Spitz nevus

History

Sophie Spitz, a pathologist at Memorial Sloan Kettering, published a series of 13 patients in 1948, under the title ‘Melanomas of childhood’. While there had been some previous observations of lesions that were probably Spitz nevi, her paper is generally credited with outlining the entity, even if she viewed it in 1948 as a form of melanoma. She noted a variety of clinical appearances, from small to large lesions, some smooth and some verrucous. She observed no differences histopathologically between ‘melanoma of childhood’ and melanomas in adults, save for the presence of giant cells in the former group.

A concise description of the histopathologic features of ‘melanomas’ of childhood did not emerge for years. Spitz and Allen re-evaluated similar cases, concluding that the ‘melanomas’ in question were actually benign. The term ‘spindle and epithelioid cell nevus’ came into common use a few years later, reflecting the dominant cell types found in these lesions.

Progressively more detailed observations, most notably those by Paniago-Perreira, Maize and Ackerman in 1978, established some criteria for differentiating Spitz nevi from melanoma. A. Bernard Ackerman, who trained initially as a dermatologist before specializing as a dermatopathologist, brought more of a clinical bent than previous observers, and some of his criteria (e.g. circumscription and symmetry in Spitz nevi) reflect the correlates of clinical observations. The last two decades of the twentieth century, and the first decade of the twenty-first century, saw detailed morphologic studies of Spitz nevus and of its many variants. In 1989, a paper by Smith and colleagues from the Armed Forces Institute of Pathology cast doubt on the idea that there was a clean dichotomy between Spitz nevus and melanoma, but the benign/malignant paradigm dominated most articles, textbooks and clinical practice. The last several years have seen increasing questioning of this paradigm, and the limitations of clinical and histopathologic criteria in the differential diagnosis.

Clinical features

The clinical features of Spitz nevus were overly simplified in early reports, ignoring the diverse appearances that Spitz noted. Also, because Spitz noted that children with melanoma had a more favorable course than adults, her nevus was initially believed to only occur in children. Spitz and Allen later did note the occurrence of their lesion in adults, and this observation was expanded in a series by Weedon and Little. An accurate assessment of the age distribution of Spitz nevus did not come for many years, probably because identical lesions in middle-aged and older adults were diagnosed as melanoma.

The clinical diversity of Spitz nevus is remarkable. Lesions vary in size, with some stabilizing after reaching a few millimeters in diameter ( Fig. 31.1A–E ) while others grow to several centimeters. Most have sharp, even borders, and are symmetrical. Their surfaces vary from smooth to warty and scaly. They vary from bright red (lesions of this appearance are mistaken for hemangiomas) to tan, brown and nearly black. Usually, only one color is present, unlike the case in melanoma. The near-black lesions are often pigmented spindle cell, or Reed's, nevi. Reed's nevi seem to be a distinctive clinicopathologic form of Spitz nevi (see below). Rare Spitz nevi elicit a halo reaction, and are surrounded by a collar of depigmented skin.