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.
There may a predilection for the head and neck region or upper extremities 4.
Described features include patchy areas of hyperechogenicity, containing hypoechoic lines preservation of continuous muscle bundles.
- 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
Treatment and prognosis
Its clinical course is benign and local recurrence following simple excision is considered uncommon.
History and etymology
It was first described by H E Kern in 1960.
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