Nodular subcutaneous histoplasmosis. A case report with diagnosis by fine needle aspiration biopsy.

Fine needle aspiration biopsy (FNAB) of a solitary subcutaneous nodule in the upper arm of a patient being treated with corticosteroids for chronic obstructive pulmonary disease contained numerous spherical, unstained, refractile particles mixed with necrotic cellular material and rare intact histiocytes with yeastlike inclusions. The morphology of the extracytoplasmic spheroids and cytoplasmic inclusions, as demonstrated with Gomori methenamine silver stain, was characteristic of Histoplasma capsulatum var capsulatum. This organism's identification was confirmed by excisional biopsy and microbiologic testing. If the characteristic intrahistiocytic, yeastlike forms are rare or absent, recognition of this peculiar, uncommonly encountered extracellular pattern is crucial to the diagnosis of infection with H capsulatum. This pattern may become more common with increased numbers of immunosuppressed patients and increased use of FNAB.