Age / Sex : 61 / F

Chief complaint : Acute thigh pain


What is your diagnosis?


Two weeks later, you can see the final diagonosis with a brief discussion of this case (Please submit only one answer).



Courtesy : 박은혜 Eun Hae Park, 전북대학교병원 Chunbuk National University Hospital

Proliferative myositis

Discussion

Findings:

There is intramuscular mass like lesion. Typically this is muscle fiber preserving lesion. In follow up imaging there is decresed extent of lesion with less mass effect.

Differential Diagnosis:

Lymphoma

Heterotopic ossification

Inflammatory myopathy

Sarcoidosis

Discussion:

Proliferative myositis is within a spectrum of benign myofibroblastic tumor-like lesions. Thought to commonly occur in middle-aged adults (around 50 years), but has also been described in children. The key in diagnosing proliferative myositis lies in identifying the preserved continuous muscle bundles, which are a specific finding not described in other similar diagnoses or in soft tissue malignancies. It is justifiable to wait and monitor the lesion, since PM is a self-limiting proliferation and spontaneous recoveries have been described. Malignant transformation or metastases have not been reported.

References:

Arch Otolaryngol Head Neck Surg. 2008 Apr;134(4):437-40