Pseudofungi in Pericolic Lymph Nodes

Abstract

Abstract We report a case of extensive pseudofungi in the pericolic lymph nodes. A 45-year-old man presented with lower abdominal discomfort, and large solid and cystic masses were discovered in the pelvic cavity by computed tomography. Debulking of the masses (by means of a Hartmann operation) was performed under the clinical impression of a pelvic sarcoma, and histologically the masses demonstrated features of a malignant gastrointestinal stromal tumor. All pericolic lymph nodes demonstrated multiple septate hyphae–like structures with pigmentation, particularly in the subcapsular sinuses. These structures showed positive staining with periodic acid–Schiff, but Gomori methenamine silver staining was negative. The structures appeared to be composed of iron, phosphorus, and calcium by Perls iron and von Kossa stains and revealed deposition of electron-dense granules on electron microscopic examination. Energy-dispersive radiographic micro-analysis showed the structures to contain phosphorus, sulfur, potassium, calcium, and iron. Pseudofungi can be misinterpreted as true fungi with septate hyphae; therefore, a careful morphologic examination with appropriate special stains is mandatory.