Aggressive rhabdomyosarcoma tumors that harboring MYOD1 mutations

Clinical collaborator: Dr. Bharat Rekhi (TMH)

The uncommonness of rhabdomyosarcoma (RMS) cancer lends itself to the need for further research. Two recent studies demonstrated presence of MYODI (L122R) mutations as the basis to re-classify spindle cell RMS along with sclerosing RMS, distinct from ERMS subtype. Here, we have analyzed a cohort of 49 rare primary RMS tumor samples of various subtypes, collected over a period of 9 years, for presence of MYOD1 (L122R), PIK3CA (H1047) and PIK3CA (E542/E545) mutations, along with immunohistochemical analysis of desmin, myogenin and MYOD1, and clinical outcome.

We report 20.4% MYOD1 (L122R) mutation in RMS, found exclusively in spindle cell/sclerosing RMS subtype tumor. Moreover, a striking correlation was found between MYOD1 mutation and clinical outcomes. Based on these findings, MYOD1 (L122R) mutation may preclude the requirement to perform IHC analysis to identify an aggressive subset of spindle cell/sclerosing RMS patients early on to help inform adoption of appropriate therapeutic regimen. In over all, we present the first report of MYOD1 (L122R) mutation in a large cohort of 49 RMS reported so far, as a single study, that are associated with a relatively aggressive clinical course.

[ Immunohistochemical and mutational analysis of 49 cases of Rhabdomyosarcomas. ]
[MODERN PATHOLOGY]