Disseminated blastomycosis diagnosed by fine-needle aspiration of the thyroid

Blastomycosis is an uncommon disease caused by the dimorphic fungus Blastomyces dermatitidis. It can manifest as chronic pulmonary symptoms or disseminated disease. Only three previous cases of blastomycosis involving the thyroid have been reported, of which two were diagnosed by fine-needle aspiration. We present a case of disseminated blastomycosis initially diagnosed by thyroid fine-needle aspiration. Our case was a 47-year-old man with past medical history significant for diabetes, hyperlipidemia, and chronic pancreatitis who presented with a 2-week history of fever, chills, rigors, constipation, and 10 pound weight loss. Abdominal CT revealed chronic pancreatitis and a calcified mass in the pancreas. Chest CT revealed a single 1.5-2 cm thyroid mass and innumerably small 2-3 mm pulmonary nodule bilaterally. Fine-needle aspiration of the thyroid demonstrated 10-20 μm broad-based budding yeasts with thick-walled, refractile capsules amidst a background of granulomatous inflammation, and was diagnosed as a fungal infection consistent with blastomycosis. The patient was started on treatment with itraconazole based upon the FNA diagnosis. Concurrent lung biopsy demonstrated rare possible yeast forms on histology. A specimen from the lung was sent for culture, and was positive for B. dermatitidis, confirming the diagnosis. Disseminated blastomycosis rarely involves the thyroid. However, the thyroid is amenable to fine-needle aspiration. Fungal and mycobacterial cultures and special stains for fungal organisms should be requested on all thyroid fine-needle aspiration biopsies with granulomatous inflammation.