Short review of inflammatory rhabdomyoblastic tumor: A newly described entity that does not fit into the current classification of skeletal muscle neoplasms

Abstract

Inflammatory rhabdomyoblastic tumor (IRMT), previously called histiocyte-rich rhabdomyoblastic tumor (HRRMT), is a recently described skeletal muscle neoplasm of uncertain malignant potential, commonly affecting young-to-middle aged men, typically arises in the skeletal muscles of the lower extremities and trunk and mostly has an intermediate (rarely metastasizing) clinical behavior. IRMT/HRRMT is commonly characterized by slow growth and encapsulation containing lymphoid aggregates. It is composed of spindle-to-epithelioid cells with a rhabdomyoblastic immunophenotype, a diffuse histiocytic infiltrate, and low mitotic figures. In this review, we will summarize its clinicopathologic features, immunophenotypic and molecular findings, prognosis, and treatment based on currently available published case reports. The purpose of this review is to increase awareness of this rare entity among pathologists and further help clinicians to manage patients properly.

Keywords

• Rhabdomyoblastic tumor
• Histiocyte-rich
• Inflammatory
• MyoD1
• Myogenin