[Approaches to the dermatopathologic diagnosis of figurate lesions]

Both clinical and pathologic findings must be considered when diagnosing figurate skin lesions, which are often seen in routine practice. Although a skin biopsy may sometimes be diagnostic, more often the information provided is nonspecific. In an attempt to offer an approach to diagnosing these dermatoses, we have classified annular lesions according to the presence of lymphocytic, neutrophilic-eosinophilic, or granulomatous infiltrates, and infiltrates containing plasma cells. Neoplastic annular lesions are included in a separate group. Lesions containing lymphocytic infiltrates include superficial and deep erythema annulare centrifugum and the differential diagnosis includes a large number of conditions. In the neutrophilic-eosinophilic class, we include annular psoriasis, vasculitis, linear immunoglobulin A dermatosis, eosinophilic dermatitis, erythema marginatum rheumatica, and annular erythema of infancy. Sarcoidosis and granuloma annulare are the prototypical annular lesions containing granulomas. Secondary syphilis is typical of lesions containing plasma cells. Mycosis fungoides is the principal skin tumor that may initially manifest with annular lesions.