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Primary melanoma
Primary melanocytic neoplasms commonly present problems in histologic differential diagnosis. In addition, the interpretation of such lesions is complicated by controversy regarding the nature of some melanocytic neoplasms. Some lesions, that might deserve separate recognition, have not been accepted as entities and have not been adequately studied. Some lesions have been accepted as entities and extensively studied, but the criteria for diagnosis have not been discriminative; lesions that have metastasized have been included in some “benign” categories to a degree that serious questions exist as to the nature of the lesion. Hospital pathologists who have depended on the criteria of some “experts” have found their diagnoses sometimes fail to be congruous with the subsequent clinical course; they have found themselves accused of malpractice.
The concept of Minimal deviation melanoma gave recognition to uncommon melanocytic lesions which share features with some variant “nevi” but on occasion metastasize to regional lymph nodes, or result in progressive disease. The concept has been subjected to politicizations which have more or less negated its usefulness. Some of the criticisms are closely related to a “need” to promote certain personalized criteria for the diagnosis of certain “nevi.” Experts, having encountered problems in attempting to promote their criteria in the face of the concept of MDM (the criteria in the concept of MDM seemed to contradict some of the personalized criteria), have worked to discredit the concept of MDM. These controversies are something more than philosophical discourses; ego has played a great role in where we are today in reference to an understanding of neoplasms that have “nevus-like” qualities (the uncertain nature of both “halo nevus-like” lesions, and “ Spitz nevus-like” lesions can be cited as a prime examples).
The problems encountered in both the pretrial, and the court proceedings of malpractice claims are different from the politics of the practice of pathology, but are of a political nature. The experts for the two adversaries have, by agreeing to participate, chosen opposing sides; they, as well as the plaintiff and the defendant, are adversaries. The legal profession attempts to disguise this flaw, but in the proceedings the lawyers exploit the commissions of the experts. There is little about an expert’s role that should produce a sense of satisfaction, either at the immediate end of court proceedings in which a judgement has been in favor of one expert’s position, or months or years later after the role of the expert can be thoughtfully evaluated. Plaintiff’s lawyers can be ruthless schemers. Experts may engage more in character assignations than in the delivery of scientific data. An expert, who is involved as a defendant in a malpractice case while finding fault in a separate case with the performance of a hospital pathologist (with almost identical settings of wrong diagnosis of a problem lesion for both the expert and the hospital pathologist) is not just a hypocrite; he is actually a prostitute.
This chapter is the parent for several pictorial chapters. I have selected cases that, in my opinion, offer a challenge to the reader. Histologic descriptions will be provided; in addition, the cases will be evaluated by guidelines in the concept of MDM. Obviously, the reader may choose to ignore the guidelines. I would encourage the reader to arrive at his own interpretation, and then compare his diagnosis with whatever I provide. I will try to be objective in my interpretations of the material. As is the case for much of the material on this site, the photomicrographs from which the digital pictures have been derived are old; in addition, the quality of the initial histologic sections was extremely variable.
The PICTORIALS that are “children” of this chapter include a several variations of melanocytic neoplasia. Two of the cases introduce the concept of spontaneous regression. It seems that regression is often given primacy in the interpretation of such lesions; it is as if regression is a process that promotes metastases; perhaps, this is the case, but it seems more logical (to borrow Dr. Ackerman’s emphasis on logic) to indict the component which has undergone regression as the prime prognostic determinant. The possibility that regression opens vascular avenues in a permissive manner should be considered, but physical dimensions of the component that has gone away would certainly have been of interest. One of these two lesions lacks a convincing component of atypical cells; the nevus cell component which is represented shows focal areas of fibrosis that are of a common type in the setting of a small congenital nevus.
One of the lesions with focal regression, also shows small vertical growth-like components, and the basic patterns of a thin SSM. The small vertical growth-like components, if evaluated by Breslow’s criteria, would measure less than 1 mm in vertical dimensions; such a lesion, by physical dimensions, would qualify as a borderline melanocytic neoplasia of indeterminate malignant potential.
One lesion is composed of pigmented spindle cells. For this lesion, the options are many. If the collection of virtual images which have been structured and then stored by the observer for the interpretation of “Spitz nevi” are selected, there are many features which are congruous. For the few who work at the diagnosis of MDM, the lesion might evoke images of the pigmented spindle cell (non-Spitz type) variant. A variation of blue nevus might be considered. Even combined nevus might be considered.
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