Borderline Mucinous Tumors The mucinous tumor of low malignant potential is often difficult to diagnose. Although it is common to find a rather uniform pattern from section to section in the serous borderline tumor, this is not true in the mucinous tumors. Well-differentiated mucinous epithelium may be seen immediately adjacent to a poorly differentiated focus. It is important to take multiple sections from many areas in the mucinous tumor to identify the most malignant alteration (2).
Mucinous Carcinomas Bilateral tumors occur in 8% to 10% of cases. The mucinous lesions are confined to the ovary in 95% to 98% of cases (Fig. 37.5). Because most ovarian mucinous carcinomas contain intestinal-type cells, they cannot be distinguished from
Figure 37.4 High-grade serous adenocarcinoma. Papillae lined by sheets of cytologically malignant cells invade stroma, often with associated necrosis.
Figure 37.5 Mucinous adenocarcinoma of the ovary. Irregular glandular spaces are lined with a layer of tall columnar cells with abundant mucinous cytoplasm, resembling intestinal epithelium at the left. At the right, there is destructive invasion into the ovarian stroma.
metastatic carcinoma of the gastrointestinal tract on the basis of histology alone (2,6). Primary ovarian neoplasms rarely metastasize to the mucosa of the bowel, although they commonly involve the serosa, whereas gastrointestinal lesions frequently involve the ovary by direct extension or lymphatic spread (2).
Pseudomyxoma Peritonei Pseudomyxoma peritonei is a clinical term used to describe the finding of abundant mucoid or gelatinous material in the pelvis and abdominal cavity surrounded by fibrous tissue. It is most commonly secondary to a well-differentiated appendiceal mucinous neoplasm or other gastrointestinal primary; rarely, mucinous tumors arising in an ovarian mature teratoma are associated with pseudomyxoma peritonei.
Endometrioid lesions constitute 6% to 8% of epithelial tumors. Endometrioid neoplasia includes all the benign demonstrations of endometriosis. In 1925, Sampson suggested that certain cases of adenocarcinoma of the ovary probably arose in areas of endometriosis (19). The adenocarcinomas are similar to those seen in the uterine corpus. The malignant potential of endometriosis is very low, although a transition from benign to malignant epithelium may be demonstrated.
Borderline Endometrioid Tumors The endometrioid tumor of low malignant potential has a wide morphologic spectrum. Tumors may resemble an endometrial polyp or complex endometrial hyperplasia with glandular crowding. When there are back-to-back, architecturally complex glands with no intervening stroma, the tumor is classified as a well-differentiated endometrioid carcinoma. Some borderline endometrioid tumors have a prominent fibromatous component. In such cases, the term adenofibroma is used to describe them (2).
Endometrioid Carcinomas Endometrioid tumors are characterized by a markedly complex glandular pattern with all the potential variations of epithelia found in the uterus (Fig. 37.6).
Multifocal Disease The endometrioid tumors afford the greatest opportunity to evaluate multifocal disease. Endometrioid carcinoma of the ovary is associated in 15% to 20% of the
Figure 37.6 Endometrioid cancer. Round to tubular glands lined by stratified columnar cells with conﬂuent growth pattern.