Hematoxylin-eosin–stained sections of the tissue specimen showed hyperkeratosis and acanthosis, with no evidence of infection or neoplasia. Gram and acid-fast bacillus stains and fungal cultures of the exudate were negative for organisms. Culture of the tissue yielded slow-growing, golden-yellow, atypical mycobacteria that were positive for acid-fast bacilli. Acid-fast bacillus stains and fungal cultures of bone marrow and blood samples were negative for organisms. Chest x-ray films revealed new scarring in the right upper lobe, which might have been the source of the mycobacteria or the result of radiation therapy or pneumonia.
Red Nodule on the Finger of an Immunosuppressed Woman. Arch Dermatol. 2002;138(5):689-694. doi:10.1001/archderm.138.5.689