Rhabdomyosarcoma with Bone Marrow Infiltration: A Diagnostic Dilemma

Rhabdomyosarcoma is the most common soft tissue sarcoma in children and adolescents. In adults, the prevalence is much lower. Most patients present with a mass in the head and neck region, urogenital region or even with distal extremity involvement. A bone marrow infiltration at the time of clinical presentation has also been documented in literature. But a simultaneous marrow infiltration can simulate a hematopoietic neoplasm, leading to diagnostic errors. We document one such challenging case of a 47 year old male patient presenting with bicytopenia. Patient was hospitalized following a referral due to a mass in the left cheek, diagnosed earlier as clear cell sarcoma. Bone marrow aspirates yielded a dry tap, with sinusoidal blood and both the aspirate as well as the imprint smear showed pleomorphic cells with vacuolated cytoplasm. The corresponding trephine biopsy showed diffuse and interstitial infiltrates of rhabdoid cells with focal areas of infarct. Considering the morphological details, a diagnosis of rhabdomyosarcoma was rendered after ruling out other possibilities. A review of the lesional biopsy with ancillary techniques eventually corroborated the bone marrow diagnosis.