d. Presentation histopathologic of pigmented epithelioid melanocytoma

 
In order to ensure that the observations of the authors are transmitted exactly, their own words will be quoted just as they wrote them:
 
"At scanning magnification, pigmented epithelioid melanocytomas were heavily pigmented dermal melanocytic tumors with infiltrative borders. Eleven lesions extended into subcutaneous tissue along periadnexal connective tissue of hair follicles, pilar muscle, eccrine coils, or neurovascular bundles. At the periphery, tumor cells permeated between preexisting collagen fibers with no or minimal Desmoplastic stroma response. Some tumors abutted the epidermis, occasionally inducing epidermal hyperplasia; others were separated from the epidermis by a Grenz zone of uninvolved dermis. Seven tumors were ulcerated. A minor junctional component was present in 10 cases. In eight cases, all associated with epidermal hyperplasia, the junctional component consisted of dendritic melanocytes. In two cases, the junctional component resembled the usual junctional nevus and was part of a combined nevus. Three additional cases of combined nevus with a dermal component of a common nevus were present. In one case, the associated nevus had features of congenital onset.
 
All tumors were composed of a mixture of epithelioid and spindled melanocytes with heavy pigmentation. The epithelioid cells occupied the central portions of the lesions and consisted of two distinct cell populations with rare intermediate forms. Most abundant were medium-sized round to polygonal cells with heavily pigmented cytoplasm, which formed cohesive sheets or nests of closely packed uniform cells. They contained round to oval vesicular nuclei with variably prominent nucleoli. The second epithelioid cell type was less numerous and sometimes difficult to find. These cells were large with abundant cytoplasm. They often lacked pigmentation or had dot-like melanin granules at the periphery of the cell forming a concentric rim around a halo of nonpigmented cytoplasm. The nuclei were large, vesicular with round or irregular contours and prominent eosinophilic or amphophilic nucleoli. Occasional cells contained multiple nuclei. The number of atypical epithelioid cells varied from few to numerous.
 
Epithelioid cells were intermixed with a variable number of spindled cells that were more numerous toward the periphery of the lesions. The spindled cells were present singly or formed small groups penetrating among the surrounding stromal collagen bundles. Spindled cells have the same nuclear features as those of epithelioid cells. Rarely, they have smaller darkly staining nuclei, similar to those of common blue nevus. Cytoplasm was abundant and heavily pigmented with occasional long dendritic extensions. Melanin bleached sections were helpful in evaluation of nuclear features.
 
Mitotic activity was infrequent and ranged from 0 to 3 mitoses/mm2. There was an area of tumor necrosis in one case adjacent to solid expansive nests of spindled cells with reduced cytoplasmic pigmentation and severe cytologic atypia, reminiscent of spindle cell melanoma. The sentinel lymph node metastasis in this case showed pigmented epithelioid melanocytoma, not the spindle cell melanoma-like component.
 
Melanophages, constituting less than 10% of the cells in the tumors, had coarser and darker cytoplasm in comparison to melanocytes and more oval and regular nuclei that often contained multiple small nucleoli.
 
Non-brisk lymphocytic infiltrate was present focally in seven cases. In two, the infiltrate was focally brisk. It was more accentuated at the periphery of the lesions and in the areas containing melanophages. Rare neutrophils were also encountered in melanophages-rich areas."
 
On the basis of the changes histopathologic just detailed by Zembowicz, Carney, and Mihm, a reader cannot come to a determination about whether the neoplasm termed by them pigmented epithelioid melanocytoma is benign or malignant. For example, nowhere is there mention of two attributes crucial for deciding that issue, namely, symmetry versus asymmetry and maturation with descent progressive versus no maturation with descent progressive. The observation of "infiltrative borders" is meant to suggest that the lesions were circumscribed poorly, but that also is a feature of conditions "benign" as disparate as so-called common blue nevus and dermatofibroma, and, moreover, all the other findings recorded by the authors are consonant with benignancy, among those being extension of neoplastic cells "along periadnexal connective tissue of hair follicles, pilar muscle, eccrine coils, or neurovascular bundles" (i.e., adnexocentricity in the absence of destruction of structures adnexal), nuclei being "large" (but not pleomorphic), and mitotic activity "infrequent" (with no mention of any mitotic features being abnormal).
 
In short, the coworkers do not present data that compel to a conclusion that on grounds histopathologic pigmented epithelioid melanocytoma is malignant. In fact, they, themselves, were completely puzzled by these lesions, to the point that they were unable to decide whether they were dealing with neoplasms benign or malignant. It is apparent that this incapability was the result of failure to apply criteria solid, for example symmetry vs asymmetry, maturation with descent in the dermis vs no maturation, etc., to the assessment.