A rare case of tumor-to-tumor metastasis from thymic carcinoma to an ovarian mature teratoma.

Metastasis from one neoplasm to another is referred to as tumor-to-tumor metastasis (TTM). TTM is rarely observed. Here, we present a patient with TTM from a thymic carcinoma to an ovarian mature teratoma. A 25-year-old woman, diagnosed with unresectable thymic carcinoma, presented with a cyst with a solid tumor component in her right ovary. Laparoscopic cystectomy of the right ovary revealed that the solid tumor was a distant metastasis of the thymic carcinoma in an ovarian mature teratoma. The possibility of malignant transformation of the ovarian mature teratoma was ruled out, enabling accurate staging of the thymic carcinoma. This case emphasizes the need for clinicians to consider TTM and the importance of pathological confirmation of TTM when investigating potential distant metastases.