Figure 35.2 Well-differentiated adenocarcinoma of endometrium. The glands and complex papillae are in direct contact with no intervening endometrial stroma, the so-called back-toback pattern. (Provided by Gordana Stevanovic, MD, and Jianyu Rao, MD, Department of Pathology, UCLA.)
Table 35.5 FIGO Definition for Grading of Endometrial Carcinoma
Histopathologic degree of differentiation:
Notes on pathologic grading:
Notable nuclear atypia, inappropriate for the architectural grade, raises a grade 1 (G1) or grade 2 (G2) tumor by one grade.
In serous adenocarcinoma, clear cell adenocarcinoma, and squamous cell carcinoma, nuclear grading takes precedence.
Adenocarcinomas with squamous differentiation are graded according to the nuclear grade of the glandular component.
FIGO Committee on Gynecologic Oncology. Revised FIGO staging for carcinoma of the vulva, cervix, and endometrium. Int J Gynecol Obst 2009;105:103–104.
Figure 35.3 Adenocarcinoma with squamous differentiation of endometrium. This lesion is also classified as adenoacanthoma. Squamous cells with eosinophilic cytoplasm and distinct cell borders form solid clusters in the lumina of neoplastic glands. (Provided by Gordana Stevanovic, MD, and Jianyu Rao, MD, Department of Pathology, UCLA.)
Avilloglandular configuration is present in about 2% of endometrioid carcinomas (94,95). In these tumors, the cells are arranged along fibrovascular stalks, giving a papillary appearance but maintaining the characteristics of endometrioid cells. The villoglandular variants of endometrioid carcinomas are always well-differentiated lesions that behave like the regular endometrioid carcinomas, and they should be distinguished from serous carcinomas. Secretory carcinoma is a rare variant of endometrioid carcinoma that accounts for about 1% of cases (96,97). It occurs mostly in women in their early postmenopausal years. The tumors are composed of well-differentiated glands with intracytoplasmic vacuoles similar to early secretory endometrium. These tumors behave as regular well-differentiated endometrioid carcinomas and have an excellent prognosis. Secretory carcinoma may be an endometrioid carcinoma that exhibits progestational changes, but a history of progestational therapy is rarely elicited. Secretory carcinoma must be differentiated from clear cell carcinoma because both tumors have predominately clear cells. These two tumors can be distinguished by their structure: secretory carcinomas have uniform glandular architecture, uniform cytology, and low nuclear grade, whereas clear cell carcinomas have more than one architectural pattern and a high nuclear grade.
adenocarcinoma. Features that favor a primary endometrial carcinoma are the merging of the tumor with areas of normal endometrial tissue, presence of foamy endometrial stromal cells, presence of squamous metaplasia, or presence of areas of typical endometrioid carcinoma. Positive perinuclear immunohistochemical staining with vimentin suggests an endometrial origin (100).
Serous Carcinoma About 3% to 4% of endometrial carcinomas resemble serous carcinoma of the ovary and fallopian tube (101–104). Most often, these tumors are composed of fibrovascular stalks lined by highly atypical cells with tufted stratification (Fig. 35.4). Psammoma bodies frequently are observed.