3、Clinical

     ● Usually single, but may also be multiple and clustered (agminate) or multiple and disseminated

    ● Benign, but may recur if incompletely excised or even if “clinically removed”

    ● May involve regional lymph nodes, particularly in atypical lesions

    ● Misdiagnosis of melanoma as Spitz nevus is common cause of malpractice claims

4、Sites

7、Micro description

● Symmetric with sharp lateral borders, usually compound nevus with prominent intraepidermal component

● 5% are junctional, 20% are dermal

● Composed of spindle cells and epithelioid cells

● Spindle cells may be arranged in fascicles in the dermal papillae, perpendicular to epidermis, are cigar shaped with large nuclei and prominent nucleoli

● Epithelioid cells are dispersed individually, are polygonal with abundant eosinophilic cytoplasm, distinct cell borders, large nuclei and prominent nucleoli, variable mitotic figures, occasional multinucleation, often marked atypia, although most cells appear benign

● Cell maturation occurs in deep portion of tumor

● Also large and well formed Kamino bodies (eosinophilic hyaline bodies along dermoepidermal junction)

● May have pagetoid growth, lymphatic invasion, pseudoepitheliomatous hyperplasia, “tubular” growth pattern, plexiform growth pattern, halo reaction, prominent vasculature (Am J Dermatopathol 2000;22:135), lymphocytic infiltrate

● Scanty pigmentation

● “Consumption of epidermis” (usually associated with melanoma) is seen in 10% of Spitz nevi, defined as thinning of epidermis with attenuation of basal and suprabasal layers and loss of rete ridges in areas of direct contact with neoplastic melanocytes (AJSP 2004;28:1621)