In Reply

In Reply.—We thank Douglas Craig Miller, MD, PhD, and authors Alireza Sepehr, MD, and Steven R. Tahan, MD, for their interest in our article reviewing the topic of borderline melanocytic tumors.1 In that article, we sought to provide logical and reasoned arguments, underpinned by biological and clinical evidence, supporting the hypothesis that there exists a small but significant subset of melanocytic tumors that have a limited capacity to metastasize to local lymph nodes but rarely spread to distant sites. We pointed out that this subgroup of tumors has a much more favorable prognosis than “conventional” melanomas and that the well-known, important prognosticators for conventional melanomas, such as tumor thickness and sentinel lymph node tumor-harboring status, do not appear to have the same significance for them.2–17 These facts support our proposal that such melanocytic tumors are biologically distinct and should be classified in a nosologic category separate from both melanomas and nevi.This concept is not new. In 1989, Smith and colleagues18 reported a series of tumors, which they interpreted as Spitz nevi, that involved regional lymph nodes but had not spread further to more-distant sites. Similarly, blue nevi metastasizing to lymph nodes have also been reported.19–21 Although some of these previously reported, metastasizing Spitz nevi and blue nevi have since been reinterpreted as melanomas,22,23 numerous large series with significant follow-up have highlighted the apparently favorable outcome of some “borderline” melanocytic tumors associated with regional lymph node metastases, such as atypical Spitzoid tumors and pigmented epithelioid melanocytomas.2,5,8–18,24 Despite this compelling evidence, Drs Sepehr and Tahan contend that even larger studies with longer follow-up are required before they will consider it appropriate to recognize additional, biologically distinct subgroups of melanocytic tumors. This begs the philosophic and rhetoric question, “How much evidence is required to challenge accepted dogma and present new hypotheses that better explain the data?”Whether or not the term melanocytoma, as we have proposed, is the best term for this distinct subset of tumors or another term, such as low-grade melanoma or perhaps borderline-malignant melanoma (akin to borderline ovarian carcinoma), is preferable is clearly controversial, as shown by the correspondence and remains a topic for further debate. Nevertheless, the evidence is already clear that the clinical behavior of these tumors justifies classifying them in a disease subgroup separate from both nevi and melanoma. Perhaps, in time, some tumors currently classified as atypical Spitzoid tumors and atypical deep penetrating nevuslike tumors will become known as Spitzoid melanocytomas and deep-penetrating melanocytomas, respectively. Furthermore, melanocytoma occurring in the central nervous system, which may recur or show invasive growth,25 could be termed central melanocytoma.Finally, in their correspondence, Drs Sepehr and Tahan mention the hypothetical case of an ulcerated, 5-mm-thick melanocytic tumor with 9 mitoses/mm2 occurring in an 80-year-old patient, which they classified as an atypical Spitzoid tumor. We respectfully disagree with the suggestion that any melanocytic tumor with these characteristics, particularly the high mitotic rate in a patient aged 80 years, should be classified as an atypical Spitzoid tumor. In our opinion, these features strongly suggest that the tumor is, in fact, a bona fide melanoma.