title: MYOD1 (L122R) mutations are associated with spindle cell and sclerosing rhabdomyosarcomas with aggressive clinical outcomes.
abstract: Recurrent mutations in the myogenic transcription factor MYOD1 and PIK3CA were initially described in a subset of embryonal rhabdomyosarcomas. Recently, two independent studies demonstrated presence of MYODI (L122R) mutations as the basis to re-classify a spindle cell rhabdomyosarcoma, along with a sclerosing rhabdomyosarcoma, distinct from an embryonal rhabdomyosarcoma. We analyzed a much larger cohort of 49 primary rhabdomyosarcoma tumor samples of various subtypes, collected over a period of 9 years, for the presence of MYOD1 (L122R), PIK3CA (H1047), and PIK3CA (E542/E545) mutations, along with immunohistochemical analysis of desmin, myogenin, and MYOD1. Although activating PIK3CA mutations were absent across the sample set analyzed, we report 20% MYOD1 (L122R) mutation in rhabdomyosarcomas, found exclusively in 10 of 21 spindle cell and sclerosing rhabdomyosarcomas, occurring mostly in the head and neck region along with extremity sites (64%), than the paratesticular and intra-abdominal sites. Furthermore, while all 10 MYOD1 mutant spindle cell and sclerosing rhabdomyosarcoma samples showed diffuse and strong MYOD1 immunoexpression, 7 of 31 samples of rhabdomyosarcoma with wild-type MYOD1 were negative for MYOD1 expression. Clinically, a striking correlation was found between MYOD1 mutation and the clinical outcomes available for 15 of 21 cases: 5 of 7 patients with spindle cell and sclerosing rhabdomyosarcomas, harboring MYOD1 mutation, were alive-with-disease and 2 of 8 patients with spindle cell and sclerosing rhabdomyosarcomas, with mutant MYOD1, were free-of-disease. Taken together, we present the first report of MYOD1 (L122R) mutation in the largest cohort of 49 rhabdomyosarcomas reported so far, that are associated with a relatively aggressive clinical course. Moreover, consistent with the earlier two studies, this study further reinforces a relationship between spindle cell and the sclerosing rhabdomyosarcoma-now recognized as a single subtype, distinct from an embryonal rhabdomyosarcoma.
authors: Department of Surgical Pathology, Tata Memorial Centre, Parel, Mumbai, Maharashtra, India.
authors: Bharat
authors: B
authors: Rekhi
authors: Integrated Genomics Laboratory, Advanced Centre for Treatment, Research and Education In Cancer, Tata Memorial Centre, Navi Mumbai, Maharashtra, India.|Homi Bhabha National Institute, Training School Complex Anushakti Nagar, Mumbai, India.
authors: Pawan
authors: P
authors: Upadhyay
authors: Integrated Genomics Laboratory, Advanced Centre for Treatment, Research and Education In Cancer, Tata Memorial Centre, Navi Mumbai, Maharashtra, India.
authors: Manoj P
authors: MP
authors: Ramteke
authors: Integrated Genomics Laboratory, Advanced Centre for Treatment, Research and Education In Cancer, Tata Memorial Centre, Navi Mumbai, Maharashtra, India.|Homi Bhabha National Institute, Training School Complex Anushakti Nagar, Mumbai, India.
authors: Amit
authors: A
authors: Dutt
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D017570:MyoD Protein / Q000235:genetics*; D012208:Rhabdomyosarcoma / Q000235:genetics* / Q000473:pathology; D055815:Young Adult
chemical_list: D014408:Biomarkers, Tumor; D017570:MyoD Protein; C057363:MyoD1 myogenic differentiation protein