|
From a histologic examination of this lesion, virtual images will be generated, but the amalgam will not be representative of a single classic parcel. The parcels likely will include those for the interpretation
of “nevoid melanoma,” those relevant to Spitz nevus-like variants, those relevant to halo nevus-like variants, and even a poorly defined parcel for the interpretation of lesions of ambiguous phenotype. The patterns
in this lesion provide an opportunity to explore the concepts of variant nevi, minimal deviation melanomas, and even common melanomas (they offer a direct contradiction of the expression: “one melanoma, biologically
and histologically”).
In the problem lesion, the expressions of phenotype as judged by cytologic features are ambiguous. The junctional component, as well as some of the dermal patterns, can be characterized as Spitz nevus-like (in
selecting this parcel, molding of images and accommodations for deviance among real and virtual images are required) (P2-3, P3-5, P4-2). Spindle cells form fascicles at the dermal-epidermal interface
(somewhat Spitz nevus-like). Within the fascicles, the cells are loosely attached to their neighbors (Spitz nevus-like). The spindle cells are pigmented in the junctional component, but this quality does not totally
negate the parcels of Spitz nevus-like images. The cells in the junctional component are spindle shaped, and those of the dermal component are epithelioid; for pathologists whose pathologic interpretations are
strongly influenced by words (i.e., spindle and epithelioid cell melanocytic neoplasm = Spitz nevus) this combination of features provides access to the parcels of Spitz nevus-like images.
Patterns in the dermal component find accommodations in parcels which have relevance for the interpretation of halo nevus-like lesions (again some molding and accommodations are required) (P1-1a-c, P2-4, P3-1-3, P3-5, P4-1-4). In one area near a margin of the lesion, a band-like infiltrate of lymphoid
cells fills the deep portion of a widened papillary dermis and extends to the interface between the papillary dermis and the reticular dermis (P1-1a&b, P1-2a&b). Fascicles of spindle cells extend into the band-like infiltrate of lymphoid cells. Small nevus cell-like components show both the nuclear
features and the pigmentation commonly encountered in the dermal component of classic halo nevus (P3-4). In addition, the epithelioid cells can be
accommodated in parcels with relevance for the interpretation of halo nevus-like lesions showing epithelioid cell change in the dermal component. It has been proposed that this change might be characterized as
NEAR-NEOPLASIA OF HALO NEVUS-LIKE TYPE, DERMAL VARIANT. In this characterization, the presence of a “typical” vertical growth-like component would be a discordant
feature.
The area showing a preponderance of epithelioid cells in the dermal component (P1-3, P4-3) introduces problems in regard to what is necessary for the recognition of vertical growth components, and raises questions as to the significance
of those patterns in regard to them representing an obligate marker for melanoma. The close spacing of nests of cells in the epithelioid component results in a rather “solid” pattern in which the distinctions
between variant and typical vertical growth are difficult to define (P1-3). The problems in the interpretation of this lesion seem to favor halo nevus-like
phenomena but there are problems in defining on the one hand the boundaries between distorted nevoid patterns and variant vertical growth, and on the other those between variant and typical vertical growth;
depending on whims, the lesion might be characterized as a dysplastic melanocytoma (a new growth but not clearly a melanoma) or as a MDM (a new growth with melanomatous patterns).
If emphasis is placed primarily on the many ambiguities encountered in the interpretation of this lesion, the designation, NEVOID MELANOMA, becomes a consideration. In this approach, there is no need to anguish over the distinctions between Spitz nevus-like category and halo nevus-like category. The epithelioid
cells become an oddity rather than a morphologic contention. Would such an approach be sufficient to then justify an evaluation of the lesion by Breslow’s criteria with the relevant implications regarding surgical
treatment and prognosis? Clearly some “nevoid” melanomas are cytologically high grade and biologically aggressive. Currently, the diagnosis of “nevoid” melanoma does not carry with it cautions as to the biologic potential of the respective lesion. Many of the reported “nevoid” melanomas have been categorized as such in retrospect; the lesions have initially been misdiagnosed as benign and only with the appearance of recurrence or metastasis on follow-up has the interpretation been altered and the label melanoma been appended; in retrospect, the pathologist has interpreted the patterns as those of a melanoma of “nevoid” type. This characterization often is offered as a salve for misdiagnosis; nature in her patterns was deceitful. In regard to the problem case, nevoid qualities are evident in most of the pictorials (P1-1a, P2-3-5, P4-3).
Clearly, there are problems with simply dismissing the lesion as some type of “nevus.” In addition, if we attempt to make distinctions between “nevus” and
“nevoid” melanoma, problems arise. Critics of MDM seem to be entirely comfortable with the concept of “nevoid” melanoma. They seem to be undisturbed by the lack of discrimination in the diagnosis; there is no
provision for distinguishing between high grade and low grade melanomas; patterns that might suggest a relationship between “nevoid” melanoma and a benign precursor are simply ignored. If someone eventually makes an
effort to relate deviant patterns in “nevoid” melanomas to specific type of variant “nevi,” he probably will additionally find that he has validated the concept of MDM.
|
