As if the matter of "animal-type melanoma" were not confounding enough, bewilderment incalculable was added to the subject by Zembowicz, Carney, and Mihm in the January issue of the American Journal of Pathology for 2004 [3] in an article titled by them, "Pigmented epithelioid melanocytomas: a low-grade melanocytic tumor with metastatic potential indistinguishable from animal-type melanoma and epithelioid blue nevus." In order to convey precisely the essence of the piece by Zembowicz, Carney and Mihm, the abstract of it will now be recorded just as they wrote it: "In the course of a study of borderline melanocytic tumors, we observed a distinctive group of lesions characterized by features very similar to those previously described in the literature as 'animal-type melanoma' and epithelioid blue nevus of Carney complex. We have designated these lesions as pigmented epithelioid melanocytomas (pigmented epithelioid melanocytoma). Herein, we present a clinical-pathologic analysis of 41 consecutive pigmented epithelioid melanocytoma from 40 patients and compare them with 11 epithelioid blue nevi from patients with Carney complex. pigmented epithelioid melanocytoma occurred in both sexes of different ethnic backgrounds, including white, Hispanic, black Asian, and Persian. The median age of occurrence was 27 years (range 0.6–78 years). Tumors had wide distribution with extremities being the most common site. The tumors were formed by deep dermal (mean Breslow's thickness 3.3 mm) proliferation of heavily pigmented epithelioid and/or spindled melanocytes. Five lesions were part of combined nevus. Ulceration was present in 7 cases. Tumor necrosis was present in 1 case. Regional lymph nodes were sampled in 24 cases (59%). In 11 cases, lymph nodes contained metastases (46%). Liver metastases occurred in 1 case. None of the patients died of disease. Clinical follow-up of more than a year (mean 232 months, range up to 76 months) was available in 27 cases (67%). We found no histologic criteria separating metastasizing and nonmetastasizing pigmented epithelioid melanocytoma. Ulceration was the only feature more common in pigmented epithelioid melanocytoma than epithelioid blue nevi of Carney complex. Otherwise, they were histologically indistinguishable. Our data show that pigmented epithelioid melanocytoma is a unique low-grade variant of melanoma with frequent lymph node metastases but indolent clinical course. We suggest that pigmented epithelioid melanocytoma be considered as a provisional histologic entity encompassing both animal-type melanoma and epithelioid blue nevus."

In brief, the authors assert that what they designate "pigmented epithelioid melanocytoma" is a melanoma ("a unique low-grade variant of one"), both animal-type melanoma and epithelioid blue nevus themselves being examples of pigmented epithelioid melanocytoma (that term for them "encompassing both animal-type melanoma and epithelioid blue nevus"). That the coworkers were not altogether convinced of the legitimacy of pigmented epithelioid melanocytoma as an entity per se and gave circumspection to the possibility of the conditions encompassed by it, namely, animal-type melanoma and epithelioid blue nevus, really being melanoma is evidenced by the facts that (1) they measured the thickness of the neoplasms ("mean Breslow's thickness 3.3 mm"), which never is done for a nevus, and (2) 11 of 41 examples (46%) were found to have metastasized to regional lymph nodes. Curious it is that in 1996, Carney (here a coauthor of Zembowicz and Mihm) along with Ferreiro, in a work devoted entirely to "epithelioid blue nevus," communicated unambiguously that that nevus was benign. [4] That the three collaborators of 2004, however, were less than sanguine about their position in regard to these matters is conveyed by statements by them to the effect they discovered pigmented epithelioid melanocytomas "in the course of a study of borderline melanocytic tumors" and "we suggest that pigmented epithelioid melanocytoma be considered as a provisional histologic entity." It is now incumbent on us, for purposes pedagogical, to set forth, in a manner comprehensive, (1) the criteria of Zembowicz, Carney, and Mihm for diagnosis morphologic of pigmented epithelioid melanocytoma; (2) their concept of animal-type melanoma and epithelioid blue nevus of Carney complex; (3) their definition of terms such as "borderline melanocytic tumors" and "provisional histologic entity", and (4) whatever else of relevancy was written by that trio of authors about the subject of pigmented epithelioid melanocytoma, animal-type melanoma, and epithelioid blue nevus, and about other issues raised by them.

Before proceeding to do that, it is essential that we now take a short detour through the subjects of "blue nevus" in general and of "epithelioid blue nevus" in particular, without which a reader will find unfathomable the concept of "pigmented epithelioid melanocytoma" and will not be able to grasp firmly the gist of our critique of it.