The title given by Pearson et al. [10] to their article alerts a reader reflective to shoals intellectual ahead (Fig. 2). What, pray tell, is the difference between a "malignant melanotic neurocristic tumor" and a melanoma, and between a "neurocristic hamartoma" and a "blue nevus" of one kind? No answer is given.

And if there is a "common melanoma," then there must be an "uncommon melanoma," but the authors fail to define that either, thereby leaving a reader wanting. From the text it can only be inferred that for Pearson et al., "common melanoma" is that "arising in the epidermis." which implies that melanoma uncommon originates elsewhere, the where not being identified.

Neoplastic melanocytes in the epidermis is a finding near invariable in primary cutaneous melanoma, but it is neither specific nor necessary for diagnosis of it, as witnessed in some examples of desmoplastic melanoma and of melanoma in prepubescents. Moreover "arising" is not determinable by inspection alone; abnormal melanocytes disposed as solitary units and in aggregations of different sizes and shapes "pepper" the epidermis of "epidermotropically metastatic" melanoma, which at times may be impossible to differentiate histopathologically with surety from melanoma primary in the skin.

Concerning neurocristic hamartoma (no longer modified by "pilar"), the authors had this to say: "We define the neurocristic hamartoma as a pigmented lesion of the skin and superficial soft tissues composed of a complex proliferation of nevomelanocytes, schwannian cells, and pigmented spindled and dendritic blue nevus cells." [10]

What is a "complex proliferation" and what are nevomelanocytes? Are they not abnormal melanocytes? And what are "dendritic blue nevus cells"? Are they not abnormal melanocytes, too? Because no evidence of "schwannian differentiation" is presented in any of the seven cases, we are compelled to conclude that such differentiation is not a sine qua non for diagnosis of neurocristic hamartoma, which seems also to be the stance of Pearson et al., but not of Tuthill et al. And if we accept the definition of Pearson et al., any congenital nevus would qualify as a neurocristic hamartoma. In the lines that follow, those collaborators seem to confirm our interpretation of their own thinking about the matter: "Admittedly, any one field from one of our cases may closely resemble a combined nevus, a cellular blue nevus, a congenital blue nevus, and so on, but it is the unusual combination of cell types, their tissue distribution, clinical appearance, and propensity for continued growth and the eventual development of CMMNT [cutaneous malignant melanotic neurocristic tumor] that set cutaneous neurocristic hamartoma apart from more common melanocytic nevi." [10]

Apart from the opaqueness in general of that very long sentence, no mention is made of "schwannian differentiation" being requisite for diagnosis of neurocristic hamartoma. It is firmly established that congenital nevi are protean in regard to "unusual combinations" of cells and patterns; that most combined nevi are congenital; and that cellular blue nevus is congenital and, therefore, the term "congenital blue nevus" is a redundancy. According to Pearson et al., diagnosis of neurocristic hamartoma requires knowledge of its "propensity for continued growth and the eventual development of cutaneous malignant melanotic neurocristic tumor." which means that the diagnosis turns on aspects biologic, not attributes morphologic!

A congenital nevus that is giant and hairy is a hamartoma, the terminal hairs that blanket it springing from terminal follicles at a site anatomic where hairs and follicles normally are vellus, they being constituents, in addition to abnormal melanocytes, of the hamartoma. But Pearson et al. fail to inform what criteria histopathologic are requisite for a congenital melanocytic nevus to qualify as being "neurocristic." Do not all melanocytes of all melanocytic nevi derive from the neural crest and in that sense are not all of them "neurocristic"? Viewed from that perspective, replacing the term "congenital nevus" by "neurocristic hamartoma" is no great achievement and brings nothing original or illuminating to the subject. As a matter of fact, it confuses.

Concerning the component "pilar" of neurocristic hamartoma, as it was characterized initially by Tuthill et al., Pearson et al. had this to say: "Surrounding the tumour in the dermis were nevomelanocytic cells that matured into pigmented spindle cells that formed whorls and fascicle investing adnexal structures." [10]

Although adnexocentricity is characteristic of many kinds of congenital nevi, among those "superficial and deep," "deep penetrating," and "blue," especially of the type "cellular" and "neuro of Masson." the authors nevertheless interpret that phenomenon in this way: "Although follicular epithelium is not derived from the neural crest, neurocristic derivatives in the dermis may influence the induction of follicular epithelium that buds off the epidermis." [10]

Yet again, mysticism triumphs over rationality; in fact, there is no evidence, whatsoever, that "neurocristic derivatives" in the dermis induce follicles to "bud off the epidermis." In short, for Pearson et al., the distribution perifollicular of pigmented cells is not an early and specific characteristic of the hamartoma, as it was for Tuthill et al. in 1982, but the result of induction of follicular epithelium by the hamartoma neurocristic. In that formulation, the roles of "neurocristic derivatives" and "follicular epithelium" have become reversed!

The speculation of Pearson et al. only brings more befuddlement to a subject already fogbound. But still more perplexity is brought (if that were possible!) by the legend of Pearson et al. to Figure 8, which pertains to characteristics cytopathologic of the lesion, they being described thus: "(a) An important feature distinguishing cutaneous malignant melanotic neurocristic tumor from common melanoma is that most consisted predominantly of small round cells with bland nuclear features. (b) Two cutaneous malignant melanotic neurocristic tumors arising in neurocristic hamartomas were composed predominantly of overtly malignant large epithelioid cells in a nested pattern." [10]

Which is it? Is cutaneous malignant melanotic neurocristic tumors arising in neurocristic hamartomas made of "small round cells with bland nuclear features" or of large "overtly malignant large epithelioid cells." or both, or neither? It is left to the helpless reader to decide and that poor soul victimized repeatedly succumbs to the message of the authors, sent between the lines and beyond them, that if all of the patter by them is not clear abundantly and immediately, then something surely is wrong with the reader!

For Levene,[4,7] atypia of cells constituent was the main criterion for defining "frank malignancy," whereas for Pearson et al., most of the neoplasms malignant were composed of cells that displayed no nuclear atypia, e.g., "small round cells with bland nuclear features." In our estimation, the lesions described by Pearson et al. are melanomas that developed in the substance of a congenital nevus and, that being so, there is no need to invoke a concept as obscure as that of cutaneous malignant melanotic neurocristic tumor. The attributes architectural that so impressed the authors are not unusual for either congenital nevi or for melanomas.

Pearson et al. advise that the behavior biologic of cutaneous malignant melanotic neurocristic tumor is more favorable than that of "common melanoma." despite the fact that 4 of their 7 patients died of metastases 2, 6, 8, and 20 years, respectively, after a diagnosis of melanoma primary had been established, whereas only 1 was alive with metastases after 3 years. Is the behavior of "common melanoma" less favorable than that?

Last, although no reference specific is made in the article by Pearson et al. to equine melanocytic disease, we have included their work in this review not only because the ill-defined concept of "neurocristic hamartoma" has been linked so often to equine melanotic disease, but to illustrate how dramatic can be the degeneration of a concept that is defective irremediably.