LAUSR

AIMS Distinction between well-differentiated endometrial carcinoma (EMCA) with microglandular/mucinous features and benign endocervical microglandular hyperplasia (MGH) can be a diagnostic challenge, especially when tissue is limited. The immunostains used to distinguish endocervical and endometrial carcinoma are less useful when the differential diagnosis is MGH. Here, we investigate the utility of p63 and PTEN to aid accurate classification. METHODS AND RESULTS Cases obtained from our pathology archives included 25 EMCA with mucinous/microglandular features, 26 MGH, and 9 atypical microglandular proliferations. Cases were assessed for glandular architecture, presence of mucinous and/or eosinophilic luminal secretions, subnuclear vacuoles, foamy histiocytes, inflammation, squamous metaplasia, cytologic atypia and mitotic activity. The presence and pattern of immunohistochemical staining for p63 and PTEN was recorded. Microglandular proliferations with cytologic atypia, mitotic activity, foamy histiocytes and complex glandular architecture were more commonly seen in EMCA, while small glands, bland nuclei, and subnuclear vacuoles were enriched in MGH. All MGH cases displayed p63-positive subcolumnar reserve cells and retained PTEN expression. Four EMCA cases showed non-specific focal p63 staining either at the surface of the tumor or in areas of squamous differentiation. p63 and PTEN immunostains accurately predicted the final diagnosis for 3 atypical microglandular proliferation cases with follow-up. CONCLUSIONS While there are morphologic characteristics that differentiate EMCA and MGH, there is frequent overlap between these entities. Nonetheless, the pattern and extent of p63 and PTEN can aid accurate classification. Consistent p63-positive subcolumnar reserve cells were seen only in MGH.