A 54 year old farmer presents to his physician with chronic cough. Chest x-ray demonstrates a mass lesion with hilar lymphadenopathy. Biopsy of the mass demonstrates multiple, tiny yeast forms within macrophages. Which of the following is the most likely diagnosis?

Histoplasmosis is caused by Histoplasma capsulatum, a dimorphic fungus that grows as a mold in the wild, but as a tiny yeast inside macrophages in humans. The disease is typically asymptomatic or mild enough to go undetected, but when symptomatic, it presents with cough, fever, and malaise. Blastomycosis is characterized by a larger, round-budding yeast form, seen free in the tissues. Coccidioidomycosis is seen mainly in the dese pas of the Southwest U. S. In the lungs, spherules containing endospores are seen. Paracoccidioidomycosis is endemic in Latin America.The infected cells show a typical "pilot's wheel" appearance due to multiple yeasts sprouting out of a single parent cell. Ref: Ray C.G., Ryan K.J. (2010). Chapter 46. Cryptococcus, Histoplasma, Coccidioides, and Other Systemic Fungal Pathogens. In C.G. Ray, K.J. Ryan (Eds), Sherris Medical Microbiology, 5e.