|
EPITHELIOID MELANOCYTIC NEOPLASIA
Epithelioid melanocytic neoplasia of either spindle, or round cell type, if encountered in daily practice, is likely to be assigned to the category of Spitz nevus, whether the virtual images of the
appropriate parcel can be accurately matched with the real images of the lesion or not. From a different perspective, the category of epithelioid melanocytic neoplasia is diverse with classic Spitz nevus as one of
several variants. If deviations from the classic patterns are encountered when attempting to match virtual images with real images, then perhaps the respective lesion should be given recognition in categories other
than that of classic Spitz nevus. Much of the current controversy that has compromised the utility of the Spitz category can be traced directly to a willingness to bend and modify parcels of virtual images. If
molding and accommodations are required to fit virtual images of a selected parcel with deviant real images (in these attempts, it is even possible to distort real images!), then other parcels should be selected or
structured to fit the real images. In structuring new parcels, deviant features such as cytological atypia, pleomorphism, lack of maturation, premalignant melanocytic dysplasia-like patterns, and rather uniform
mitotic activity are to be considered. Since even classic Spitz nevus behaves in the fashion of a neoplasm rather than a hamartoma, it is best characterized as an epithelioid melanocytoma of Spitz type.
Lesions with deviant features that cannot be easily accommodated in the classic Spitz type category can be characterized as either dysplastic epithelioid melanocytoma or epithelioid minimal deviation melanoma, and
then qualified as to subtype depending on the combination of deviant features. Lesions in the dysplastic epithelioid melanocytoma category showing typical vertical growth patterns and cytological atypia are best
assigned to the MDM category. If the lesion is loosely fasciculated and atypical, then the possibility of minimal deviation melanoma in variant vertical growth patterns cannot be ruled out but a defense for such an
assignment would require a great willingness to impose “intensions” on not only virtual, but also the real, images.
To characterize the problem lesion as a dysplastic epithelioid melanocytoma and additionally qualify it as melanocytic neoplasia of indeterminate, or uncertain, malignant potential is a more honest appraisal of
what we know of the biologic potential of phenotypically ambiguous lesions lacking patterns of typical vertical growth.
For our problem case, the epithelioid character of most of the cells is apparent. Basic patterns of a common nevus (vertically oriented fascicles in a specialized stroma) are somewhat preserved and in addition,
some nests of pigmented, small (“common”) nevus cells are loosely spaced in the dermal component. Focally, halo nevus-like phenomena are represented. These are common features of halo nevus-like neoplasia. The
extensiveness of the epithelioid cell change might be cited as a feature favoring a minimal deviation melanoma but the rather uniform, bland cytological features and the ill-defined fascicular patterns of the
epithelioid component mollify the prognostic implications of the rather uniformly cellular patterns. I would favor classifying the lesion as a dysplastic epithelioid melanocytoma of halo nevus-like type and
would append the qualification, melanocytic neoplasia of indeterminate malignant potential. It is difficult to ignore the parcels of images that define MDM of halo nevus-like type in variant vertical growth but the
likelihood of metastasis from a lesion of this type is anecdotally remote.
In the problem lesion, junctional components are clearly defined but an area in which junctional nests appear to make a significant contribution to the dermal component is difficult to identify. The patterns in
the dermis provide evidence that the cytolytic changes (halo nevus-like phenomena) in the dermal nevus cell-like component are related to the emerging epithelioid cell component (i.e., the emergence of one is
determined by the presence of the other). In some areas, the epithelioid cell component is arranged in ensheathing patterns about nests and fascicles of pigmented, small nevus cells showing cytolytic
phenomena. The epithelioid cells apparently have made the neoplastic step that leads from nevus cell-like populations and halo nevus-like phenomena to epithelioid cell populations, less closely associated with halo
nevus-like phenomena.
A general category of epithelioid cell melanocytoma (in spindle and round cell patterns) would offer great utility, facilitating the manipulation of virtual and real images and avoiding compromise of the classic
Spitz nevus category.
Dysplastic Melanocytomas
and Related Minimal Deviation Melanomas.
