ERBB2/ERBB3‑mutated S100/SOX10‑positive high‑grade uterine sarcoma-a case report on a rare entity

ERBB2/ERBB3‑mutated S100/SOX10‑positive uterine sarcoma is a recently described entity with distinct morphological, immunophenotypic, and molecular features, representing a subset of high-grade uterine sarcomas. This tumor is characterized by ERBB2/ERBB3 mutations or ERBB2 amplification, which leads to the overexpression or constitutive activation of HER2. The presence of HER2 amplification represents a potential target for the treatment with HER2 inhibitors. Here we present a case of high-grade uterine cervix sarcoma with ERBB2 amplification and S100/SOX10 expression in a 58-year-old patient. The tumor measured 50 mm at its largest dimension and recurred two years after surgery. Histologically, the tumor was composed of round and spindle cell, showing diffuse nuclear expression of SOX10 and both nuclear and cytoplasm expression of S100. It also demonstrated ERBB2 amplification, as well as mutations in ATRX and BACH1. Accurate recognition of such tumors is crucial due to their propensity for aggressive behavior and the availability of potential targeted therapeutic options.