title: Cutaneous mycobacterial spindle cell pseudotumor: a potential mimic of soft tissue neoplasms.
abstract: A 55-year-old man with scleroderma treated with prednisone and etanercept presented with enlarging sporotrichoid nodules on the forearm. Microscopically, there were large circumscribed dermal and subcutaneous nodules of spindled and epithelioid cells, resembling a spindle cell neoplasm. Small foci of neutrophils were also present, and a subsequent Ziehl-Neelsen stain highlighted beaded acid-fast bacilli in the interstitium. Tissue culture demonstrated Mycobacterium chelonae. Cutaneous mycobacterial spindle cell pseudotumor is an exceedingly rare lesion, with only 6 previously reported cases. Although these included patients with autoimmune disease receiving immunosuppressive therapy, this is the first case reported in association with a tumor necrosis factor alpha inhibitor, etanercept. Furthermore, this represents the first mycobacterial spindle cell pseudotumor described in association with M. chelonae. Mycobacterial spindle cell pseudotumor should be considered in the differential diagnosis of cutaneous spindle cell proliferations, especially in immunocompromised patients.
authors.affiliation: Department of Pathology, University of California, San Francisco, 94115, USA. iwei.yeh@gmail.com
authors.forename: Iwei
authors.initials: I
authors.lastname: Yeh
authors.forename: George
authors.initials: G
authors.lastname: Evan
authors.forename: Chris H
authors.initials: CH
authors.lastname: Jokinen
mesh_terms: D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D017291:Clarithromycin / Q000627:therapeutic use; D003937:Diagnosis, Differential; D000068800:Etanercept; D006104:Granuloma, Plasma Cell / Q000175:diagnosis* / Q000188:drug therapy / Q000382:microbiology; D006801:Humans; D016867:Immunocompromised Host; D007074:Immunoglobulin G / Q000627:therapeutic use; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D009165:Mycobacterium Infections, Nontuberculous / Q000175:diagnosis* / Q000188:drug therapy / Q000382:microbiology; D016926:Mycobacterium chelonae / Q000302:isolation & purification; D011241:Prednisone / Q000627:therapeutic use; D018124:Receptors, Tumor Necrosis Factor / Q000627:therapeutic use; D012509:Sarcoma / Q000175:diagnosis*; D012595:Scleroderma, Systemic / Q000150:complications* / Q000188:drug therapy / Q000276:immunology; D012871:Skin Diseases / Q000175:diagnosis* / Q000188:drug therapy / Q000382:microbiology; D012983:Soft Tissue Neoplasms / Q000175:diagnosis*
chemical_list: D000900:Anti-Bacterial Agents; D007074:Immunoglobulin G; D007166:Immunosuppressive Agents; D018124:Receptors, Tumor Necrosis Factor; D017291:Clarithromycin; D000068800:Etanercept; D011241:Prednisone