Intrathyroidal thymic carcinoma (ITC) is a rare thyroid tumor that resembles thymic carcinoma, for which there are no recommendations on diagnostic and therapeutic approaches. We performed a pooled analysis of published ITC cases to describe the natural history of this disease and identify prognostic factors. We performed a systematic review of histopathological-confirmed ITC cases published in the literature in English. The following keywords were used: 'intrathyroidal thymic carcinoma', 'carcinoma showing thymus-like differentiation', 'CASTLE tumor', 'thyroid carcinoma showing thymus like differentiation'. Fifty eligible publications were identified, providing data from 132 patients, plus a case diagnosed at our institution. Median disease-free survival (DFS) of this patient series was 144 months (range 91–197), while median overall survival (OS) was not reached. Upfront surgery was performed in 97% of patients and 24% of them experienced disease recurrence after a median of 19 months (range 13–25). Complaining of major symptoms, as a sign of more advanced local stage, was the only prognostic factor significantly associated with a higher risk of death at multivariate analysis (HR 4.903, 95% CI: 1.092–22.008, P = 0.038). Postoperative radiation therapy was not associated with prognosis, while not enough data were available to assess the efficacy of chemotherapy. ITC is a rather indolent disease and ITC patients have a relatively good prognosis. Surgery is the mainstay of therapy. Survival outcome of patients depends on tumor burden and complete surgical resection. Postoperative radiation effect seems to be negligible. Data on the efficacy of chemotherapy in advanced patients are lacking.