Novel classification of ovarian metastases originating from colorectal cancer by radiological imaging and macroscopic appearance.

ABSTRACT

BACKGROUND: Diagnosis of secondary ovarian tumors originating from colorectal cancer has previously been based upon history of malignancy and radiological findings of bilateral masses with a "stained glass appearance." The purpose of this study was to perform a detailed investigation of the radiological and macroscopic features of ovarian metastases originating from colorectal cancer, which remain to be fully characterized. METHODS: Study participants were 48 consecutive patients with ovarian metastases from colorectal cancer who underwent resection of ovarian tumors at the National Cancer Center Hospital between August 1998 and January 2019. Ovarian tumors were classified into subgroups using computed tomography (CT), magnetic resonance imaging (MRI), and macroscopic appearance. RESULTS: CT/MRI findings and macroscopic appearance were classified into the following four types type 1 (oval, homogeneous-solid) (n = 5); type 2 (heterogeneous-solid, small in size with multinodular surface) (n = 3); type 3 (solid-cystic, predominantly solid) (n = 18); and type 4 (cystic-solid, multilocular with solid components) (n = 22). Type 1 mimics Krukenberg tumors, type 2 mimics ovarian metastases from breast cancer, type 3 mimics primary ovarian endometrioid cancer, and type 4 mimics primary ovarian mucinous cancer, with a "stained glass appearance". Twenty-eight (58%) patients had bilateral metastases. Eleven patients (23%) underwent hysterectomy and/or pelvic lymph node dissection in addition to ovarian resection. CONCLUSION: We introduced a novel classification system for ovarian metastases originating from colorectal cancer, which may be beneficial for assessing ovarian metastases from colorectal cancer and avoiding unnecessary surgery due to misdiagnosis of primary ovarian tumors.