This is what was said by Zembowicz et al. about animal-type melanoma: "The term animal-type melanoma was applied in the human pathology literature to unusual heavily pigmented melanocytic tumors with unpredictable clinical course because of their histologic similarity to melanocytic tumors in equine melanotic disease. As the number of published examples was small, the concept of animal-type melanoma in humans has not received wide acceptance and the appropriateness of the term has been questioned. Some cases that we (M.C.M., A.Z.) have considered as animal-type melanoma were interpreted by outside pathologists as atypical nevi. Especially intriguing to us was resemblance of human animal-type melanoma to epithelioid blue nevus, initially described in patients with Carney complex, but also reported in sporadic setting outside the complex."

This is what the collaborators wrote about epithelioid blue nevus: "We compared histologic features of pigmented epithelioid melanocytoma to those of 10 cases of epithelioid blue nevus from patients with Carney complex and one additional previously unreported case. This comparison included independent review of the cases by the authors and a common session at a multiheaded microscope. The review showed that the histologic features of pigmented epithelioid melanocytoma were indistinguishable from epithelioid blue nevus of Carney complex. Twenty-six [sic] of 41 cases were considered identical by all three authors. Fifteen of 41 cases were ranked identical by at least one author and were considered very similar by all. Ulceration was the only formally evaluated histologic feature different between the two groups of lesions. It was not present in Carney complex."

The assessments just quoted of the three fellow workers led them to conclude the following:

They went on to state that "In particular, we found no correlation between the presence of ulceration, degree of cytologic atypia or mitotic activity, and the findings of lymph node metastasis."

Despite these assertions concerning the oneness of pigmented epithelioid melanocytoma, animal-type melanoma, and epithelioid blue nevus of Carney complex (" . . . it is best to consider pigmented epithelioid melanocytoma as . . . synonymous with both animal-type melanoma and epithelioid blue nevus"), the associates nonetheless could write these lines sobering: "The relationship between melanoma in animals and pigmented epithelioid melanocytoma also remains to be resolved. It was the similarity of features between them (histologic findings, indolent clinical course, and apparent lack of association with sun exposure) that stimulated us to introduce the concept of animal-type melanoma in humans."

Just as the coauthors neglected to inform of why on the basis of findings histopathologic, animal-type melanoma qualified as a malignant neoplasm, so, too, it was for them in regard to epithelioid blue nevus of Carney complex. Nowhere in the article by Zembowicz, Carney, and Mihm is a single criterion offered that enables the condition under consideration by them, i.e., pigmented epithelioid melanocytoma—animal-type melanoma—epithelioid blue nevus of Carney complex, to be judged malignant. Although the presence of melanocytes in a lymph node is a finding expected in some congenital nevi known, generically and all-inclusively, as blue nevi, the fact that some patients of Zembowicz et al. with pigmented epithelioid melanocytoma had deposits of abnormal melanocytes in the parenchyma of nodes seems to force to a position reasonable that those accumulations represented metastases. It is interesting to note, also, that not a syllable was devoted by the team of three to the matter of whether horses with so-called animal-type melanoma ever died as a consequence of metastases.

In brief, no matter how thoroughly the article titled, "Pigmented epithelioid melanocytomas: a low-grade melanocytic tumor with metastatic potential indistinguishable from animal-type melanoma and epithelioid blue nevus" is scoured, it is impossible to come away with a concept clear of how that diagnosis (including animal-type melanoma and epithelioid blue nevus) is made with confidence on grounds morphologic, that is, clinical and histopathologic. No matter how intently the article is scrutinized, it cannot be determined why those neoplasms designated pigmented epithelioid melanocytoma and that metastasized were not melanomas. In fact, that is just what they were. And if the lesions that did not metastasize truly were indistinguishable from those that did, then they, too, must have been melanomas!