Lobular Endocervical Glandular Hyperplasia and Related Glandular Disorders: Current Status of Diagnosis with MR Imaging.

Lobular endocervical glandular hyperplasia (LEGH) is a rare benign lesion of the uterine cervix that produces gastric-type mucin. First identified in 1999, LEGH is often misdiagnosed as other glandular lesions, including adenocarcinoma, human papillomavirus (HPV)-independent, gastric-type (GAS), due to similar histopathological features. LEGH is now recognized as a precursor to GAS, a malignancy with poor prognosis. This review explores LEGH's pathological and immunohistochemical characteristics and related glandular lesions, focusing on diagnostic approaches using MRI. MRI has proven essential in distinguishing LEGH from other benign cervical cystic lesions and detecting precursor conditions, such as atypical LEGH, before progression to GAS. A hallmark MRI finding for LEGH is the "cosmos pattern," featuring centrally clustered microcysts surrounded by macrocysts, achieving 95.5% specificity when combined with T1-weighted imaging. Cytology and biopsy improve diagnostic accuracy when imaging results are inconclusive, though obtaining high-quality specimens can be challenging due to lesion location. This article reviews cytological findings, the presence of gastric-type mucin, and MRI features useful for differentiating LEGH from benign non-LEGH lesions, as well as for diagnosing precancerous and malignant conditions. Recent advances in research have led to the recognition that GAS is primarily a solid rather than a cystic lesion, contributing to improved diagnostic accuracy of MRI for GAS. However, some GAS cases and atypical LEGH can still exhibit a cosmos pattern on MRI, similar to LEGH, making differentiation challenging. Therefore, we also discuss a diagnostic strategy integrating MRI findings with cytology and presence or absence of gastric-type mucin.