Aims SOX17 expression has not been studied in glandular lesions of the uterine cervix like adenocarcinoma in situ (AIS) and invasive adenocarcinomas (AdC), whereas SOX17 promoter CpG island methylation has been reported. Therefore, the aim of this study was to relate the topographical distribution of SOX17 expression and SOX17 methylation status to each other, and to SOX2 expression, human papillomavirus (HPV) type, and physical status of the virus. Methods and results Immunohistochemistry was used in 45 cases to assess expression of SOX17 and SOX2. SOX17 promoter methylation was determined in 25 cases by means of bisulphite conversion and methylation‐specific polymerase chain reaction. SOX17 and SOX2 showed a mutually exclusive expression pattern in normal epithelium, with a sharp delineation in the squamocolumnar junction. SOX17 was found in endocervical columnar and reserve cells, whereas SOX2 was exclusively found in squamous epithelium. In both glandular lesions and cases with coexisting glandular and squamous intraepithelial components, a complex combination of SOX17 and SOX2 expression patterns was seen and mutually exclusive expression was lost. Frequently, gain of expression of SOX2 was found and expression of SOX17 was lost. Methylation of the CpG island in the SOX17 promoter was shown to be strongly associated with loss of expression of SOX17 (P = 0.0016). Conclusions In this study, we show for the first time a direct correlation between the topographical distribution of SOX17 expression and the methylation status of its gene promoter. This explains the heterogeneity of SOX17 expression in the glandular lesions of the cervix. No correlation was found between HPV type and physical status of the virus on the one hand and methylation status on the other.

Aims The dynamics and topographical distribution of SOX17 and SOX2 expression was studied in the transformation zone (TZ) of the uterine cervix. This TZ is a dynamic area where switches from glandular into squamous epithelium can be recognized, new squamocolumnar junctions are formed, and premalignant lesions originate. SOX17 and SOX2 show mutually exclusive expression patterns in the normal uterine cervix, with SOX2 being exclusively found in squamous epithelium, while SOX17 is detected in endocervical columnar cells and reserve cells. Methods and Results Normal cervices and squamous intraepithelial lesions (SIL) were studied with immunohistochemistry, methylation of SOX17, human papilloma virus (HPV) genotyping, and in situ hybridization. In the TZ squamous metaplasia originating from these reserve cells can still show SOX17 expression, while also remnants of SOX17‐positive immature metaplasia can be recognized in the normal squamous epithelium. SOX17 expression is gradually lost during maturation, resulting in the exclusive expression of SOX2 in the majority of (SIL). This loss of SOX17 expression is independent of methylation of the CpG island in its promotor region. HPV can be detected in SOX17‐positive immature metaplastic regions in the immediate vicinity of SOX2‐positive SIL, suggesting that switches in SOX17 and 2 expression can occur upon HPV infection. Conclusions This switch in expression, and the strong association between the distribution of reserve cells and squamous areas within the columnar epithelium in the TZ, suggests that reserve cell proliferations, next to basal cells in the squamous epithelium, are potential targets for the formation of squamous lesions upon viral infection.

A clearcut definition of the transition from the cervix to the lower uterine segment is lacking. We therefore evaluated the location of the anatomic border between the cervix and the uterine corpus. Using both morphometry and immunohistochemisty, we examined the epithelial and stromal cell types in this transition zone. In 26 patients, longitudinal sections from the cervix uteri up to the fundus uteri were paraffin embedded and immunohistochemically stained for BCL2, keratin 5, Ki-67, CD10, and CD34. Examination of the slides resulted in the identification of a junctional zone in the cranial portion of the cervix, which is characterized by a usually abrupt morphologic and immunohistochemical transition from an endocervical-type mucinous epithelium to a ciliated tubal-like epithelium and a slow transition in stromal marker expression patterns. This epithelial transition was characterized by its intense keratin 5 and BCL2 staining with accompanying Ki-67 expression in the tubal-like epithelium, whereas the endocervical epithelium was largely negative for these markers. CD10 expression was usually quite intense directly around endocervical invaginations, but the remaining stroma was negative. Toward the endometrial cavity, expression increased and endometrial stroma displayed full thickness expression for CD10. CD34 showed a reverse pattern to CD10, with moderate expression in the endocervical stroma, which disappeared in the endometrial stoma. The immunohistochemical identification of this transition may allow a more objective determination of the extension of endometrial carcinoma into the cervix in cases that are morphologically problematic. Furthermore, as ciliated tubal-like epithelium is invariably found cranial to the uterine-cervix-isthmus junction, a diagnosis of tubal metaplasia should not be made in this region and tubal-like epithelium is not indicative of a metaplastic process.