Historical Perspective: K. Smith et al., 1989: "Malignant Spitz's Nevus"

 
In 1989, Smith and coworkers at the AFIP in an article titled, "Spindle cell and epithelioid cell nevi with atypia and metastasis (malignant Spitz's nevus),"42 attempted to justify the designation and concept of malignant Spitz's nevus, which is a contradiction in terms, that is, a malignant benign neoplasm. Of 32 patients who had what they said was a Spitz's nevus, and who ranged in age from 3 to 42 years, 13 of them being 14 years of age or younger, six underwent lymph node dissection and in all six there was metastasis of melanoma. Smith and associates did not provide the age of the six patients with metastases. This is how they described the histopathologic findings in the putative Spitz's nevi:
 
"We have reviewed 32 cases of large melanocytic lesions that extended into the subcutaneous adipose tissue. Many of these cases were clinically suspicious for malignant melanoma. These lesions also showed histologic features that were atypical for benign melanocytic nevi. Those atypical features included a relatively high mitotic rate with mitosis deep within the lesion, lack of maturation of the melanocytes, increased cellularity, increased cellular pleomorphism, loss of cellular cohesion, ulceration, and large size. Although the number of mitoses, lack of maturation, and cellular pleomorphism were greater than in the average S&E [spindle and epithelioid] nevus, these features were not outside the range of S&E nevi . . . All of the lesions had sharp lateral margins, unlike MM [malignant melanoma], which may also consist of spindle or epithelial cells. The deep margin of each lesion also had a smooth, well-circumscribed border (so-called "pushing" border) rather than the irregular infiltrative pattern often seen in MM."
 
Photomicrographs of three of the 32 lesions were shown and even at scanning magnification the diagnosis is melanoma, not Spitz's nevus (Fig. 10). A sheet of neoplastic melanocytes extends throughout the dermis and far into the subcutaneous fat, a finding indicative of melanoma and not of a nevus of any kind. Nonetheless, Smith and collaborators came to these conclusions:
 
"These lesions were thought to represent variants of S&E [spindle and epithelioid] nevi. However, because of their large size and the association of some lesions with lymph node metastasis, the term "malignant S&E nevus" was accepted. Although no definitive conclusions can be drawn from the small number of cases in this study, the benign clinical course in each of these cases, including those with lymph node metastasis, suggests that these lesions have the ability to metastasize to local lymph nodes but are not capable of widespread metastasis. There are documented examples of neoplasms, melanocytic and non-melanocytic, that behave in a similar manner . . . We would not classify these lesions as malignant melanomas because they have not shown the potential for widespread metastases. In conclusion, despite their atypical histologic features, the lesions in this study fit within the spectrum of S&E nevi. Six of the cases in this study showed involvement of lymph nodes that appeared to be metastasis from the cutaneous lesion; however, each of these cases subsequently had a benign course. . . . The benign biologic behavior seen in our series suggests that in some atypical S&E nevi the presence of lymph node metastases may not be sufficient to predict malignant biologic behavior."

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View Figure  		Fig. 10  What was said by Smith and coworkers to be three examples of "malignant Spitz nevus," shown in their figures 1A, B, and C, are malignant melanomas as judged by the silhouette of them, in particular, the dense diffuse infiltrate of neoplastic melanocytes that extends far into the subcutaneous fat. The silhouette of these three neoplasms is just like that of true melanoma as it presents itself in the skin of prepubescent children. We suspect that all three neoplasms came from children younger than 10 years of age and that all three died of metastatic melanoma.
 
The spirit of Helwig was very much present at the AFIP 13 years after publication of his speculation that melanomas in children have a better prognosis because they resemble spindle and epithelioid cell nevus histopathologically.30 The notions of "malignant Spitz's nevus" and "metastasizing Spitz's nevus," however, violate fundamental principles of classic pathology. A Spitz's nevus is a nevus and, like melanocytic nevi of all kinds, is incapable of metastasis. Moreover, the idea that "these lesions have the ability to metastasize to local lymph nodes but are not capable of widespread metastases" also is contrary to rudimentary principles of classic pathology. Once in vascular spaces, either capillaries of blood vessels or lymphatics, malignant neoplastic cells are carried far and wide throughout a system of channels that goes to every nook and cranny of the body. Whether those neoplastic cells will find havens and proliferate in different organs cannot be told; some of them surely do. Moreover, the lymph nodes are not dams or traps, but filters through which neoplastic cells move to more distant sites. It is this fact that explains why the construct of metastasis being separable into categories known conventionally as satellite, in transit, regional, and distant is flawed badly; a satellite metastasis of melanoma is just as grave a sign prognostically as is a distant metastasis because it telegraphs that neoplastic cells have been transported far and wide.
 
Ackerman began to decry the idea of "malignant" and "metastasizing" Spitz's nevus soon after the concept was spawned, and continued to do that in print to the present day.125–127 That that criticism had a salutary effect may be inferred from the title of a presentation to be given by G. Lupton, Head of the Dermatopathology Branch of the AFIP, at the course about Controversies in Dermatopathology at the International Congress of Dermatology in Paris in July, 2002, to wit, "Spitz's nevus cannot metastasize."