Spindle cell (leiomyomatous) rhabdomyosarcoma, a rare variant of embryonal rhabdomyosarcoma

Fusion-driven Spindle Cell Rhabdomyosarcomas of Bone and Soft Tissue: A Clinicopathologic and Molecular Genetic Study of 25 Cases

The evolving classification of rhabdomyosarcoma (RMS) now includes spindle cell RMS (SRMS). Bone/soft tissue SRMS often harbor TFCP2, or less often MEIS1 rearrangements. We studied 25 fusion-driven SRMS involving bone (n = 19) and soft tissue (n = 6). Osseous SRMS occurred in 13 women and 6 men (median age: 41 years) and involved the pelvis (5), sacrum (2), spine (4), maxilla (4), mandible (1), skull (1), and femur (2). Follow-up (median: 5 months) demonstrated local recurrence in 2/16 and distant metastases in 8/17 patients (median time to metastasis: 1 month). Eight patients died of disease; 9 were alive with disease. Soft tissue SRMS occurred in 4 men and 2 women (median: 50 years). Follow-up (median: 10 months) revealed distant metastasis at diagnosis (1), alive with unresected tumor (1), and no evidence of disease (4). Next-generation sequencing demonstrated FUS::TFCP2 (12), EWSR1::TFCP2 (3) and MEIS1::NCOA2 (2); FISH identified EWSR1 (2) rearrangements. Most TFCP2-rearranged SRMS (13/17) showed spindled/epithelioid morphology, rarely with rhabdomyoblasts. The bone tumors were diffusely desmin and MyoD1 positive with limited myogenin; 10/13 were ALK -positive and 6/15 were keratin positive. Soft tissue SRMS harbored EWSR1::TFCP2, MEIS1::NCOA2, ZFP64::NCOA2, MEIS1::FOXO1, TCF12::VGLL3 and DCTN1::ALK, and displayed spindled/epithelioid, leiomyomatous, and myxofibrosarcoma-like morphologies. Immunohistochemistry (IHC) was positive for MyoD1 (6/6), focal desmin (5/6), myogenin (3/6), and keratin (1/6). We conclude that TFCP2-rearranged SRMS of bone and soft tissue show consistent morphologic and IHC features, likely representing a distinct subset of RMS. Non-TFCP2 fusion-positive SRMS could represent a single RMS subset, multiple subtypes of RMS, or "fusion-defined" sarcomas with rhabdomyoblastic differentiation.

Paratesticular Pleomorphic Rhabdomyosarcoma in the Elderly

A case of paratesticular pleomorphic rhabdomyosarcoma, presenting as an ulcerated mass in the left hemiscrotum of an 83-year-old man, is reported. By light microscopy, this neoplasm could not be distinguished from other pleomorphic sarcomas, such as malignant fibrous histiocytoma, leiomyosarcoma, and liposarcoma. Immunohistochemistry showed that most tumor cells were strongly reactive with antibodies directed against myoglobin, desmin, a-sarcomeric actin, and myogenin, whereas x-smooth muscle actin expression was less extensive. Electron microscopic examination demonstrated thick and thin filaments with condensations of electron-dense material reminiscent of structures of Z-lines in the large pleomorphic cells. On the basis of these findings, the neoplasm was classified as a pleomorphic rhabdomyosarcoma. According to a review of the literature, this is the first well-documented example of paratesticular pleomorphic rhabdomyosarcoma in an elderly person.

Pleomorphic rhabdomyosarcoma showing smooth-muscle and fibrohistiocytic differentiation: a single case report

Rhabdomyosarcoma has traditionally been subclassified into alveolar, embryonal, and pleomorphic variants. Less commonly, spindle-cell, neuroendocrine, sclerosing, and lipid-rich or clear-cell subtypes are seen. The author recently encountered a myogenic sarcoma, with all the common markers of rhabdomyosarcoma, but expressing the unusual features of alpha-smooth-muscle actin and abundant rough endoplasmic reticulum (rER). This myogenic sarcoma, therefore, exhibited four lines of differentiation, and is documented here. The patient was a 65-year-old man with an inguinal soft tissue mass. Following surgical excision, the patient was given radiotherapy and was well without disease after 6 years. The tumor was positive for vimentin, desmin, alpha-smooth-muscle actin, alpha-sarcomeric actin, myogenin, MyoD1, and CD68. Cytoplasm was dominated by abundant rER intermingled with lipid droplets and lysosomes. Cell surfaces exhibited microvillous processes and focal adhesions, but no lamina. Subplasmalemmal smooth-muscle-type myofilaments with focal densities and rare sarcomeric filaments were seen. The low level of expression of some markers was interpreted as consistent with a poorly differentiated tumor. Given the four lines of differentiation--striated muscle, smooth muscle, fibroblastic, and histiocytic--a name reflecting its phenotype would be pleomorphic rhabdomyosarcoma showing smooth-muscle and fibrohistiocytic differentiation.

Spindle cell rhabdomyosarcoma in adults. A case report and literature review

Spindle cell rhabdomyosarcoma, a recently described variant of embryonal rhabdomyosarcoma in children, carries a favorable prognosis when compared with other types of rhabdomyosarcoma. This tumor is rare in adults, and only four cases have been documented previously. The clinicopathological study of such a case occurring in the retroperitoneal space of a 53-year-old man is herein reported. The patient died of uncontrolled local recurrence and hepatic metastases seven months after diagnosis. Based on the analysis of the data of the five cases reported, including the present one, it can be stated that spindle cell rhabdomyosarcoma in adults is not associated with the favorable outcome observed in the pediatric population.

Orbital rhabdomyosarcomas and related tumors in childhood: relationship of morphology to prognosis--an Intergroup Rhabdomyosarcoma study

Children and adolescents who develop rhabdomyosarcoma (RMS) and related sarcomas in the orbit and treated on Intergroup Rhabdomyosarcoma protocols have had an extremely high cure rate. This study evaluates the possible relationship between their tumor morphologic subtypes and this high cure rate. The histology of tumors was re-reviewed from 229 of the 264 patients with tumors of the orbit, conjunctiva, and eyelids treated on Intergroup Rhabdomyosarcoma Studies (IRS I, II, III, and IV pilot protocols, and followed through July, 1992. Immunohistochemistry was applied in selected cases. Clinical correlations were done on all 264 cases including both the re-reviewed cases and those reviewed only by the IRS Pathology committee. The 5-year survival rate of 24 children with alveolar RMS was 74% (p < .001). All five infants diagnosed to have an alveolar RMS died before the age of one. Two hundred and twenty-one patients (84%) had embryonal RMS. About three-fourths of the re-reviewed embryonal RMS tumors showed only minimal rhabdomyoblastic differentiation. Thirty-one had a spindle cell RMS, two were anaplastic variants. The 5-year survival rate for patients with embryonal RMS subtypes combined was 94%, and 97% for the 144 patients with poorly differentiated embryonal RMS. In contrast, 90 of 432 IRS II patients treated for poorly differentiated embryonal RMS located in extraocular sites had a 66% survival estimate.