MUC5AC and endometriosis: Histopathological findings of EC in the ovary include confluent (back-to-back) glands morphologic pattern, stromal invasion, cytoplasmic mucin, intracytoplasmic vacuoles, squamous metaplasia, and oncocytic and clear cell changes, and the presence of adenofibroma or endometriosis may be found in the background [16,17].