present­ in thecomas, it is much less than in lymphomas. Other malignant predominantly solid ovarian tumors, including ovarian cancer, metastases, and granulosa cell tumors, may resemble ovarian lymphoma, but these are more common than lymphomas. Bilaterally, high to intermediate SI on T2-weighted image and ascites favor the diagnosis of ovarian cancer. Metastases may also present as a lobulated unilateral or bilateral solid ovarian mass. They usually display strong contrast enhancement and central necrosis or cysts. History of cancer of the breast or the GI tract is pivotal for the differential diagnosis. Granulosa cell tumors tend to be unilateral and may cause estrogenic effects. Clinical history, presence of multiple lymph nodes, and splenomegaly support the diagnosis of secondary ovarian involvement in lymphoma.

7.4.3\ Ovarian Metastases

5–15% of malignant ovarian tumors constitute metastases to the ovaries. The GI tract (39%), breast (28%), and endometrium (20%) are the most common primary sites (De Waal et al. 2009; Lee et al. 2009; Brown et al. 2001; Young and Scully 2002b). Rare cancer sources include pancreatic and gallbladder cancer, melanoma, and lymphoma (Young and Scully 2002b). Ovarian metastases seem more common in premenopausal women because of higher vascularity of the ovaries in this age, and they may be associated with hormonal activity (Young and Scully 2002b). Although metastases may occur unilaterally (especially in endometrial cancer), bilateral involvement is a typical feature and found in 70–80% of ovarian metastases (Togashi 2003). Approximately 50% of ovarian metastases are Krukenberg tumors from stomach or colorectal cancers. Compared to other histologies, Krukenberg tumors have a fourfold risk to metastasize to the ovaries. In a multicenter study assessing 86 patients with primary ovarian and 24 patients with secondary cancers, only multilocularity favored the diagnosis of a primary ovarian cancer (Brown et al. 2001). Despite their large size, ovarian metastases are often asymptomatic. Out of 147 patients with predominantly gastrointestinal tract cancers, 36% of metastases

were detected synchronously (Li et al. 2012). In general, ovarian metastases are associated with a dismal prognosis. Colon cancer metastases have a significant better survival than stomach or breast cancer, where the majority of patients will die within the first year after detection (Li et al. 2012). Predisposing factors for metastases from breast cancer include premenopausal age, lobular carcinoma, and advanced stage. They typically develop 2–5 years after cancer diagnosis and are often also associated with peritoneal carcinomatosis (Bigorie et al. 2010).

Imaging Findings

Ovarian metastases may present as solid ovarian tumors with necrosis, as solid and cystic and rarely as multiseptate cystic masses (Koonings et al. 1989; Ha et al. 1995). Krukenberg tumors typically are bilateral oval or kidney-shaped tumors, which tend to preserve the contour of the ovary and have a nodular surface (Fig. 29). They are solid or predominantly solid with central necrosis or cysts and may attain a large size. On MRI, they display medium signal intensity on T1-weighted images and an inhomogeneous low to intermediate SI on T2-weighted images and DWI restriction (Ha et al. 1995; Kim et al. 1996). In CT and contrast-enhanced MRI, they tend to show strong enhancement of solid components or septations. Follicles may be preserved and displaced to the periphery. A transversing vessel may be present (Fig. 29). Ascites is commonly found and may be a sign of peritoneal seeding. Metastatic cancers different from Krukenberg tumors may have a variable appearance resembling other malignant ovarian lesions with cystic and mixed cystic and solid patterns (Brown et al. 2001; Young and Scully 2002b; Kim et al. 1996; Megibow et al. 1985). Colon cancer metastases commonly present as unilateral or bilateral, multiloculated, predominantly cystic tumors (Fig. 30) (Choi et al. 2006). Due to the high rate of synchronous ovarian metastases, careful assessment of the GI tract is warranted (Li et al. 2012). Further, in malignancy elsewhere, metastases to the ovaries should be suspected if the pattern of spread is atypical for ovarian cancer. In particular, the presence of pulmonary and hepatic ­metastases