Adenoid cystic carcinoma of the thymus: a case report and literature review.

Primary adenoid cystic carcinoma (ACC) of the thymus is extremely rare. Although thymic ACC is generally slow growing, complete surgical resection is essential due to its tendency for local invasion. Here, we report a case of primary thymic ACC successfully treated by complete resection using a single-port subxiphoid thoracoscopic approach. A 63-year-old asymptomatic male patient was referred after an anterior mediastinal mass was incidentally detected during a routine health screening. Imaging revealed a small, well-circumscribed tumor without evidence of invasion. At 2.2 cm, the lesion was among the smallest thymic ACCs reported to date. Thymoma was suspected and single-port subxiphoid thoracoscopic thymectomy was performed. The patient's postoperative course was uneventful. The histopathological and immunohistochemical findings were consistent with ACC, and no other primary lesion was identified. Complete resection was achieved with minimally invasive thymectomy. This case illustrates that thymic ACC may rarely present as a small, early-stage tumor indistinguishable from thymoma, and it highlights the importance of complete resection with negative margins and long-term surveillance given the potential for delayed recurrence.