Pleomorphic Rhabdomyosarcoma in Adults: A Clinicopathologic Study of 38 Cases with Emphasis on Morphologic Variants and Recent Skeletal Muscle-Specific Markers

Abstract

Pleomorphic rhabdomyosarcoma (PRMS) is a rare and controversial tumor of skeletal muscle phenotype. Diagnostic criteria for PRMS by combined histology and currently available immunohistochemistry have not been clearly defined. We report 38 pleomorphic rhabdomyosarcomas in adults, explore morphologic variants, and discuss our experience with both specific and nonspecific skeletal muscle markers in these tumors. Clinical data, morphology, and immunohistochemistry were reviewed. Electron microscopy was performed. Of 38 cases, there were 28 males and 10 females. Patient ages ranged from 21 to 81 years (median ‫؍‬ 54 y; mean ‫؍‬ 51 y). Tumors were located in the lower extremity (n ‫؍‬ 18), abdomen/retroperitoneum (n ‫؍‬ 6), chest/abdominal wall (n ‫؍‬ 5), spermatic cord/ testes (n ‫؍‬ 4), upper extremity (n ‫؍‬ 3), and one each in the mouth and orbit. Tumor sizes ranged from 1.5 to 15.0 cm (mean ‫؍‬ 7.3 cm; median ‫؍‬ 6.8 cm). The cases were divided into three variants, each with large, atypical, pleomorphic polygonal rhabdomyoblasts (PRMB) with abundant eosinophilic cytoplasm in varying numbers and different morphologic backgrounds of round or spindled rhabdomyoblasts (RMB). , fast skeletal muscle myosin, or myf4). In addition, all cases had some positivity for nonspecific muscle markers (desmin, MSA, SMA, myf3). Electron microscopy (EM), performed on eight selected cases from all three morphologic groups, demonstrated definitive skeletal muscle differentiation in all cases. Follow-up, available on 30 (79%) cases, revealed that 70% of patients died of disease (mean 20 months, range 1 month-108 months), 3% were alive with disease at 12 months (n ‫؍‬ 1); and 27% had no evidence of disease (mean, 83 mo; range, 18 to 108 mo). PRMS, a tumor of predominantly middle-aged adult males in the lower extremity, can be diagnosed by the morphologic presence of scattered PRMB with immunohistochemical evidence of at least one skeletal muscle-specific marker. There are three morphologic variants of PRMS. The appropriate diagnosis of PRMS is significant as it is a high-grade sarcoma, with an aggressive clinical course.

Head and Neck Rhabdomyosarcoma: Clinical and Pathologic Characterization of Seven Cases

“…ARMS occurs more frequently in adolescents, and exhibits more aggressive biological behavior [8]. PRMS occurs in both children and adults, but the outcome is significantly worse in adults, with higher rates of recurrence and metastasis [9,10]. Spindle cell RMS was traditionally included as a variant of ERMS but it is now provisionally listed as a separate spindle cell/sclerosing RMS subtype in the latest World Health Organization (WHO) classification (4th Edition, 2013).…”

Novel uses of immunohistochemistry in the diagnosis and classification of soft tissue tumors

“…3 Pleomorphic rhabdomyosarcoma and spindle cell/sclerosing rhabdomyosarcoma may show only limited myogenin expression in a small subset of cells. 4,5 MYOD1 (MYF3) is another skeletal muscle-specific transcription factor. Available antibodies may be more difficult to optimize than those directed against myogenin and sometimes show cytoplasmic background staining.…”

Rhabdomyosarcoma discovered in the adrenal region of an elderly hypertensive patient

“…In the pathological aspect, adult-type rhabdomyosarcomas are diagnosed according to morphologic criteria as well as positive immmunostaining for desmin and/or myoglobin, which are filamentous and oxidationrelated antigens. 2,4 Intranuclear transcription factors called myogenin and MyoD1 are also sensitive and specific markers for striated muscle differentiation and, as expressed in the present case, it is now well established that the positivity of one of these markers is necessary for diagnosis of rhabdomyosarcoma. [5][6][7] As for the prognosis, 2 25% of adult-type rhabdomyosarcoma patients died of cancer or therapeutic complications.…”