Proliferative myositis

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

Epidemiology

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

Clinical presentation

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

Pathology

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.

Radiographic features

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
T1 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 1960⁶.

-<p><strong>Proliferative myositis (PM) </strong>is a rare benign <a href="/articles/inflammatory-myopathy">inflammatory myopathy</a>. It is sometimes classified as a subtype of a <a href="/articles/pseudosarcomatous-proliferative-soft-tissue-lesion">pseudosarcomatous proliferative soft-tissue lesion</a>.</p><h4>Epidemiology</h4><p>Thought to commonly occur in middle-aged adults (around 50 years), but has also been described in children.</p><h4>Clinical presentation</h4><p>Patients may present with a rapidly enlarging solitary, firm and painful soft-tissue mass.</p><h4>Pathology</h4><p>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.</p><h5>Location</h5><p>There may a predilection for the head and neck region or upper extremities <sup>4</sup>.</p><h4>Radiographic features</h4><h5>Ultrasound</h5><p>Described features include patchy areas of hyperechogenicity, containing hypoechoic lines preservation of continuous muscle bundles.</p><h5>MRI</h5><ul>
+<p><strong>Proliferative myositis (PM) </strong>is a rare benign <a href="/articles/inflammatory-myopathy">inflammatory myopathy</a>. It is sometimes classified as a subtype of a <a href="/articles/pseudosarcomatous-proliferative-soft-tissue-lesion">pseudosarcomatous proliferative soft-tissue lesion</a>.</p><h4>Epidemiology</h4><p>Thought to commonly occur in middle-aged adults (around 50 years), but has also been described in children.</p><h4>Clinical presentation</h4><p>Patients may present with a rapidly enlarging solitary, firm and painful soft-tissue mass.</p><h4>Pathology</h4><p>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.</p><h5>Location</h5><p>There may a predilection for the head and neck region or upper extremities <sup>4</sup>.</p><h4>Radiographic features</h4><h5>Ultrasound</h5><p>Described features include patchy areas of hyperechogenicity, containing hypoechoic lines preservation of continuous muscle bundles.</p><h5>MRI</h5><ul>
~~-<strong>C (Gd): </strong>there may be subtotal enhancement with non-enhancing geometrical web and fascial enhancement sometimes been described <sup>2</sup>~~
+<strong>T1 C+ (Gd): </strong>there may be subtotal enhancement with non-enhancing geometrical web and fascial enhancement sometimes been described <sup>2</sup>
-</ul><h4>Treatment and prognosis</h4><p>Its clinical course is benign and local recurrence following simple excision is considered uncommon.</p><h4>History and etymology</h4><p>It was first described by <strong>H E Kern</strong> in 1960.</p><h4>See also</h4><ul><li><a href="/articles/soft-tissue-tumours-classification-who-2002">WHO 2002 soft tissue tumour classification system</a></li></ul>
+</ul><h4>Treatment and prognosis</h4><p>Its clinical course is benign and local recurrence following simple excision is considered uncommon.</p><h4>History and etymology</h4><p>It was first described by <strong>H E Kern</strong> in 1960 <sup>6</sup>.</p><h4>See also</h4><ul><li><a href="/articles/soft-tissue-tumours-who-2002-classification">WHO 2002 soft tissue tumour classification system</a></li></ul>

References changed:

6. Kern WH. Proliferative myositis; a pseudosarcomatous reaction to injury: a report of seven cases. (1960) Archives of pathology. 69: 209-16. <a href="https://www.ncbi.nlm.nih.gov/pubmed/14408614">Pubmed</a> <span class="ref_v4"></span>

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