TTM is defined as metastasis in distinct tumors of the same body, and 15 cases of TTM in ovarian tumors have been reported to date [5]. OMTs causes various cancers via malignant transformation; therefore, the coexistence of OMT and cancers requires the differentiation between primary and metastatic cancers.

Ten cases of primary malignant lymphoma derived from OMT have been reported [7, 8]. TTM of malignant lymphoma to OMT is the only existing case of plasmablastic lymphoma [9]. TTM to OMT is summarized in Table 1 [3, 5, 6, 9] and shows that the present case is the first recorded case of nodal follicular lymphoma metastasizing and extending to the OMT. Historically, the most common method for diagnosing TTM to OMT was immunohistochemical analysis (4/5 cases), followed by virological examination and FISH, which were performed in two cases each. This is the first molecular analysis report that combines G-banding and FISH. These results recommend molecular diagnostic approaches for TTM and OMT when morphological and immunohistochemical findings alone are insufficient for diagnoses.

Ozsan et al. divided 16 follicular lymphomas initially diagnosed in the ovary into two groups based on clinical, morphological, immunophenotypic, and genetic features [10]. Ozsan et al. reported that ovarian extension of nodal follicular lymphoma was characterized as low histologic grade, BCL2 protein positivity, and presence of t(14;18)(q32;q21), while true primary ovarian follicular lymphoma was characterized as higher histologic grade, CD10 and BCL2 negativity, and absence of t(14;18)(q32;q21) [10]. We diagnosed the present case with TTM from nodal follicular lymphoma to OMT based on the distribution of lymph node lesion (pelvic to axillary), genetic analysis of t(14;18)(q32;q21), immunohistochemical expression of BCL2 and CD10, and histologic grades (grade 1). However, this study included only one case of OMT [10]. It is unclear whether OMT-derived follicular lymphoma has the same biology as that of a conventional follicular lymphoma. Tamura et al. reported that SCCs derived from OMTs share genetic characteristics with pulmonary SCCs rather than cutaneous SCCs, which is the most common component of OMTs [11]. It is expected that more cases will be accumulated in the future.