Figure 1. Histopathological findings of endometrial mucinous metaplasia. A: Simple mucinous metaplasia exhibits small and simple tubular glands lined by a single layer of columnar, mucin-containing epithelium. Their bland nuclei are smaller in size than those of the non-mucinous endometrial glandular epithelium. B: Papillary mucinous metaplasia displays variable degrees of papillation. C: Cystically dilated glands possess prominent intraglandular papillary tufts and extracellular mucin. D: Some papillary cellular clusters show nuclear pseudostratification and overlapping, but obvious cytological atypia is absent. E: The mucinous epithelium of the papillary mucinous metaplasia shows round to ovoid nuclei, finely dispersed chromatin, and one or two conspicuous nucleoli. F: In certain cases, papillae show mixed inflammatory infiltrates, with neutrophils, eosinophils, and lymphocytes. Original magnification: A-B, ×100; C, ×40; D, ×200; E, ×400; F, ×100.