Blastomycosis: contributions of morphology to diagnosis: a surgical pathology, cytopathology, and autopsy pathology study.

Blastomycosis is caused by the inhalation of spores of the dimorphic fungus, Blastomyces dermatitidis. The reporting of this disease is not required by all states. The diagnosis is established by culture or by identification of broad budding yeast forms in tissue or cytology samples. A retrospective review of blastomycosis was conducted using surgical pathology and cytopathology records of a large community based general hospital, for the years 1982 to 2002; the autopsy records of a university referral center were searched for the years 1992 to 2004. Thirteen surgical/cytology cases were retrieved: 8 localized to the lung (group 1) and 5 with extrapulmonary presentation (group 2). Three of the former were clinically thought to be tumors. Broad-based budding yeast forms with thick cell walls were seen in all but 1 case and identified on conventional routinely stained preparations. Microbiologic culture was positive in 2 lung cases only, in 1 of which it was the sole means of diagnosis. Culture was negative for Blastomyces in the only extrapulmonary case for which a specimen was submitted. One patient in group 2 died, but had a coexistent disseminated gastric adenocarcinoma. No autopsy was performed. Three autopsies of blastomycosis were recovered (group 3). Two patients were on corticosteroids and 1 was diabetic. Premortem diagnoses were established only within a few days of death in 2 patients. Blastomycosis is seldom a fatal disease. Most patients are immune competent; immune compromise favors an aggressive course. Microbiologic culture and conventional morphologic assessment of routine samples have redundant utility in diagnosis.