Atypical Spitz Tumor Versus Dermatofibroma: Two Case Reports Highlighting a Diagnostic Challenge

Spitzoid tumors comprise a heterogeneous spectrum of melanocytic neoplasms, ranging from benign Spitz nevi to malignant Spitzoid melanoma, with atypical Spitz tumor (AST) representing an intermediate entity of uncertain biological potential. AST is a rare melanocytic lesion that may clinically mimic non-melanocytic tumors, particularly dermatofibroma, making accurate diagnosis challenging. It predominantly affects children and young adults and has a predilection for the lower extremities. We describe two cases of young female patients presenting with clinically similar erythematous-pigmented plaques on the thigh. Despite comparable clinical appearances, dermoscopic evaluation revealed distinct patterns that led to different diagnoses: a spitzoid melanocytic proliferation (confirmed as AST on histology) and a dermatofibroma, with markedly divergent biological behaviors and prognostic implications. In spitzoid lesions, the presence of dotted vessels, shiny white streaks, inverse pigment network, and/or brown globules should raise suspicion of a melanocytic spitzoid proliferation. In contrast, the dermatofibroma exhibited a peripheral pigmented network, a central scar-like white area, and brown ringed globules, consistent with the typical dermoscopic pattern of this benign fibrohistiocytic tumor. These observations underscore the value of dermoscopy as a diagnostic triage tool in the assessment of spitzoid lesions. However, definitive diagnosis still relies on histopathological evaluation.