(with emphasis on epithelioid cell variants)
I. dysplastic melanocytoma of halo nevus-like type
A. dysplastic melanocytoma, junctional type (atypical halo nevus-like variant): patterns of premalignant melanocytic dysplasia at dermal-epidermal interface in combination with halo
nevus-like phenomena; usually, but not invariably, there is a component in the upper portion of the dermis showing a common nevus-like remnant; occasionally represented by plump spindle cells forming fascicles at
the dermal-epidermal interface (Spitz nevus-like cytological guise)
B. dysplastic epithelioid melanocytoma of dermal type (epithelioid near-neoplasia of halo nevus-like type): emergence of epithelioid, round cells in dermal nests among common nevus
cells (small cells that morphologically resemble common nevus cells but often are pigmented and show nuclear hyperchromatism; variable degree of round cell transformation from spotty individual cells to almost
complete replacement of common nevus cells by epithelioid round cells; preservation of fascicular and nesting patterns in dermal component (nests spaced in papillary dermis in patterns that also could be
characterized as variant vertical growth-like patterns
II. Spitz nevus-like dysplastic epithelioid melanocytoma: variant or migrant vertical growth-like patterns with implication that there is some degree of atypia and that there are also markers for host immune
response
A. borderline Spitz nevus-like dysplastic melanocytoma: a thin lesion [less than 1 mm in vertical dimensions] with patterns of premalignant melanocytic dysplasia in combination with
Spitz nevus-like cytological features; includes provision for thin variant or migrant vertical growth-like patterns
B. immature Spitz nevus-like dysplastic melanocytoma: most of features of classic Spitz melanocytoma but maturation not a significant feature and cytologic atypia variable in degree
C. pleomorphic Spitz nevus-like dysplastic melanocytoma: most of features of classic Spitz melanocytoma but with marked cytologic atypia and pleomorphism, and usually lacking in
maturation
D. dermal dysplastic epithelioid melanocytoma: lacking significant junctional patterns; usually preponderantly a round cell variant of reticular dermis; variable degree of sclerosis;
variable degree of atypia; often characterized as dermal variant of “Spitz nevus”
III. dysplastic melanocytoma of pigmented spindle cell type (typical and atypical pigmented spindle cell nevus of Reed); dermal component common in patterns that are typical vertical growth-like but generally show
prominent maturation
IV. dysplastic melanocytoma, ambiguous phenotype
V. dysplastic melanocytoma, cellular blue nevus type (atypical cellular blue nevus)
V. MDM (halo nevus-like variants): typical, or typical as well as migrant, vertical growth-like patterns; a nodular lesion with areas in which fascicles and nests of cells are closely spaced [cytologic atypia,
including immaturity and pleomorphism as defined above]
A. accretive variants: junctional components have apparently contributed the cells forming a dermal tumor: MDM of halo nevus-like type, accretive growth of nests of cells at the
dermal-epidermal interface; so-called primary configuration; Breslow’s criteria probably have some application in predicting likelihood of metastasis
B. dermal (interstitial) variants: progression from patterns of near-neoplasia of halo nevus-like type, dermal variant to patterns of typical, or typical as well as migrant vertical
growth; a nodular component composed of epithelioid, round cells; emergence of vertical growth primarily from dermal population of cells; non-primary configuration with interstitial growth; cannot be evaluated as to
likelihood of metastasis by Breslow’s criteria; apparently an extremely low potential for metastasis
IV. MDM (Spitz nevus-like variants): typical, or typical as well as migrant, vertical growth-like patterns; a nodular lesion with closely spaced fascicles and nests of plump cells usually of spindle cell type;
varying degrees of atypia, immaturity, and pleomorphism; mitoses, often at all levels; some correlation between size and likelihood of metastasis but cannot be evaluated with confidence by Breslow’s criteria
V. MDM (dermal variant, round cell type, ambiguous phenotype): dermal nodule (MDM) with typical vertical growth-like patterns; usually associated with remnant of common nevus in adjacent dermis; remnant is
often of small congenital nevus type; round cells show cytologic atypia with variation in nuclear size, staining, and outlines; nesting patterns usually preserved in nodule and some of nests often resemble common,
small nevus cells; specialized stroma supporting cells of nodule; occasionally the nodule shows variant vertical growth-like patterns with loose spacing of nests; halo nevus phenomena variably represented in nodule
but not in nevic remnant in adjacent dermis; distinctions between dermal variant of MDM and halo nevus-like variant of MDM, dermal type, are difficult to define; one may be the other in absence of markers for halo
nevus-like phenomena (i.e., a distinctive dermal neoplasm, sometimes but not always associated with halo nevus-like phenomena)
VI: MDM (congenital nevus variant; atypical nodular hyperplasia)
VII: MDM (nevoid variant): variant vertical growth patterns; maturation a common feature; basic patterns resemble those of common nevus; lesion not readily classifiable in categories relevant to variant nevi
VIII: MDM: ambiguous phenotype, spindle or round cells, but not readily assigned to usual variant categories
NOTE: category of atypical or dysplastic melanocytoma generally restricted to thin lesions less than 1 mm in vertical dimensions. Practically, all dysplastic nevi of common type would be characterized as
dysplastic melanocytomas of common type; they are all new growths rather than hamartomas and may or may not be associated with a remnant of a common nevus (hamartoma).
Basic phenomena of near-neoplasia of halo nevus-like type are represented in P5-1.
|
