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myositis ossificans

Monday 27 April 2009


- 57 yr old female - thigh - history of fracture femur 2 months back: Myositis Ossificans

Digital cases

- UI:638 - Myositis ossificans (or soft tissue osteoma?)


- myositis ossificans circumscripta

  • myositis ossificans circumscripta is a benign lesion characterized by focal heterotopic soft tissue ossification, occurring in young people generally after localized trauma. Clinical and radiological appearances may mimic a sarcomatous neoplastic process.

Nota bene: Myositis ossificans and fibro-osseous pseudotumour are now regarded as variants of nodular fasciitis.


- male predominance
- active fibroblastic proliferation
- fibroblastic/myofibroblastic proliferation closely resembling nodular fasciitis
- transition from proliferating spindle-shaped cells to trabeculae of osteoid lined by plump osteoblasts
- Osteoblast-lined osteoid adjacent to spindle cell proliferation resembling nodular fasciitis
- Numerous osteoblasts are seen lining osteoid, surrounded by a cytologically bland proliferation of spindle-shaped cells.
- zone of osteoid trabeculae rimmed by osteoblasts, underneath which is a proliferation of spindle-shaped cells.
- fibrin deposits with metaplasia leading to the formation of an unusual osteoid.

Fine needle aspiration cytology

The FNAC smear of MO shows fibroblasts, osteoblasts, multinucleated giant cells, degenerated muscle cells and osteoid.


- Fine needle aspiration cytology of myositis ossificans. Barwad A, Banik T, Gorsi U, Dey P. Diagn Cytopathol. 2011 Jun;39(6):432-4. PMID: 20954272

- Amendola MA, Glazer GM, Agha FP, Francis IR, Weatherbee L. Myositis ossificans circumscripta: computed tomographic diagnosis. Radiology 1983;149:775-9.

- Pseudomalignant myositis ossificans. A pathological study of eight cases. Lagier R, Cox JN. Hum Pathol. 1975 Nov;6(6):653-65. PMID: 1183991