Spitz nevus is a benign melanocytic lesion, composed of large melanocytes, round or spindle shaped, with large cytoplasm (spindle or epitheliod cell nevus). Up to 1948, such a lesion was confused with melanoma, due to its atypical histological appearance. The american pathologist Sophie Spitz had the merit to have underlined the diversity of such lesions. In fact, she noted that atypical melanocytic lesions of young patients had a benign outcome, differently from melanoma of adults. The term "juvenile benign melanoma", used by Spitz, is not yet used, as the lesion has been renamed as "Spitz nevus", Such a term, on one hand, refers to the benignity of the lesion and, on the other hand, gives merit to whom firstly recognized it. Of course, the recognition of a benign lesion, which is histologically atypical and therefore simulates melanoma, has made more difficult the diagnosis of cutaneous melanocytic lesions. This, in fact, has shown that histologically features classically associated with malignancy, as nuclear atyipia, could also occur in harmless lesions. Moreover, in the field of melanocytic lesions, the infiltration of the dermis, a feature very useful to establish the malignancy of an epithelial lesion (i.e. squamous cell carcinoma), cannot be used, because generally nevus cells descend into the dermis without being malignant. Spitz nevus, therefore, is a classic simulator of melanoma, which can decept also expert dermatopathologists. The diagnosis of Spitz nevus may be difficult due to the fact that melanoma sometimes simulates Spitz nevus (spitzoid melanoma). Spitz nevus occurs in the childhood and in adult life, more commonly under 30 years. The lesion can grow rather rapidly, then the growth stops and it becomes stable. Generally, it is less than 1 cm in diameter, symmetric, well delimited, and uniformly pigmented. Histologically, it is composed of large round or spindle shaped melanocytes, often atypical. Epidermal melanocytes are often arranged in nests, well delimites by clear semilunar clefts. Spindle shaped cells are often vertically oriented, single cells are scant. Frequently, suprabasal melanocytes, simulating pagetoid infiltration of melanoma, may be observed (pseudoinfiltration)(see page 4). In the dermis, melanocytes tend to become smaller as they descend deeply. The epidermis is hyperplastic; angiectases and lymphocytic inflammatory infiltrate occur in the dermis. Mitoses are rare and limited to the superficial part of the lesion.

page 8

The other pages