth component would be in keeping with a
minimally deviant variant; some, or many, observers might find difficulties in attempting to accommodate these patterns in their common parcels of virtual images for the interpretation of common melanomas.
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