Atypical Lipomatous Tumor/Well-Differentiated Liposarcoma of the Salivary Gland and Its Diagnostic Challenges: A Case Report and Literature Review

Atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDLPS) is a low-grade adipocytic neoplasm composed of mature adipocytes with at least focal nuclear atypia in adipocytes and stromal cells. The terms “atypical lipomatous tumor” and “well-differentiated liposarcoma” are site-dependent terms for the same morphological and genetic entity. Amplification of MDM2 and/or CDK4 is almost always present and is a defining molecular feature. It usually arises in deep soft tissue. Primary head-and-neck involvement is rare, and salivary gland tumors are exceptionally uncommon. Only a few salivary gland tumors have been reported and accurate diagnosis may be challenging because they can mimic benign lipomatous lesions. ALT lacks metastatic potential unless dedifferentiation occurs, but it carries a significant risk of local recurrence. Careful histology plus MDM2 gene testing improves diagnostic accuracy. We report a 59-year-old man presenting with a recurrent parotid mass 7 years after a lipoma excision at an outside facility. Imaging showed involvement of both superficial and deep lobes of the left parotid gland. The facial nerve was preserved during surgery, and the postoperative course was uneventful. Histologic examination of the reexcision specimen showed mature adipose tissue with adipocyte size variation and focal atypia within fibrous septa; fluorescence in situ hybridization confirmed MDM2 amplification, establishing ALT. This case report aims to highlight the diagnostic challenges of ALT in uncommon locations such as the parotid gland and to evaluate strategies for accurate recognition and effective management, with emphasis on avoiding misdiagnosis and ensuring complete surgical excision.