Criteria for Squamous Differentiation of the International Society of Gynecologic Pathologists -When a solid focus of tumor in an endometrioid-type carcinoma shows one or more of the following:
(1) keratinization demonstration by a standard staining technique
(2) intercellular bridges
(3) 3 or 4 of the following
(3a) sheet-like growth without gland formation or pallisading
(3b) sharp cell margins
(3c) eosinophilic and thick or glassy cytoplasm
(3d) cells with significantly more abundant cytoplasm than nonsquamous tumor cells
Criteria for malignancy in squamous component - one or more of the following:
(1) standard cytologic criteria for malignancy
(2) mitoses in the indisputably squamous component
(3) destructive stromal infiltration by the stromal elements
Classification of tumor based on features of squamous component:
(1) If the squamous component is histologically malignant, then it is an adenosquamous carcinoma
(2) If the squamous component is not histologically malignant, then it is an adenocarcinoma with squamous metaplasia, or adenoacanthoma.
(3) If no squamous component is present, then it is an adenocarcinoma.
