Gastrointestinal basidiobolomycosis. Morphologic findings in a cluster of six cases.

We describe the histopathologic features of 6 cases of gastrointestinal basidiobolomycosis examined at 4 Phoenix, AZ, area hospitals during the last 4 years. Resected stomach and intestinal specimens were characterized by marked mural thickening with fibrosis, prominent tissue eosinophil infiltration and palisading granulomatous inflammation around pale fungal hyphae. In 2 cases, there was colonic perforation. Basidiobolus ranarum hyphae (associated with spore-like spherules in 4 cases) were identified within tissue sections; the irregularly branched, thin-walled, occasionally septated hyphae were typically surrounded by a thick eosinophilic cuff (Splendore-Hoeppli phenomenon). Although the histologic features of B ranarum are well described in the skin and subcutaneous tissue, gastrointestinal involvement has presented considerable diagnostic difficulty. Before the occurrence of this cluster of cases, intra-abdominal B ranarum infection has been reported only rarely.