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Juvenile Melanoma [Spitz Melanocytoma: intermediate (borderline) neoplasia]:
The current terminology for the Spitz category includes Spitz nevus, “atypical Spitz nevus” of Barnhill (as opposed to “atypical Spitz nevus” of Reed - the latter characterization is based in part on the patterns of a premalignant dysplasia, sometimes in combination with a thin [less than 1 mm in vertical dimensions] dermal component), “Spitzoid” melanoma, metastasizing Spitz nevus, Spitz nevus-like melanoma, and MDM of Spitz nevus-like type.
Herein, the designation, juvenile melanoma, is offered as an alternative. A new system of logic replaces the logic which Spitz promoted in her definition of juvenile melanoma. In this alternate approach, in which classical Spitz “nevus” is transferred from the nevoid category to the neoplastic category, the broad category is representative of intermediate neoplasia. The category is divisible into at least two types, a classical type and an atypical type. Classical Spitz “nevus” (there is some question as to the histologic features of the classical type, if the illustrations of the early reports are relied upon as the reference) loses its identity in this new approach; it comes to be accepted as a neoplasm rather than a nevus. In the logic related to this new set of truth functions and values, classical Spitz type has the histologic features of classical Spitz “nevus,” but the logic does not exclude limited nodal metastases; in this new logic, documentation of nodal metastases, particularly those discovered by sentinel node biopsy, would not then serve to equate the primary lesion with an outright common (the “one”) melanoma. I suspect that if we were to perform sentinel node biopsies on all classical Spitz “nevi,” some will be found to be associated with nodal metastases. The structure of the logic in this approach would accept the possibility that nodal metastases may occur in association with classical Spitz “nevus,” but in most instances the nodal deposit would remain clinically inapparent. I am too old to think that this logic might be accepted; I am too old to care one way or the other. I am old enough to doubt that the current dilemmas in regard to the nature of lesions in the Spitz category can be resolved by reliance on the current divisions, and on current terminology.
Currently, our logic has resulted in: a muddled Truth Table; confused pathologists and clinicians; and distraught patients and their families. I am also old enough to realize, that once a nodal deposit is identified in the setting of a Spitz lesion, an oncologist will not have the statistical support to recommend watchful waiting, and the patient, or the parents of a patient will have to accept treatment which relates to the protocols for the management of a common melanoma. It seems unlikely that clinical studies will ever define the basic nature of lesions in the Spitz category (perhaps this is true of all MDM with the exception of the pigmented spindle cell variants).
An example with most of the features of a classical Sitz “nevus” serves to illustrate some of the problems. In this example, the lesion has the configuration of an inverted wedge. Fascicles of spindle cells centrally form an expansile nodule; in this nodule, the fascicles are closely aggregated; the patterns take on the qualities of a typical vertical growth component (figs. c22t3P1-8). The fascicles are broad at the dermal-epidermal interface; they are not as broad in the deeper portion of the dermis beyond the nodule. A less organized component is present in the dermis adjacent to the nodule; it is closer in pattern to classical “Spitz nevus” than is the expansile nodule. In the nodule, the cells are monotonous and uniform. There is a low mitotic rate. The cells of the nodule generally are smaller than those of classical “Spitz nevus.” In the deeper portion of the dermis, the fascicles infiltrate the dermis among collagen bundles. Maturation, as evaluated by size of individual cells, is not a prominent feature. The lentiginous and junctional components extend in the epidermis away from the dermal nodule; in addition, there is upward migration of nests of cells, and individual tumor cells into the epidermis. A few Kamino bodies are present in some of the junctional nests. In the nodule, stroma is scanty; it is condensed among the closely spaced fascicles. Near the epidermis, nuclei of the tumor cells are plump; they show marginated chromatin, and a prominent central nucleolus. Focally, some of the patterns have a nodular quality; the nodular components have the qualities of typical and migrant vertical growth (c23t3P1-6); there is a mild degree of nuclear pleomorphism. This is a recent lesion; there is no follow-up.
In a second example (contributed by Ron Barr, MD), many typical “Spitz” qualities are represented. The lesions is symmetrical with limited spread in the epidermis away from the dermal component. The epidermis is hyperplastic. The papillary dermis is widened; it is hyalinized and focally edematous. Vessels of the papillary dermis are ectatic. Fascicles of neoplastic cells rain down from the epidermis into the widened papillary dermis; they extend into the reticular dermis among collagen bundles. There is maturation at the advancing margin in the reticular dermis. The most deviant features are manifested at the cytologic level; there is nuclear atypism, and pleomorphism (figs. c24t3P1-6, and c25t3P1). The atypical cells vary in size. Some are large. Some are pigmented. The cytologic features of some of the smaller atypical cells are reminiscent of those seen in classical examples of SSM. Some of the atypical nuclei show dense chromatin patterns. Atypical cells are prominent in the lentiginous component, and variably represented in the fascicular components in the dermis. Infiltrates of inflammatory cells are mild. A sentinel lymph node was reported as positive.
Try to structure a “truth table” for either of these two lesions. The history of a positive lymph node colors the interpretation of the second lesion. To accommodate the information that the lesion has metastasized, efforts would be expended to find histologic features that can be correlated with a potential for metastases. The observer would assume that histologic clues of a malignancy are represented; he would assume that he is on his way to an understanding of a Spitz “nevus” gone bad.
In the first case, the expansile nodule might be interpreted as a typical vertical growth component; the lesion then might be assigned to the MDM category (I realize that the likelihood for this sequence would exist mostly for me, and a few others, rather than for most pathologists). On the other hand, atypia is minimal, and mitotic activity is not a prominent feature (it is not a prominent feature of either lesion). If, for either lesion, an assignment to either a benign or malignant category is the only option, the observer in his search for clues might do as well by simply tossing a coin.
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