Detection of pagetoid urothelial intraepithelial neoplasia extending to the vagina by cervical screening cytology: a case report with renewed immunochemical summary

Extensive urothelial carcinoma (UC) involves various organs along the urinary tract and often has a long history of relapse [1]. Pagetoid spread of UC to the lower genital tract is rare and difficult to diagnose, especially in remote recurrences without apparent macroscopic lesions. We describe a case of metachronous UC with pagetoid spread to the vagina, which was diagnosed by cervical cytology and vaginal biopsy, and herein summarize the clinicopathologic differences among Paget-like neoplasms of the lower genital tract with recent immunocytochemical/immunohistochemical markers.

Female genital organs can be synchronously or metachronously involved in bladder cancer, with vaginal involvement predominating. Recently, Salem et al. reported on 360 women who underwent radical cystectomy for bladder cancer, of which 13 (3.6%) had vaginal involvement and 1 had uterine spread [2]. Similarly, Djaladat et al. found vaginal involvement in at least 10 (3.7%) of 267 women who underwent cystectomy with reproductive organ removal [3]. Although the morphologic pattern of vaginal involvement is unclear in those studies, pagetoid spread of UC is considered much rarer; Gregori et al. reported that only 2 of 98 cases of vulvar Paget disease were related to bladder UC [4]. In the present case, biopsy revealed both the vulvar and vaginal involvement by UC whereas there was no evidence of uterine involvement in the specimen of cervical conization.

Pagetoid spread of carcinoma is characterized by proliferation of individual or clustered tumor cells in the lower part of the juxtaposed squamous epithelium. Vulvar pagetoid neoplasm of urothelial origin is the secondary, noncutaneous type of extramammary Paget disease, which was termed pagetoid urothelial intraepithelial neoplasia by Wilkinson and Brown [5]. Pagetoid urothelial intraepithelial neoplasia can involve the vagina, uterine cervix, and rarely the endometrium [6]. Although primary and secondary types of Paget disease have overlapping clinical presentations, histologic distinction is usually straightforward; the former is characterized by Paget cells with abundant pale cytoplasm with rare mitoses, while the latter usually displays severe disarrangement of neoplastic cells with mitotic activity often showing pleomorphism/anaplasia [6] (Table 1). However, to avoid diagnostic challenges, diagnosis of pagetoid urothelial intraepithelial neoplasia often requires detection of specific markers of urothelial differentiation. UC typically shows positivity for high-molecular-weight CK and p63 with coexpression of CK7 and CK20 in 50 to 80% of cases [7]. Both uroplakin III and thrombomodulin are highly specific to UC [7], and a newer marker, uroplakin II (clone BC21), demonstrates improved sensitivity (around 80%) and positive intensity compared with uroplakin III [8]. While a panel of these antibodies is generally sufficient for differential diagnosis, the history of prior UC provides the most important diagnostic clue for pagetoid urothelial intraepithelial neoplasia.

LBC has recently been widely applied to various samples with subsequent immunocytochemistry as a useful diagnostic tool. In the present case, the absence of p16 labeling on CINtec® PLUS with positivity for GATA3 led the pathologist to suspect pagetoid urothelial intraepithelial neoplasia, which was confirmed upon obtaining the clinical history. However, careful attention is needed when using these two relatively new markers because UC must be discriminated from mimics (Table 1). Piaton et al. investigated p16/Ki-67 dual labeling in urinary cytology and found p16 positivity in 93 (93.9%) of 99 high-grade urothelial cells, among which coexpression of p16/Ki-67 in the same cells was noted in 80 (79.2%) of 101 high-grade tumors [9]. It is noted that the weak p16 staining is usually considered negative. GATA3 is not useful for distinguishing pagetoid urothelial intraepithelial neoplasia from primary extramammary Paget disease; Zhao et al. recently reported that almost all 72 cases of primary vulvar Paget disease were positive for GATA3 [10]. However, GATA3 is helpful to exclude either secondary Paget disease of colorectal origin or high-risk HPV-associated neoplasm [11, 12]. Therefore, to ensure the diagnosis of pagetoid urothelial intraepithelial neoplasia, adenocarcinoma must be excluded using reliable markers such as CEA and GCDFP15 in addition to specific high-risk HPV detection in cervical cytology.

In summary, we have presented an unusual case of pagetoid urothelial intraepithelial neoplasia with extension to the vagina in a woman who underwent left nephroureterectomy and subsequent radical cystectomy for metachronous UC, highlighting LBC with immunocytochemical pitfalls. Pagetoid urothelial intraepithelial neoplasia of the lower genital tract is difficult to diagnose without symptomatic lesions typical to Paget disease, such as pruritic eczema in the vulvar vestibule and/or periurethral region. Pathologists should nevertheless consider remote recurrence of UC in cervical cytology with special attention to absence of p16 labeling despite high-grade morphology as a pointer to the diagnosis of urothelial cancer. Using further biopsy and immunohistochemical confirmation of UC relapse, investigation to rule out invasive malignancies and careful follow-up throughout the patient’s lifetime is recommended.