Progressive MRI changes in lobular endocervical glandular hyperplasia suggesting malignant transformation: report of two cases with histopathologic correlation.

Lobular endocervical glandular hyperplasia (LEGH), a benign multicystic lesion that typically occurs in the upper uterine cervix, is regarded as a potential precursor lesion of gastric-type adenocarcinoma (GAS), including its well-differentiated form, minimal deviation adenocarcinoma (MDA). On MRI, LEGH characteristically shows the "cosmos sign," consisting of clustered small central cysts surrounded by larger peripheral cysts on T2-weighted images. However, MDA arising from LEGH can yield similar findings. Differentiation by MRI is therefore often challenging. This report describes two premenopausal women with MDA associated with previously diagnosed LEGH who underwent serial MRI follow-up. In both cases, T2-weighted images showing the cosmos sign revealed progressive enlargement of a central hypointense area with concomitant shrinkage of the surrounding cysts. Neither showed any readily apparent increase in overall lesion size. During follow-up after the initial diagnosis/conization, cytology remained negative for intraepithelial lesion or malignancy. In case 1, hysterectomy revealed MDA associated with previously diagnosed LEGH. The central hypointense area corresponded to tumor-associated reactive fibrotic stroma containing infiltrative glands with nuclear enlargement and mitoses. In case 2, hysterectomy showed deeply extending, morphologically diverse glands associated with reactive fibrotic stroma suspicious for invasion. The central hypointense area again corresponded to predominantly fibrotic stroma. These cases suggest that progressive expansion of a central low-signal-intensity area on T2-weighted images, accompanied by shrinkage of peripheral cysts, might constitute an early imaging sign of transition from LEGH to MDA, even without overall LEGH enlargement or worsening cytology. Such expansion should therefore be assessed carefully on follow-up MRI.