298 Synchronous Ipsilateral Warthin’s Tumor and Basal Cell Adenocarcinoma of Parotid Gland: An Ultrarare Case Report

Introduction/Objective Synchronous occurrence of benign and malignant tumors within the same salivary gland is a rare clinical entity, posing diagnostic and therapeutic challenges. Warthin’s tumor is the second most common benign neoplasm of the parotid gland, while basal cell adenocarcinoma (BCAC) is a rare low-grade malignant salivary gland tumor. The simultaneous presence of these two distinct histopathological entities in the ipsilateral parotid gland is exceptionally uncommon and has been infrequently reported in the literature. Methods/Case Report A 66-year-old male with a history of bilateral parotidectomies for Warthin’s tumors 20 years ago presented with a progressively enlarging left parotid mass. MRI and CT imaging confirmed a new lesion, and fine-needle aspiration revealed a neoplasm of uncertain malignant potential. The patient underwent a left revision deep lobe parotidectomy. Histopathological analysis revealed a synchronous Warthin’s tumor (2.5 cm) and a basaloid cell proliferation consistent with basal cell adenocarcinoma (BCAC), characterized by canalicular architecture, mitotic figures, apoptotic debris, and focal perineural invasion. Immunohistochemistry and FISH for MYB gene rearrangement confirmed the diagnosis of BCAC. Core biopsies of the residual deep lobe confirmed residual BCAC. The patient subsequently underwent a left radical total parotidectomy with skull base resection. Final pathology demonstrated a 6 cm BCAC with extensive necrosis and perineural invasion. Surgical margins were positive across all planes, including the skull base, although regional lymph nodes were negative (pT4bN0M0). Given the high-risk features—positive margins and perineural invasion—postoperative adjuvant radiotherapy was initiated. This case highlights a rare synchronous presentation of Warthin’s tumor and BCAC within the same gland, emphasizing the need for comprehensive evaluation and aggressive management in complex salivary gland tumors. Results NA Conclusion To the best of our knowledge, this is the earliest documentation of ipsilateral synchronous Warthin’s tumor and basal cell adenocarcinoma arising within the parotid gland. The unique presentation of this case underscores the complexity of salivary gland tumor diagnosis. Accurate diagnosis through imaging, histopathology, and molecular testing, combined with aggressive surgical management and adjuvant therapy, is critical for optimal outcomes in advanced-stage salivary gland malignancies.