Warthin tumor concomitant with mantle cell lymphoma: a case report and review of literature.

Rationale: Warthin tumor (WT) is the second most common benign tumor in salivary gland. It has a slow growth rate and most frequently occurs in the parotid gland. Most patients present with an incidental finding of a painless mass inferior/anterior to the ear. Besides the epithelial component of the tumor, WT is characteristically associated with lymphoid stroma that is considered benign. While there have been a few reports of malignant transformation of the lymphoid components in WT, cases of WT concomitant with mantle cell lymphoma (MCL) are extremely rare. To the best of our knowledge, two cases have been described in the English literature. Herein, we report a case of WT concomitant with MCL in a 70-year-old female patient, and emphasize the importance of careful examination of lymphoid stroma in WT so that concurrent lymphoma is not missed.

Patient concerns: A 70-year-old Chinese woman with a 40-year history of cigarette smoking presented with a one year history of a right submaxillary mass with recent enlargement.

Diagnosis: Cervical ultrasound (US) and computed tomography (CT) scans of the neck revealed a well-circumscribed mass in the right parotid with a maximum diameter of 3.1 cm. Surgical resection of the mass was performed. Histopathological examination revealed a characteristic double-layer of neoplastic epithelium with prominent lymphoid stroma, suggesting WT. In addition, morphology and immunohistochemistry studies confirmed the coexistence of MCL. Thereafter, the final diagnosis of this case was WT concomitant with MCL.

Interventions: The patient was staged as stage I after clinical assessment. Due to the slow growth of parotid lesions, close observation was decided with periodic clinical and radiological monitoring.

Outcomes: Currently, the patient demonstrates a stable disease by clinical evaluation.

Lessons: To the best of our knowledge, reported cases of WT concomitant with MCL are very rare. This case highlights the importance of a comprehensive assessment of the lymphoid stroma of WT to avoid missed diagnosis of a lymphoma component in a collision tumor.