Palisading granulomas caused by infectious diseases.

We recently encountered a palisading granuloma in which an infectious cause was not considered until special stains revealed hyphae and tissue culture revealed organisms of phaeohyphomycosis. A review of more than 2,500 cases of various granulomas revealed 11 cases of palisading-type granuloma caused by infection, including phaeohyphomycosis, nontuberculous mycobacteriosis, papulonecrotic tuberculid, tuberculoid syphiloderm, cat-scratch disease, sporotrichosis, cryptococcosis, and coccidioidomycosis. Infectious disease should be considered in the differential diagnosis of palisading granuloma. Special stains for bacteria, fungi, and acid-fast bacilli should be performed in biopsy specimens that have a palisading granuloma pattern with central necrosis, especially in immunosuppressed patients.