The challenge of diagnosing a malignancy metastatic to the ovary: clinicopathological characteristics vary and morphology can be different from that of the corresponding primary tumor

An accurate diagnosis of metastases to the ovary is essential for adequate patient management. The aim of this retrospective study was to characterize clinicopathological features of metastatic malignancies that presented as an ovarian mass and compare them with their corresponding primary tumors. We reviewed clinical files and histological material of 120 patients with metastases to the ovary, diagnosed in our center between 2000 and 2014. Metastases were diagnosed before (18 %), synchronously (33 %), or after (49 %) the primary tumor was identified; 25 % were single, 40 % were unilateral; 47 % were ≥13 cm. Most originated from the gastrointestinal tract (73 %), followed by breast (13 %), and female reproductive organs (10 %). Gross features varied with primary tumor site. Metastases from gastrointestinal malignancies were significantly larger and frequently showed necrosis. Metastases to the appendix were cystic (94 %), and almost all metastases to the stomach (96 %) and breast (87 %) were solid. The predominant histological pattern was discordant in 44 % cases, mostly due to cystic changes in ovarian metastases which were observed across several histological types. Other metastases showed a predominant histological pattern which was present only focally in the primary tumor. Metastases showed significantly more edema, necrosis, and hemorrhage, but less lymphovascular invasion and inflammatory infiltrate than the corresponding primary tumors. Metastases to the ovary present highly variable clinicopathological features which frequently differ from those of the corresponding primary tumor. A metastasis should always be considered in the differential diagnosis of an ovarian mass. All clinical, imaging, macroscopic, and histological aspects must be taken into account to establish a correct diagnosis which is essential for adequate treatment.