Rhabdomyosarcoma with Pseudolipoblasts Arising in Ovarian Carcinosarcoma: A Distinctive Postchemotherapy Morphologic Variant Mimicking Pleomorphic Liposarcoma

Abstract

We describe a case of ovarian carcinosarcoma occurring in a 60-year-old female. The neoplasm was excised after neoadjuvant chemotherapy and contained a predominant heterologous pleomorphic rhabdomyosarcomatous component in which there were numerous multivacuolated rhabdomyoblasts that strongly mimicked lipoblasts. The clear cell variant of rhabdomyosarcoma is rarely documented, but this case shows a highly unusual finding in which the rhabdomyoblasts show the prominent multivacuolation with nuclear indentation characteristic of and indistinguishable from pleomorphic lipoblasts. This appears to represent a posttreatment phenomenon. As this finding might conceivably occur in other rhabdomyosarcomas after chemotherapy, we highlight the potential for diagnostic confusion with pleomorphic liposarcoma, which is usually diagnosed by morphology so that immunohistochemistry for muscle markers might not be performed.

Adipocyte-Like Differentiation in a Posttreatment Embryonal Rhabdomyosarcoma

“…Coffin et al described the presence of vacuolated cells in a rhabdomyosarcoma [ 9 ]. Likewise, a case report of an ovarian carcinosarcoma with pleomorphic rhabdomyosarcomatous differentiation noted the presence of “pseudolipoblasts” after neoadjuvant chemotherapy [ 5 ]. The presence of cells with morphology intermediate between rhabdomyoblasts and multivacuolated adipocyte-like cells suggested that the chemotherapy induced differentiation in the rhabdomyosarcomatous component of the carcinosarcoma, representative of a posttreatment phenomenon [ 5 ].…”

“…So-called “cytodifferentiation” after neoadjuvant chemotherapy is a well-described phenomenon in rhabdomyosarcoma and consists of more prominent rhabdomyoblasts and decreased primitive, proliferating cells [ 2 – 4 ]. Rhabdomyosarcoma with adipocyte-like cells has been rarely observed in unusual ovarian carcinosarcomas [ 5 ]. However, to our knowledge, the present case represents the first example of a soft tissue rhabdomyosarcoma with adipocyte-like cells after chemotherapy.…”