Expression and utility of IMP3 in the differential diagnosis of atypical glandular cells and adenocarcinoma in liquid-based cervical cytology

Abstract

Atypical glandular cell (AGC) interpretation in gynecological cytopathology presents many diagnostic challenges. We evaluated the expression of IMP3 in liquid-based cervical cytology and its utility in differentiating premalignant/malignant glandular lesions from benign/reactive processes. Additionally, we tried to determine whether IMP3 may be useful in differentiating among the types of uterine adenocarcinomas. Our cohort included 82 cases; 59 diagnosed with AGC and 23 with adenocarcinoma (Ac). IMP3 immunocytochemical stain was performed on ThinPrep slides and the results correlated with subsequent biopsy findings. IMP3 positivity was assessed by strong (2+ and 3+) granular cytoplasmic staining in at least one group of three epithelial cells. In the AGC group, IMP3 was positive in 14 (73.7%) of 19 cases that on histologic follow-up were confirmed Ac, and 39 (98.6%) of 40 non-glandular lesions/benign cases were negative. In the Ac group, IMP3 was expressed in 16 (69.6%) of 23 cases, of which 16 (72.2%) of 21 were uterine Ac. By combining the two groups, and excluding the 2 extrauterine carcinomas, IMP3 was positive in 30 (75%) of 40 uterine Ac, most of which (86.7%) were in situ/invasive endocervical Ac, and type II endometrial Ac (Papillary Serous and Clear Cell Carcinoma), and only 40% endometrioid Ac. In ThinPrep slides with AGC, IMP3 positivity predicts the presence of a significant endocervical or endometrial lesion on subsequent histology, and may also be a potential diagnostic tool useful in differentiating among the types of adenocarcinomas of the female lower genital tract.