Mycobacterial spindle cell pseudotumor of the skin.
BACKGROUND
Mycobacterial spindle cell pseudotumor is a rare tumor-like lesion characterized by the proliferation of spindle cells engorged with mycobacterial microorganisms. To our knowledge, only a few cases of cutaneous lesions have been described in the literature.


METHODS
A 58-year-old Japanese woman presented with a nodule in her left forearm. She had systemic lupus erythematosus and interstitial pneumonia for 17 years, treated with prednisolone and azathioprine. She was also receiving insulin treatment for diabetes mellitus.


RESULTS
Histologically, the lesion was located in the deep dermis with extension into the subcutaneous fat tissue and was composed mainly of spindle cells focally showing a vaguely storiform pattern. In limited focal areas, foam cells, epithelioid histiocytes, and multinucleated giant cells were seen sparsely. Ziehl-Neelsen staining showed numerous acid-fast bacilli within the spindle cells and epithelioid histiocytes. The acid-fast bacilli were determined by culture and polymerase chain reaction to be Mycobacterium intracellulare.


CONCLUSIONS
We emphasize that mycobacterial spindle cell pseudotumor should be included in the differential diagnoses of a spindle cell lesion in the skin, especially in immunosuppressed patients.
Shiomi
Tatsushi
T
Laboratory of Diagnostic Pathology, Kyoto University Hospital, Sakyo-ku, Kyoto, Japan. shio@kuhp.kyoto-u.ac.jp
Yamamoto
Tetsurou
T
Manabe
Toshiaki
T
D000893:Anti-Inflammatory Agents / Q000627:therapeutic use; D003920:Diabetes Mellitus; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D017563:Lung Diseases, Interstitial / Q000150:complications / Q000188:drug therapy; D008180:Lupus Erythematosus, Systemic / Q000150:complications / Q000188:drug therapy; D008875:Middle Aged; D015270:Mycobacterium avium-intracellulare Infection / Q000150:complications / Q000378:metabolism / Q000473:pathology*; D011239:Prednisolone / Q000627:therapeutic use; D012509:Sarcoma / Q000473:pathology*; D012878:Skin Neoplasms / Q000150:complications / Q000382:microbiology* / Q000473:pathology*
D000893:Anti-Inflammatory Agents; D011239:Prednisolone