Definition: Relatively indolent tumors that arise in background of endometrial hyperplasia.
According to one definition, when endometrial glands show a confluent pattern occupying at least 2x2 mm focus, the diagnosis of adenocarcinoma can be made. Smaller foci are labeled "complex endometrial hyperplasia".
The diagnosis of endometrioid adenocarcinoma can also be made if there is extensive papillary pattern or infiltrative glands with desmoplastic response.
The glands are well-differentiated and show angulation or branching. Cytologic atypia is minimal.
The grading system currently used for endometrioid adenocarcinomas is the one proposed by International Federation of Gynecology and Obstetrics (FIGO).
If the tumor contains no more than 5% of solid, non-morular component, it is Grade 1. Grade 1 tumors make up approximately 50% of endometrial adenocarcinomas.
The glands are well-differentiated and show minimal cytologic atypia.
FIGO Grading system is based on the growth pattern of cancer - relative proportions of glandular vs solid components. It also takes into account cytologic atypia.
If a tumor with Grade 1 architectural pattern has severe cytologic atypia, it is classified as Grade 2. Such cases are rare and serous carcinoma should be ruled out.
Images
聽http://www.webpathology.com/image.asp?case=569&n=3
Microscopy
聽Back to back endometrial-type glands of varying differentiation/atypia with no intervening stroma 聽May occasionally show a villoglandular pattern 聽Stroma present is usually desmoplastic, may he foamy cells due to tumor necrosis (not specific for carcinoma, derived from stroma not histiocytes; fat positive, mucin negative) 聽Adjacent endometrium often exhibits EIN or atypical hyperplasia 聽Vascular invasion is associated with chronic inflammation around lymphatics 聽May he trophoblastic differentiation with hCG+ cells 聽Commonly has squamous metaplasia
FIGO grading
聽Well differentiated (FIGO grade 1)
Extensive, complex epithelial growth pattern with little intervening stroma Usually budding and branching of large glands causing papillary structures May be villoglandular on low power May he true papillae (DD: clear cell carcinoma, serous carcinoma), but without atypia Mild to moderate atypia is allowed or only focal; if atypia is more severe, FIGO grade is increased to moderate (FIGO grade 2) Some are myoinvasive Often has benign squamous differentiation (adenoacanthoma), focal mucinous, secretory or ciliated features Usually stage 1, with 95% relapse-free survival rate聽Moderately differentiated (FIGO grade 2)
6%-50% of non-squamous tumor is composed of sheet-like tumor cells without glandular features Tumor cells he moderate pleomorphism, prominent nucleoli聽Poorly differentiated (FIGO grade 3)
>50% of nonsquamous tumor is composed of sheet-like tumor cells without glandular features Tumor cells he high grade features Glands poorly formed when present May contain malignant squamous cells Angiolymphatic invasion commonMyometrial invasion
Myometrial invasion is an independent prognostic parameter of the endometrioid carcinomas which correlates with the risk of metastasis to pelvic and/or paraaortic lymph nodes.
Recognition of myometrial invasion is sometimes difficult. In fact, myoinvasion is overdiagnosed in routine practice in as many as 25% of the cases. Recently, it has been observed that tumor-associated macrophages stimulate angiogenesis and promote cancer dissemination.
There is a link between increased microvessel proliferation to stromal macrophage infiltrate and suggest that enhanced tumor angiogenesis, triggered by stromal macrophages, regulates the progression of endometrioid carcinomas.
The identical stroma microenvironment found in the primary and the corresponding metastatic tumor suggests that tumor stroma response is determined by the intrinsic biology of the tumor.
Predisposition
聽polycystic ovary disease
In patients with history of polycystic ovary disease, excessive estrogenic stimulation of the endometrium increases their risk of developing endometrial hyperplasia and carcinoma. Most endometrial carcinomas arising in this setting are well-differentiated and less likely to invade myometrium or metastasize.Differential diagnosis
聽Ciliary metaplasia 聽Papillary change 聽Progesterone treatment related changes 聽Shedding endometrium with papillary syncytial metaplasia 聽Villoglandular endometrioid carcinoma 聽Well differentiated tumors: atypical hyperplasia / EIN (Mod Pathol 2000;13:309) 聽Poorly differentiated tumors: serous carcinoma
References
聽Myometrial invasion and lymph node metastasis in endometrioid carcinomas: tumor-associated macrophages, microvessel density, and HIF1A he a crucial role. Espinosa I, Jos茅 Carnicer M, Catasus L, Canet B, D鈥檃ngelo E, Zannoni GF, Prat J. Am J Surg Pathol. 2010 Nov;34(11):1708-14. PMID: 20962622