What does atypical mucinous glandular proliferation mean in a endometrial biopsy?

The diagnostic line example is:

-Atypical mucinous glandular proliferation (see comment).

COMMENT:

Sections show crowded glands and papillae that lined by cytologically bland, mucinous epithelium. Atypical mucinous glandular proliferation should considered to be analogous to atypical endometrial hyperplasia (complex) and is the presumed precursor to endometrioid adenocarcinomas with prominent mucinous differentiation of the usual type. As always, this interpretation presumes a primary site in the endometrium, and clinical correlation is advised. A background endometrial polyp is present. The polyp displays focal mucinous changes, and may represent either the origin of the proliferation or is secondarily involved by the proliferation. The changes as seen in the current sample, are not diagnostic of a malignancy.

Only macronucleoli might be more concerning?

A study of 26 cases with interpretations from 4 pathologists and follow-up results showed carcinoma has a low interobserver variability but for AMGPs, it varies and very few cases showed carcinoma in the follow-up biopsy.

References:

1.Rawish KR, Desouki MM, Fadare O. Atypical mucinous glandular proliferations in endometrial samplings: follow-up and other clinicopathological findings in 41 cases. Hum Pathol. 2017 May;63:53-62. doi: 10.1016/j.humpath.2017.02.002. Epub 2017 Feb 21. PMID: 28232161.

2.Fadare O, Roma AA, Mhawech-Fauceglia P, Parkash V, Rabban JT. The diagnosis of mucinous lesions in endometrial samplings by gynaecological pathologists: an analysis of diagnostic reproducibility. Pathology. 2018 Apr;50(3):276-285. doi: 10.1016/j.pathol.2017.09.014. Epub 2018 Feb 8. PMID: 29428179.