Diagnostic significance of endocervical glandular cells with "golden-yellow" mucin on pap smear

Endocervical glandular cells rarely show "golden-yellow" mucin staining using the Papanicolaou technique, whereas the cells of adenoma malignum (minimal deviation adenocarcinoma) do. To further evaluate the significance of this finding, we reviewed the Pap smears of six cases in which atypical glandular cells containing golden-yellow mucin was identified. Microscopic examination of the hysterectomy specimens confirmed one case of adenoma malignum, whereas the other five cases were diagnosed as endocervical glandular hyperplasia with pyloric gland metaplasia. Glandular cells observed in all six cases were filled with golden-yellow mucin. In the case of adenoma malignum the nuclei were somewhat more enlarged and the chromatin texture was coarsely granular, although a distinction between adenoma malignum and the five benign lesions was difficult. Special staining performed on tissue sections in all cases demonstrated that the intracytoplasmic mucin of the glandular cells in portion of both pyloric gland metaplasia and adenoma malignum was predominantly PAS-positive and showed immunoreactivity for M-GGMC-1 (HIK1083), which reacts with pyloric gland mucin of the stomach. A review of 1,165 consecutive Pap smears failed to identify cells with golden-yellow mucin. These observations indicate that golden-yellow mucin on Papanicolaou smear seems to represent a gastric phenotype of endocervical glandular cells, which is a unique characteristic shared by adenoma malignum and pyloric gland metaplasia. This finding should therefore be regarded as a warning sign, raising the possibility of adenoma malignum and requiring prompt histopathologic assessment, although not of itself diagnostic of malignancy.