Human papilloma virus (HPV) infection causes cancers and their precursors (high grade squamous intraepithelial lesions) near cervical and anal squamocolumnar junctions. Recently described cervical squamocolumnar junctions cells are putative residual embryonic cells near the cervical transformation zone. These cells appear multipotential and share an identical immunophenotype (strongly CK7-positive) with over 90% of high grade squamous intraepithelial lesions and cervical carcinomas. However, because the number of new cervical cancers discovered yearly world-wide is 17-fold that of anal cancer, we posed the hypothesis that this difference in cancer risk reflects differences in the transition zones at the two sites. The microanatomy of the normal anal transformation zone (n = 37) and topography and immunophenotype of anal squamous neoplasms (n = 97) were studied. A discrete anal transition zone was composed of multi-layered CK7-positive/p63-negative superficial columnar cells and an uninterrupted layer of CK7-negative/p63-positive basal cells. The CK7-negative/p63-positive basal cells were continuous with – and identical in appearance to - the basal cells of the mature squamous epithelium. This was in contrast to the cervical squamocolumnar junction, that harbored a single-layered CK7-positive/p63-negative squamocolumnar junction cell population. Of the 97 Anal intraepithelial neoplasia/squamous cell carcinomas evaluated, only 27% (26/97) appeared to originate near the anal transition zone and only 23% (22/97) were CK7-positive. This study thus reveals two fundamental differences between the anus and cervix: 1) the anal transition zone does not harbor a single monolayer of residual un-differentiated embryonic cells and 2) the dominant tumor immuno-phenotype is in keeping with an origin in metaplastic (CK7-negative) squamous rather than squamocolumnar junction (CK7-positive) epithelium. The implication is that at birth, the embryonic cells in the anal transition zone have already begun to differentiate, presenting a less vulnerable squamous metaplasia that - like vaginal and vulvar epithelium - is less prone to HPV directed carcinogenesis. This in turn underscores the link between cancer risk and a very small and discrete population of vulnerable squamocolumnar junction cells in the cervix.

The oviducts contain high grade serous cancer (HGSC) precursors (serous tubal intraepithelial neoplasia or STINs), which are γ-H2AXp- and TP53 mutation-positive. Although they express wild type p53, secretory cell outgrowths (SCOUTs) are associated with older age and serous cancer; moreover both STINs and SCOUTs share a loss of PAX2 expression (PAX2n). We evaluated PAX2 expression in proliferating adult and embryonic oviductal cells, normal mucosa, SCOUTs, Walthard cell nests (WCNs), STINs and HGSCs, and the expression of genes chosen empirically or from SCOUT expression arrays. Clones generated in vitro from embryonic gynecologic tract and adult fallopian tube were Krt7p/PAX2n/EZH2p and underwent ciliated (PAX2n/EZH2n/FOXJ1p) and basal (Krt7n/EZH2n/Krt5p) differentiation. Similarly non-ciliated cells in normal mucosa were PAX2p but became PAX2n in multilayered epithelium undergoing ciliated or basal (Walthard cell nests or WCN) cell differentiation. PAX2n SCOUTs fell into two groups; Type I were secretory or secretory/ciliated with a “tubal” phenotype and were ALDH1n and β-cateninmem (membraneous only). Type II displayed a columnar to pseudostratified (endometrioid) phenotype, with an EZH2p, ALDH1p, β-cateninnc (nuclear and cytoplasmic), stathminp, LEF1p, RCN1p and RUNX2p expression signature. STINs and HGSCs shared the Type I immunophenotype of PAX2n, ALDH1n, β-cateninmem, but highly expressed EZH2p, LEF1p, RCN1p, and stathminp. This study, for the first time, links PAX2n with proliferating fetal and adult oviductal cells undergoing basal and ciliated differentiation and shows that this expression state is maintained in SCOUTs, STINs and HGSCs. All three entities can demonstrate a consistent perturbation of genes involved in potential tumor suppressor gene silencing (EZH2), transcriptional regulation (LEF1), regulation of differentiation (RUNX2), calcium binding (RCN1) and oncogenesis (stathmin). This shared expression signature between benign and neoplastic entities links normal progenitor cell expansion to abnormal and neoplastic outgrowth in the oviduct and exposes a common pathway that could be a target for early prevention.

The origins of pelvic high grade serous cancer (HGSC) have become a subject of intense scrutiny in view of proposals to reduce the incidence of the disease via opportunistic salpingectomy in healthy women. Accumulated data implicates the fimbria as a site of origin and descriptive molecular pathology and experimental evidence strongly support a serous carcinogenic sequence in the fallopian tube. Both direct and indirect ("surrogate") precursors suggest the benign tube undergoes important biologic changes after menopause, acquiring abnormalities in gene expression that are shared with malignancy. However, the tube can be linked to only some HGSCs, recharging arguments that nearby peritoneum/ovarian surface epithelium (POSE) also hosts progenitors to this malignancy. A major sticking point is the difference in immunophenotype between POSE and Müllerian epithelium, essentially requiring mesothelial to Müllerian differentiation prior to or during malignant transformation to HGSC. However, there is emerging evidence that an embryonic or progenitor phenotype exists in the adult female genital tract with the capacity to differentiate, normally or during neoplastic transformation. Recently, a putative cell of origin to cervical cancer has been identified in the squamo-columnar (SC) junction, projecting a model whereby embryonic progenitors give rise to immuno-phenotypically distinct neoplastic progeny under stromal influences via "top down" differentiation. A similar pattern of differentiation is implied in the endometrium and the juxtaposition of disparate epithelial immuno-phenotypes (POSE and underlying Müllerian inclusions) recapitulates this in the ovary. While a sudden mesothelial-Mullerian transition remains to be proven, it would explain the rapid evolution, short asymptomatic interval, and absence of a defined epithelial starting point in many HGSCs. Resolving this question will be critical to both expectations from prophylactic salpingectomy and future approaches to pelvic serous cancer prevention.