[1671] Atypical Mycobacterial Brain Abscess Presenting as Spindle Cell Lesion in an Immunocompetent Patient

K Arkun, DA Gordon, C Lincoln, M Levi, J Bello, CE Keller, KM Weidenheim. Montefiore Medical Center, Bronx, NY; Albert Einstein College of Medicine, Bronx, NY

Background: Mycobacterium Avium Complex (MAC) organisms are important secondary infections in immunocompromised patients and are usually seen in patients with AIDS. Disseminated and focal MAC infections usually involve the lungs, gastrointestinal tract and peripheral lymph nodes. It is unusual to see involvement of the central nervous system, where MAC produces imaging findings similar to tuberculoma.
Design: We present a 52-year-old HIV-negative man with a previous history of non-caseating pulmonary granulomata and lung carcinoma treated with radiotherapy, who presented with 6 month history of slowly progressive dizziness, headache,and gait disturbance with frequent falls. Tissue obtained at subtotal resection was cultured and paraffin sections were examined with the light microscope.
Results: Neuroimaging revealed a large, complex, multiloculated, ring-enhancing cystic lesion centered in the left tentorium with extension into supratentorial and infratentorial compartments. Compression of the fourth ventricle resulted in hydrocephalus that required subtotal resection of the mass and aspiration of caseous yellow material. The specimen consisted of a variably cellular proliferation of CD68-positive spindle cells arranged in bands, fascicles and ill-defined nodules. A few lymphocytes and plasma cells were seen, and a single giant cell was present. Delicate rod-shaped organisms were faintly positive using methenamine silver, Brown-Brenn Gram staining and Ziehl-Neelsen staining. The bacilli were strongly positive with Fite and Kinyoun staining, and DNA probes confirmed their identification as MAC. M. tuberculosis was not present on DNA analysis.
Conclusions: This MAC brain abscess presented as a complex mass with differential diagnosis that includes infections and tumor. Its exuberant spindle cell proliferation had a pseudosarcomatous appearance and produced difficulty in diagnosis because granulomatous features were found only focally. Clinical correlation and culture results were critical in obtaining the correct diagnosis. In the appropriate clinical setting, infectious processes including MAC-related brain abscess, should be ruled out before making the diagnosis of a spindle cell neoplasm.
Category: Neuropathology

Tuesday, March 23, 2010 1:00 PM

Poster Session IV # 244, Tuesday Afternoon


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