Pseudotumor resulting from atypical mycobacterial infection: a "histoid" variety of Mycobacterium avium-intracellulare complex infection.

A 54-year-old immunosuppressed cardiac transplant recipient with a six-month history of progressive swelling of the hand, with nodules and linear lymph node chain enlargement, diagnosed as a sporotrichoid Mycobacterium avium-intracellulare pseudotumor is described. The microscopic features closely resembled the previously described histoid variety of lepromatous leprosy. Routine hematoxylin and eosin staining suggested a spindle cell neoplasm rather than an infectious or inflammatory process. An infectious etiology was pursued on the basis of the clinical setting.