Transvaginal ultrasonography may be a useful adjunct to endometrial biopsy for evaluating abnormal uterine bleeding and selecting patients for additional testing (84–87). Transvaginal ultrasonography, with or without endometrial ﬂuid instillation (sonohysterography), may be helpful in distinguishing between patients with minimal endometrial tissue whose bleeding is related to perimenopausal anovulation or postmenopausal atrophy and patients with significant amounts of endometrial tissue or polyps who are in need of further evaluation. The finding of an endometrial thickness greater than 4 mm, a polypoid endometrial mass, or a collection of ﬂuid
Table 35.4 Classification of Endometrial Carcinomas within the uterus requires further evaluation. Although most studies agree that an endometrial thickness of 5 mm or less in a postmenopausal woman is consistent with atrophy, more data are needed before ultrasonography findings can be considered to eliminate the need for endometrial biopsy in a patient with symptoms (88).
Pathology The histologic classification of carcinoma arising in the endometrium is shown in Table 35.4 (12,89).
The endometrioid type of adenocarcinoma accounts for about 80% of endometrial carcinomas. These tumors are composed of glands that resemble normal endometrial glands; they have columnar cells with basally oriented nuclei, little or no intracytoplasmic mucin, and smooth intraluminal surfaces (Fig. 35.2). As tumors become less differentiated, they contain more solid areas, less glandular formation, and more cytologic atypia. The well-differentiated lesions may be difficult to separate from atypical hyperplasia.
Criteria that indicate the presence of invasion and are used to diagnose carcinoma are desmoplastic stroma, back-to-back glands without intervening stoma, extensive papillary pattern, and squamous epithelial differentiation. These changes, with the exception of the infiltrating pattern with desmoplastic reaction, require an area of involvement equal to or exceeding one-half of a low-power microscopic field (LPF) (>1 LPF; 4.2 mm in diameter) (90,91).
The differentiation of a carcinoma, expressed as its grade, is determined by architectural growth pattern and nuclear features (Table 35.5). In the International Federation of Gynecology and Obstetrics (FIGO) grading system proposed in 1989, tumors are grouped into three grades: grade 1, 5% or less of the tumor shows a solid growth pattern; grade 2, 6% to 50% of the tumor shows a solid growth pattern; and grade 3, more than 50% of the tumor shows a solid growth pattern. The presence of notable nuclear atypia that is inappropriate for the architectural grade increases the tumor grade by one.
Adenocarcinomas with squamous differentiation are graded according to the nuclear grade of the glandular component. This FIGO system is applicable to all endometrioid carcinomas, including its variants, and to mucinous carcinomas. In serous and clear cell carcinomas, nuclear grading takes precedence; however, most investigators believe that these two carcinomas should always be considered high-grade lesions, making grading unnecessary.
About 15% to 25% of endometrioid carcinomas have areas of squamous differentiation (Fig. 35.3). In the past, tumors with benign-appearing squamous areas were called adenoacanthomas, and tumors with malignant-looking squamous elements were called adenosquamous carcinomas. It is recommended that the term endometrial carcinoma with squamous differentiation be used to replace these two designations because the degree of differentiation of the squamous component parallels that of the glandular component, and the behavior of the tumor is largely dependent on the grade of the glandular component (92,93).