[Clinicopathological and molecular genetic characteristics of embryonal rhabdomyosarcoma in the middle ear: an analysis of 11 cases].

Objective: To investigate clinicopathologic characteristics and molecular genetic profiles of embryonal rhabdomyosarcoma (ERMS) of the middle ear. Methods: A total of 11 cases of primary middle ear ERMS diagnosed and treated at the Fudan University Affiliated Eye and ENT Hospital between January 2016 and June 2024 were collected. Their clinicopathologic features, immunophenotypes, and molecular genetic alterations were analyzed. Relevant literature was reviewed. Results: There were 8 male and 3 female children. The mean age was 6 years, median age, 6 (5, 7) years, with a range of 1 to 11 years. Clinical manifestations included otorrhea, ear pain, ear fullness, tinnitus, and hearing loss, with some patients also presenting with facial paralysis, hoarseness, and choking on drinking. Otoscopic examination revealed granulomatous neoplasms in the external auditory canal. Imaging studies showed irregular soft-tissue masses in the middle ear region, accompanied by bony destruction and invasion of adjacent structures. Histologically, 10 of the tumors were composed of primitive small round cells, stellate cells, and short spindle-shaped cells, with an alternating loose and dense distribution pattern, and varying degrees of rhabdomyoblastic differentiation in some areas. One tumor exhibited the classic botryoid subtype morphology. Immunohistochemistry supported the diagnosis of rhabdomyosarcoma, and the Ki-67 proliferation index ranged from 40% to 80%. Next-generation sequencing (DNA-seq) was performed on 9 cases, revealing copy number variations of chromosome 7 in 4 cases, PDE4DIP mutations in 5 cases, and C19orf69::TPM3 gene fusions in 6 cases. HPV PCR testing showed HPV11 positivity in 2 cases. All 11 patients underwent surgical treatment, with 4 patients receiving adjuvant chemoradiotherapy. Follow-up until February 2025 revealed 8 deaths, among which 4 cases harbored both C19orf69::TPM3 fusions and PDE4DIP mutations and one had C19orf69::TPM3 fusions alone. Conclusions: ERMS of the middle ear is a rare type of malignant tumor with a relatively poor prognosis. Our study indicates that the concurrence of PDE4DIP mutation and C19orf69::TPM3 gene fusion may indicate poor prognosis in middle ear EMRS, providing a potential target for subsequent individualized treatment.