Mycobacterial Spindle Cell Pseudotumor

Mycobacterial Spindle Cell Pseudotumor

Tariq Muzzafar, MBBS

Mycobacterial spindle cell pseudotumor involving lymph node. Fascicles and storiform arrays of spindle cells efface nodal architecture.

Mycobacterial spindle cell pseudotumor involving lymph node. Fascicles of spindle cells and scattered small lymphocytes are present. Note bland-appearing nuclei and eosinophilic granularity of cytoplasm.



  • Tumor-like lesion composed of elongated spindle cells infected by Mycobacterium avium-intracellulare (MAI)


Infectious Agents

  • Mycobacterium aviumintracellulare

  • Cause of distinctive tumor-like appearance is unknown



  • Incidence

    • Rare entity; ˜ 20 cases reported in literature

    • Occur in immunocompromised patients

      • Particularly in those with acquired immunodeficiency syndrome (AIDS)

  • Age

    • Predominantly affects young individuals

  • Gender

    • Predominantly affects males


  • Lymph nodes most common

  • Other sites: Spleen, skin, bone marrow, lung, and brain

Laboratory Tests

  • Traditional media

    • Lowenstein-Jensen media

    • Agar-based Middlebrook medium

    • Growth of organisms is slow

      • Visible colony growth can take up to 6 weeks

  • Liquid media (growth takes ˜ 2 weeks)

    • BACTEC

    • Mycobacteria growth indicator tubes


  • Drugs

    • HIV(+): Clarithromycin or azithromycin + ethambutol

    • HIV(-): Clarithromycin or azithromycin plus rifampin or rifabutin and ethambutol


  • Anti-MAI drugs are effective, particularly if immunosuppression can be reversed


Radiographic Findings

  • Lymphadenopathy


Histologic Features

  • Lymph node architecture effaced by elongated spindle cells (histiocytes)

    • Arranged in short fascicles and storiform arrays

  • Histiocytes have bland nuclei, eosinophilic to granular cytoplasm

  • Admixed small lymphocytes

  • No significant mitotic activity

  • Acid-fast (Ziehl-Neelsen) stain demonstrates numerous bacilli within cells

Cytologic Features

  • In Wright-Giemsa touch imprints

    • Bland histiocytes

    • Negative outlines of MAI bacilli in cytoplasm

Jul 8, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Mycobacterial Spindle Cell Pseudotumor

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