Thymoma and thymic carcinoma associated with multilocular thymic cyst: a clinicopathologic analysis of 18 cases

BACKGROUND: Multilocular thymic cysts (MTCs) associated with thymomas or thymic carcinomas (TCs) are rare and may be misdiagnosed as other benign cystic lesions. METHODS: We retrospectively analysed 18 cases of thymomas or TCs associated with MTCs, which were retrieved from 309 consecutive patients with thymomas or TCs in the Chinese population, emphasizing clinicopathologic characteristics, immunophenotypes and the prognostic impact. RESULTS: A total of 14 tumours were described as cystic or solid-cystic masses, and the other 4 tumours were described as solid masses. Histologically, 2 atypical type A, 2 type AB, 1 type B1, 8 type B2, 1 type B3, 1 microscopic thymoma (type A), 2 squamous cell carcinomas (SCCs) and 1 lymphoepithelioma-like carcinoma (LELC) were classified. Prominent multilocular cystic areas with chronic inflammation were observed. The follow-up ranged from 2 to 79 months. Sixteen patients survived without any evidence of recurrence after complete resection. CONCLUSIONS: Our study suggests that thymomas or TCs associated with MTCs are rare in the Chinese population and have a better clinical behaviour than thymomas or TCs without MTCs. Our data also expand the histologic spectrum of thymomas or TCs accompanied by MTC. To our knowledge, this is the first report of atypical type A thymoma and LELC associated with MTCs.