Lung - nontumor

Author: Elliot Weisenberg, M.D. (see Authors page)

Revised: 24 February 2017, last major update September 2011

Copyright: (c) 2003-2017,, Inc.

PubMed search: malakoplakia [title] pulmonary

Cite this page: Malakoplakia. website. Accessed October 16th, 2018.
Definition / general
  • Usually in urinary tract; very rare in lung, usually in immunocompromised patients
  • Caused by macrophage dysfunction involving intracellular lysosomal mediated killing of bacteria
  • In AIDS patients, usually due to Rhodococcus equi, an animal pathogen causing opportunistic infections (Chest 1999;115:889)
Case reports
  • Antibiotics
Gross description
  • Nodular masses or infiltrates with cavitation
Gross images

Images hosted on other servers:

Grayish white, ill
defined lesion with
central cavitation

Microscopic (histologic) description
  • Intraalveolar histiocytes with pink or foamy cytoplasm (von Hansemann’s histiocytes) that fill and destroy alveoli, not interstitium
  • Histiocytes contain PAS+ bacteria, also Michaelis-Gutmann bodies (round / oval structures, usually intracellular, 5 - 20 microns, with laminated or targetoid appearance that stain deeply with H&E, iron and calcium stains)
  • Also lymphocytes, plasma cells and neutrophils
Microscopic (histologic) images

Images hosted on other servers:

Various images

Differential diagnosis