Historical Perspective: Rapini, 1999

 
Rapini, in an article in 1999132 that dealt with the conundrum, "Spitz nevus or melanoma?", offered these thoughts about the subject of "malignant Spitz's nevi:"
 
" The unfortunate controversial name "malignant Spitz nevus' refers to those that metastasize to regional lymph nodes, yet they are still thought to be benign, because no further dissemination occurs and the patient appears to do well. This is because the presence of melanocytic rests within lymph nodes is not invariable evidence of malignancy. For example, very large congenital melanocytic nevi can be accompanied by apparently benign rests of melanocytes within nodes, and the situation with malignant Spitz nevus is presumed to be similar. However, it is difficult to be certain about the significance of lymph node involvement, and the diagnosis of malignant Spitz nevus remains very controversial. Malignant Spitz nevi in the skin tend to be larger and deeper, with more necrosis, ulceration, cytological atypia, and mitoses than average idealized Spitz nevi."
 
In these lines, Rapini gave tacit approval to the idea of "malignant Spitz's nevus," a notion that deserves no approval because no such neoplasm exists; so-called malignant Spitz's nevus is a melanoma. Rapini went on to advise about which histopathologic findings he found useful for distinguishing Spitz nevi from melanomas and he did that in these lines:
 
" . . . Spitz nevi tend to be sharply demarcated in the epidermal component, whereas melanomas often have an intraepidermal radial growth that seems to sputter along for a less distinct distance. Melanomas are more likely to be asymmetric, but exceptions occur, especially in nodular melanomas. The melanocytic cells in the deeper portion of Spitz nevi tend to be smaller and less atypical, and this is often called maturation. . . . Nest size tends to be uniform from side to side in Spitz nevi, and is more variable in melanomas. . . . Mitoses can be seen in both Spitz nevi and melanomas. Mitoses close to the base of the lesion are more common in melanomas. Bizarre or highly abnormal morphologies of mitoses are more often seen in melanomas. Pagetoid melanocytes can be seen in both melanomas as well as Spitz nevi, but they tend to involve single cells rather than nests in melanomas, and in melanomas they tend to spread into the poorly demarcated shoulders of the lesions. . . . The most helpful differentiating features of Spitz nevi are patient age, sharp demarcation, symmetry, maturation of melanocytes at the base, and epithelial hyperplasia."
 
Although some of the observations of Rapini surely are correct, some, such as those about the age of a patient being a criterion for diagnosis, an intraepidermal radial growth being an attribute of melanoma only, and pagetoid melanocytes being a finding in Spitz's nevi are plain wrong.