Liou J.-H.Huang P.-Y.CHIEN-CHING HUNGHsiao C.-H.2021-12-012021-12-0120030929-6646https://www.scopus.com/inward/record.uri?eid=2-s2.0-0141427899&partnerID=40&md5=934b53c33d03c082186e2d733e221517https://scholars.lib.ntu.edu.tw/handle/123456789/588999Spindle cell pseudotumors may occur due to mycobacterial infection in immunocompromised hosts, particularly those with acquired immunodeficiency syndrome (AIDS). Most of the reported mycobacterial spindle cell pseudotumors were found in the lymph nodes. We report a case of spindle cell pseudotumor in a 37-year-old man with AIDS who presented with a firm nodule over his right arm. Histologically, the tumor was composed of proliferative spindle cells admixed with histiocytes and inflammatory cells. Ziehl-Neelsen stain revealed many acid-fast bacilli in the spindle cells and histiocytes. The acid-fast bacilli were shown to be Mycobacterium avium intracellulare by culture and sequencing of the polymerase chain reaction product of mycobacterial 65-kDa heat shock protein gene. Immunohistochemically, the spindle cells were reactive to CD68, suggesting macrophage differentiation of these cells. It is important for pathologists to recognize this unusual manifestation of mycobacterial infection in immunocompromised patients and avoid mistaking the lesion for a mesenchymal neoplasm.AIDS-related opportunistic infection; Mycobacteria, atypical; Review; Skin diseases, bacterial[SDGs]SDG3CD68 antigen; heat shock protein; acid fast bacterium; acquired immune deficiency syndrome; adult; article; bacterium culture; case report; cell differentiation; cell proliferation; gene sequence; histiocyte; histopathology; human; immune deficiency; immunohistochemistry; immunoreactivity; inflammatory cell; lymph node; macrophage; male; mycobacteriosis; Mycobacterium intracellulare avium; pathologist; polymerase chain reaction; pseudotumor; skin nodule; skin tumor; spindle cell; staining; tumor localization; Adult; AIDS-Related Opportunistic Infections; Diagnosis, Differential; Humans; Male; Mycobacterium avium Complex; Mycobacterium avium-intracellulare Infection; Skin Diseasesjournal article128746752-s2.0-0141427899