Proliferative myositis

Proliferative myositis (PM) is a rare benign inflammatory myopathy. It is sometimes classified as a subtype of a pseudosarcomatous proliferative soft-tissue lesion.

Thought to commonly occur in middle-aged adults (around 50 years), but has also been described in children.

Patients may present with a rapidly enlarging solitary, firm and painful soft-tissue mass.

It is characterized by infiltration of basophilic giant cells and proliferative fibroblasts within the affected region. Its exact aetiology is not well known although an antecedent recent local trauma has been documented in some cases.

Location

There may a predilection for the head and neck region or upper extremities 4.

Ultrasound

Described features include patchy areas of hyperechogenicity, containing hypoechoic lines preservation of continuous muscle bundles.

MRI
  • T2: may show an ill-defined, hyperintense, intramuscular lesion, containing isointense lines 2
  • C (Gd): there may be subtotal enhancement with non-enhancing geometrical web and fascial enhancement sometimes been described 2

Its clinical course is benign and local recurrence following simple excision is considered uncommon.

It was first described by H E Kern in 1960.

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Article Information

rID: 35722
Section: Pathology
Synonyms or Alternate Spellings:
  • Proliferative myositis (PM)

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