An unusual case of pleomorphic rhabdomyosarcoma of shoulder in an adult patient

Rhabdomyosarcoma (RMS) is a highly malignant soft tissue sarcoma (STS). It is the most common childhood STS and is exceedingly rare in adults. The pleomorphic subtype affecting patient older than 45 years is the least common subtype. It is histologically similar to a malignant fibrous histiocytoma. Many pleomorphic RMSs (PRMSs) have been reclassified as fibrous histiocytomas, thereby making the diagnosis of PRMS more unusual. Here, we report a case of PRMS in a 45-year-old male who reported with the painless soft tissue swelling over the posterior aspect of left shoulder for 1 year. Magnetic resonance (MR) imaging and MR angiography showed a large well defined heterogeneously enhancing soft tissue mass lesion arising from posterior fibers of left Deltoid muscle. The patient received nine cycles of neoadjuvant chemotherapy with ifosfamide, epirubicin every 3 weeks. The patient underwent wide local excision of the tumor and received four cycles of adjuvant chemotherapy ifosfamide, epirubicin, and etoposide every 3 weeks. Locoregional adjuvant radiotherapy 66 Gy in 33 fractions was given by 3-dimensional conformal radiotherapy. Now the patient has a complete response on follow-up imaging 2 years after completion of radiotherapy. PRMS in adults has a significantly worse prognosis than that for other pleomorphic sarcomas with 12.5–50% of 1-year to 20-month disease-free survival and 27% rate of 5-year disease free survival. Thus, the correct and early diagnosis of PRMS is important.