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Abstract: Primary rhabdomyosarcoma of salivary glands is an extremely rare neoplasm, mostly seen in children. A newly described subtype of rhabdomyosarcoma, sclerosing rhabdomyosarcoma, has not yet been reported in this location. We report on a parotid gland tumor characterized by infiltrative growth of primitive type of neoplastic cells showing strong and diffuse nuclear positivity for MyoD1 and myogenin and by prominent hyalinized/chondroid matrix with some myxoid foci. The tumor recurred several times, and in recurrent tumors, differentiation into strap myoid cells appeared. There were no distant metastases during the 5-year follow-up. Sclerosing rhabdomyosarcoma may cause differential diagnostic problems because it could be confounded for osteosarcoma, chondrosarcoma, and some other types of sarcoma, and as in our case, for myxofibrosarcoma and myoepithelial carcinoma. Its location in the head and neck is of special interest because 6 of 14 previously described adult cases of sclerosing rhabdomyosarcoma and 7 of 18 pediatric cases also occurred in this region. To our knowledge, this is the first reported case of primary sclerosing rhabdomyosarcoma of the parotid gland. [Copyright &y& Elsevier]

Summary: Since the first description of sclerosing rhabdomyosarcoma in 2000, 19 pediatric cases have been reported in the literature. However, it is debated whether sclerosing rhabdomyosarcoma represents a specific rhabdomyosarcoma entity or a variant of embryonal or alveolar rhabdomyosarcoma. To date, 6 sclerosing rhabdomyosarcoma karyotypes and 1 sclerosing rhabdomyosarcoma comparative genomic hybridization profile have been reported. We present the first whole-genome tumoral genotyping of a sclerosing rhabdomyosarcoma by high-density single nucleotide polymorphism array. The single nucleotide polymorphism genotyping revealed a complex pattern including gains and losses of whole chromosomes and an amplification of the 12q13-15 region. Amplification of the 12q13-q15 region containing SAS, GLI, CDK4, and MDM2 has been observed in rhabdomyosarcoma. In the present case, the 2 amplified target genes were MDM2 and HMGA2, excluding CDK4. The identification of a specific MDM2-HGMA2 amplicon excluding CDK4 has only been described so far in well-differentiated and dedifferentiated liposarcoma. Further studies are needed to assess if this anomaly is a specific marker of sclerosing rhabdomyosarcoma. [Copyright &y& Elsevier]