Malakoplakia

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ΕΤΥΜΟΛΟΓΙΑ

From Greek. Malakos meaning soft and plakos meaning plaque. Drs Michaelis and Gutmann were the authors of the original publication, although it was Professor von Hansemann who described the first human case having read about a similar veterinary in 1900. Professor von Hansemann introduced the topic to Dr Gutmann, who was his assistant at the time, for further investigation in collaboration with Dr Michaelis, a biochemist.[1][2]
Granulomatous inflammatory condition thought to result from defective phagolysosomal clearance of bacteria following phagocytosis. Malakoplakia usually affects the urinary tract and kidneys, but is also described in the gallbladder and prostate and may present in other body sites. The significance of malakoplakia is that it may be a mimic of malignancy.

Histological Features

Numerous von Hansemann histiocytes are visible mainly in the upper half of this photomicrograph. Targetoid Michaelis-Gutmann bodies are also present.
von Kossa stain showing numerous Michaelis-Gutmann bodies - more than apparent on H&E staining.

The histiocytes seen in malakoplakia are called von Hansemann histiocytes and have abundant eosinophilic, granular cytoplasm. Michaelis-Gutmann (MG) bodies are basophilic, targetoid, intra-cytoplasmic bodies and are the main, but not obligatory, diagnostic feature of malakoplakia. They are thought to represent the result of bacteria-laden phagolysosomes that have had calcium pumped into them. The calcium is thought to precipitate with phosphate-containing components of the bacterial wall. MG bodies stain positively with von Kossa (for calcium) and Perls' staining (for iron).

References

  1. Michaelis L & Gutmann D. Ueber Einschlüsse in Blasentumoren. Zeitschrift für klinische Medizin 1902;47:208
  2. Dasgupta P, Womack C, Turner AG, Blackford HN. Malacoplakia: von Hansemann's disease. BJU international. 1999 Sep; 84(4):464-9.