Mucinous metaplasia with glandular structures of the labia minora
Mucinous metaplasia of the genital mucosa (MMG) is characterized by an alteration of the epithelium consisting of columnar cells with foamy mucinous cytoplasm.1 In previously reported cases, the squamous epithelial cells were simply replaced by columnar cells, and the overall structure with flattened surfaces was not significantly changed. In contrast, cases of MMG with glandular structures have not been reported. Here, we report such a case of MMG arising in the labium minor.
A 23‐year‐old woman noticed a painful erosion in the genital region 2 months before her initial visit to our hospital. She had been treated with vidarabine for suspected herpes simplex infection at a previous hospital, but the erosion had recurred on and off. The physical examination revealed a 3‐mm erythematous lesion on the left labium minor (Fig. 1a). Although scarring subsequent to herpes simplex infection was suspected, the lesion was resected for histopathological diagnosis. Histopathologically, the epithelium showed glandular structures with a micropapillary configuration, which was composed of a single layer of tall columnar epithelial cells (Fig. 1b). The epithelial cells had a foamy cytoplasm with basally oriented nuclei devoid of atypia (Fig. 1c–e). The columnar cells showed bulging of the apical cytoplasm, which indicates an apocrine‐type mucus secretion (Fig. 1e). Alcian blue and periodic acid–Schiff staining demonstrated abundant apical mucin in the epithelium (Fig. 1f,g). Immunohistochemically, the epithelial cells were positive for cytokeratin (CK)7, carcinoembryonic antigen, MUC5AC and MUC6 (Fig. 1h–j), but negative for CK20, gross cystic disease fluid protein 15, CDX‐2, MUC2, prostate‐specific antigen (PSA) and prostatic serum acid phosphatase (PSAP). Below the epithelium, a dense immune cell infiltration of lymphocytes, plasma cells and neutrophils was observed. From these findings, MMG was diagnosed.
Mucinous metaplasia of the genital mucosa is a rare disorder, with only a few cases having been reported.1 As the columnar epithelium is vulnerable to erosion, most cases of MMG showed recurrent erosive lesions in the same areas,1 and therefore, the clinical symptoms could resemble those of herpes simplex, as in our case. Although the exact pathogenesis remains unclear, various chronic inflammations have been speculated to cause its development.1
Mucinous metaplasia may show glandular structures in some tissues such as the endometrium. However, cases such as ours of MMG with glandular structures have not been reported. Morphologically, our case revealed an apocrine‐type mucus secretion, and such a finding may be seen in the endocervical glands and prostate glands.2, 3 The paraurethral Skene glands in females are considered homologous with the prostate gland, and occurrence of Skene gland‐like tissues in the female genital tract has also been reported.4 However, immunohistochemical studies demonstrated that MUC5AC and MUC6 were positive in our case, which was consistent with molecules expressed in the endocervical glands, whereas these molecules are not expressed in the prostate gland.5 In addition, PSA and PSAP, which are usually expressed in both the prostate gland and the Skene glands, were negative in our case.4 Collectively, these findings suggest that the MMG in our case showed clear differentiation of the endocervical glands, which might have caused the rare formation of the glandular structures.
Acknowledgment
We thank Flaminia Miyamasu (Medical English Communications Center, Faculty of Medicine, University of Tsukuba) for useful comments.
Conflict of Interest
None declared.
