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The histogenesis of the rare primary cutaneous epithelioid rhabdomyosarcoma (PCERMS) remains unclear, with the morphological and immunophenotypic appearance of a rhabdomyosarcoma but a genomic profile consistent with sarcomatoid undifferentiated malignant melanoma (SUMM). Here, we provide comprehensive clinical, histopathological, and genomic analysis of a putative PCERMS presenting in an elderly patient. Histopathologic examination revealed an ulcerative tumefactive lesion with diffuse replacement of the dermis by sheets of malignant epithelioid cells with a rhabdoid appearance. By immunohistochemistry, the tumor cells were strongly and diffusely positive for desmin and myogenin. Comprehensive genomic analysis with a 542 gene DNA-based sequencing panel revealed likely biallelic NF1 inactivation (mutation and deletion), TERT promoter mutation, and a high tumor mutation burden (>100 mutations/mB) with features of a UV-mutational signature, which are all genomic features that can be seen in undifferentiated malignant melanoma. This case provides evidence of a close relationship at a molecular level between PCERMS and SUMM. Molecular genomic characterization of a larger cohort of PCERMS is warranted for further elucidation., (© 2023 The Authors. Genes, Chromosomes and Cancer published by Wiley Periodicals LLC.)

Cytomegalovirus (CMV) has been detected in several human cancers, but it has not proven to be oncogenic. However, recent studies have suggested mechanisms through which cytomegalovirus may modulate the tumor environment, encouraging its study as a positive modifier of tumorigenesis. In this study, we investigated the effects of cytomegalovirus infection in Trp53 heterozygous mice. Animals were infected with murine cytomegalovirus (MCMV) after birth at 2 days (P2) or 4 weeks of age and then monitored for tumor formation. Mice injected at 2 days of age developed tumors at a high frequency (43%) by 9 months of age. In contrast, only 3% of mock-infected or mice infected at 4 weeks developed tumors. The majority of tumors from P2 MCMV-infected mice were pleomorphic rhabdomyosarcomas (RMS) harboring MCMV DNA, RNA, and protein. An examination of clinical cases revealed that human RMS (embryonal, alveolar, and pleomorphic) harbored human cytomegalovirus IE1 and pp65 protein as well as viral RNA. Taken together, our findings offer support for the hypothesis that cytomegalovirus contributes to the development of pleomorphic RMS in the context of Trp53 mutation, a situation that occurs with high frequency in human RMS., (©2012 AACR.)

We report an unusual, rare case of primary epithelioid rhabdomyosarcoma of a lymph node in the parotid basin. A 72-year-old man with a history of squamous cell carcinoma of the forehead and cheek had a 5-cm mobile nontender mass of the parotid tail and right level II region. A positron emission tomography/computed tomography scan confirmed a hypermetabolic soft tissue mass in the right parotid gland. Histologic sections showed an intraparotid lymph node almost completely effaced by a centrally necrotic malignant epithelioid neoplasm consisting of uniform-appearing dyshesive cells exhibiting rhabdoid morphologic features with abundant eosinophilic fibrillary cytoplasm, eccentric nuclei, and prominent nucleoli. Bizarre cells were not seen. In immunohistochemical studies, neoplastic cells expressed desmin and myogenin. Electron microscopy showed a mixture of thick and thin filaments, primitive Z-band formation, and well-formed sarcomeres. Fluorescence in situ hybridization studies for FOXO1, PAX3, and/or PAX7 rearrangements were negative. An extensive clinical and radiologic workup showed no evidence of primary tumor elsewhere. Complete resection of the tumor was performed, and adjuvant chemotherapy was given; patient was disease free 12 months after surgery.