Early local recurrence of well-differentiated liposarcoma of the hypopharynx in a young adult: a case report and literature review.

Well-differentiated liposarcoma (WDLPS), also termed atypical lipomatous tumor, is a low-grade malignant adipocytic neoplasm characterized by indolent growth, limited metastatic potential, and a propensity for local recurrence. Primary WDLPS arising in the hypopharyngeal region is exceptionally rare, particularly in young adults, and may clinically mimic benign submucosal lesions. We report the case of a 24-year-old man who presented with a one-month history of persistent foreign body sensation in the throat. Flexible laryngoscopy revealed a smooth submucosal mass arising from the left hypopharyngeal region, and contrast-enhanced magnetic resonance imaging demonstrated a well-circumscribed enhancing lesion without cervical lymphadenopathy. The mass was excised transorally under general anesthesia. Histopathological examination showed mature adipocytic proliferation with atypical stromal cells, and immunohistochemistry demonstrated positivity for MDM2, CDK4, CD34, and p16. Fluorescence in situ hybridization confirmed MDM2 gene amplification, establishing the diagnosis of WDLPS. Although the early postoperative course was uneventful and initial follow-up showed satisfactory mucosal healing, serial laryngoscopic examinations at 2, 2.5, and 4 months after surgery revealed early local recurrence at the surgical site. This case highlights that hypopharyngeal WDLPS can occur in young adults and may recur early even after apparently complete transoral excision. Accurate diagnosis requires integration of histopathology, MDM2/CDK4 immunohistochemistry, and molecular confirmation of MDM2 amplification. Close endoscopic and radiological surveillance is essential for early detection of local recurrence.