Clinicopathological features of ectomesenchymoma

YE Danli; LAI Xuwen; YU Ling; YAN Guangning; LUO Jinxia; CUI Wenzhi; WANG Wei

doi:10.3969/j.issn.1007-8096.2025.09.002

Abstract：Objective To study the clinicopathological features,molecular features,and prognosis of ectomesenchymoma.Methods The clinical,pathological,and molecular data of two cases of ectomesenchymoma were analyzed and relevant literature was reviewed.Results Case 1 was a 1-month-old boy with a tongue mass detected at birth.Microscopically,three histological patterns were observed:loosely arranged short spindle cells in bundles,unshapely arranged immature primitive cells,and rhabdoid cells in glandular-like arrangements.Immunohistochemistry revealed that the three components expressed CD34 and S-100,CgA and Nestin,Desmin and Myogenin,respectively,which were diagnosed as neurofibroma,neuroblastoma,and rhabdomyosarcoma components.The patient underwent total tumor resection without adjuvant radiotherapy or chemotherapy.The tumor recurred in the 7th postoperative year,and the recurrent tumor was embryonal rhabdomyosarcoma.Case 2 was a 1-year-old girl with a 2-month history of a subcutaneous mass in the posterior neck.Microscopically,small to medium-sized immature cells were arranged in diffuse sheets or alveoli.Immunohistochemistry indicated that the two components expressed PGP9.5 and S-100,Desmin and Myogenin,respectively,which were neuroblastoma and alveolar rhabdomyosarcoma components.The patient underwent total tumor resection followed by radiotherapy,and the tumor recurred 1 year later.Conclusion Ectomesenchymoma is a rare biphasic differentiated soft tissue tumor composed of mesenchymal components(mainly rhabdomyosarcoma)and neuroectodermal components.A definite diagnosis requires the combination of histological morphology and immunohistochemical findings.Comprehensive treatment offers a relatively favorable prognosis.