Melanocytic nevi and melanoma: overlapping criteria—the degree is the key

Summing up, the concept of the degree of criteria is the key to overlapping subjective criteria in melanocytic proliferations. This is the lesson to be learned. Although criteria that are used to come to a diagnosis of melanoma are well known and as a whole accepted, it is the degree or number or quantity of criteria, that is a few or many, that are vitally important, and at times crucial to arrive at the correct diagnosis of melanocytic nevus or melanoma. Until the time when there is a definitive litmus test to differentiate a melanocytic nevus from a melanoma with absolute certainty, the degree of overlapping criteria will remain essential, even though misdiagnoses will, from time to time, continue to occur. Fittingly, the words of the late A. Bernard Ackerman, M.D., who during his career was incredibly unrestrained and exceptionally passionate on the subject of melanocytic neoplasia, are to the point: “The effort here at characterization accurate of the changes is defensible, but not verifiable! It being subjective, as are all judgments predicated on observations morphologic” [6].


Introduction
Gross and microscopic criteria are morphologic and thus subjectivity abounds for the pathologist in the diagnosis of benign and malignant melanocytic proliferations [1].
The state-of-the-art criteria, often touted to be definitive, delineates between benign and malignant conditions clinically and histopathologically. This issue becomes murky, however, when the same criteria, on occasion, are present in both benign and malignant entities. This twist of fate is commonly referred to as overlapping criteria. This is exemplified frequently in benign melanocytic proliferations, i.e., melanocytic nevus and its variants (so-called combined nevus, Spitz's nevus, juvenile melanoma, dysplastic nevus, atypical nevus, nevus with architectural disorder and sever/moderate cytologic atypia, deep penetrating nevus, Reed's nevus, spindle-cell tumor, pre-melanoma, borderline melanoma, and recurrent/persistent melanocytic nevus, all of which are nothing more than a benign melanocytic nevus with findings focal common to those of the infamous melanoma. Overlapping criteria in benign and malignant melanocytic proliferations are well known and expected findings [1][2][3]. Because of the confusion that overlapping criteria create, it is essential to separate those proliferations truly benign from those that are in fact malignant. Furthermore, it is important, if not imperative, to recognize the degree of criteria, i.e., mild, moderate or extensive. In other words, is the criterion or criteria, an occasional finding, focal, isolated, or diffuse? What is the degree of criteria? Is it just happenstance, and does it matter? This is the question. The assessment of the degree of criteria is of the essence in order to arrive at an accurate diagnosis and avoid a misdiagnosis.

Discussion
The spectrum of criteria to differentiate a melanocytic nevus from melanoma is variable. Clinically, the criteria are few in number and include asymmetry, border, color, and diameter.
However, many of the acknowledged criteria for the clinical diagnosis for melanoma may be found in other benign or malignant proliferations, such as melanocytic nevus, seborrheic keratosis, hemangioma, adnexal proliferations, basal and squamous-cell carcinoma, and lymphoma, to mention but a few. However, microscopically the criteria for melanoma are diverse and at times perplexing. They include asymmetry, poor circumscription, cellular/nuclear jumbling or crowding, atypia, pleomorphism, nuclear hyperchromatic and heterochromasia, melanoma because on occasion, if not repeatedly, they may be found in some benign melanocytic nevi. Therefore, it is crucial to consider the degree of the findings. In other words, the finding of a single, isolated criterion, which may occur in defensible, especially and regularly in medico-legal issues [5].
To be precise, overlapping criteria and the various range of degree of criteria, as a consequence, expose the practice of medicine and pathology for what they are: an ever changing, imperfect as well as a vexing science. Certainly, our individual concepts, views, beliefs and bias formed during and after our formal educational process (which by the way never ends) are significantly affected and powerfully influenced by our own and our mentor's interest and zeal, and how!

Summary
Summing up, the concept of the degree of criteria is the key to overlapping subjective criteria in melanocytic proliferations.
This is the lesson to be learned. Although criteria that are used to come to a diagnosis of melanoma are well known and as a whole accepted, it is the degree or number or quantity of criteria, that is a few or many, that are vitally important, and at times crucial to arrive at the correct diagnosis of melanocytic nevus or melanoma. Until the time when there is a definitive litmus test to differentiate a melanocytic nevus from a melanoma with absolute certainty, the degree of overlapping criteria will remain essential, even though misdiagnoses will, from time to time, continue to occur. Fittingly, the words of the late A. Bernard Ackerman, M.D., who during his career was incredibly unrestrained and exceptionally passionate on the subject of melanocytic neoplasia, are to the point: "The effort here at characterization accurate of the changes is defensible, but not verifiable! It being subjective, as are all judgments predicated on observations morphologic" [6].