We conducted comprehensive integrative molecular analyses of the complete set of tumors in The Cancer Genome Atlas (TCGA), consisting of approximately 10,000 specimens and representing 33 types of cancer. We performed molecular clustering using data on chromosome-arm-level aneuploidy, DNA hypermethylation, mRNA, and miRNA expression levels and reverse-phase protein arrays, of which all, except for aneuploidy, revealed clustering primarily organized by histology, tissue type, or anatomic origin. The influence of cell type was evident in DNA-methylation-based clustering, even after excluding sites with known preexisting tissue-type-specific methylation. Integrative clustering further emphasized the dominant role of cell-of-origin patterns. Molecular similarities among histologically or anatomically related cancer types provide a basis for focused pan-cancer analyses, such as pan-gastrointestinal, pan-gynecological, pan-kidney, and pan-squamous cancers, and those related by stemness features, which in turn may inform strategies for future therapeutic development.

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Proposed origins of pelvic serous carcinoma include the ovary, fallopian tube, and peritoneum. Prophylactic salpingo-oophorectomies in BRCA+ women have recently identified the fimbria as a site of origin for early serous carcinoma (tubal intraepithelial carcinoma or TIC). We explored the relationship of TIC to pelvic serous carcinomas in consecutive cases with complete adnexal exam (SEE-FIM protocol). Cases positive (group A) or negative (group B) for endosalpinx (including fimbria) involvement, were subclassified as tubal, ovarian, or primary peritoneal in origin. Coexisting TIC was recorded in group A when present and p53 mutation status was determined in 5 cases. Of 55 evaluable cases, 41 (75%) were in group A; including tubal (n = 5), peritoneal (n = 6), and ovarian (n = 30) carcinomas. Foci of TIC were identified in 5 of 5, 4 of 6, and 20 of 30, respectively. Ninety-three percent of TICs involved the fimbriae. Five of 5 TICs and concurrent ovarian carcinomas contained identical p53 mutations. Thirteen of 14 cases in group B were classified as primary ovarian carcinomas, 10 with features supporting an origin in the ovary. Overall, 71% and 48% of "ovarian" serous carcinomas had endosalpinx involvement or TIC. TIC coexists with all forms of pelvic serous carcinoma and is a plausible origin for many of these tumors. Further studies are needed to elucidate the etiologic significance of TIC in pelvic serous carcinoma, reevaluate the criteria for tubal, peritoneal, and ovarian serous carcinoma, and define the role of the distal tube in pelvic serous carcinogenesis.

A proportion of adenocarcinomas in prophylactic adnexectomies (bilateral salpingo-oophorectomies [BSOs]) from women with BRCA mutations (BRCA positive) occur in the fallopian tube. We analyzed a consecutive series of BSOs from BRCA-positive women following an index case of fimbrial serous carcinoma. To determine if the fimbria is a preferred site of origin, we followed a protocol for Sectioning and Extensively Examining the FIMbria (SEE-FIM). Immunostaining for p53 and Ki-67 was also performed. Thirteen BRCA-positive women (cases) and 13 women undergoing BSOs for other disorders (controls) were studied. Tubal carcinoma was detected in 4 cases at the initial histologic evaluation and in no controls. A fifth carcinoma was discovered following further sectioning of the fimbriae. Three were BRCA2 positive and two BRCA1 positive. Three were in the fimbria, one in both the fimbria and proximal tube, and one involved the ampulla. Four were serous carcinomas, four were confined to the tube, and three were noninvasive (intraepithelial). No ovarian carcinomas were identified. All tumors were Ki-67 positive (>75% of cell nuclei), and excluding one endometrioid carcinoma, p53 positive (>75% cell nuclei); p53 positivity in the absence of elevated Ki-67 did not correlate with morphologic neoplasia. The fimbria was the most common location for early serous carcinoma in this series of BRCA-positive women. Protocols that extensively examine the fimbria (SEE-FIM) will maximize the detection of early tubal epithelial carcinoma in patients at risk for ovarian cancer. Investigative strategies targeting the fimbriated end of the fallopian tube should further define its role in the pathogenesis of familial and sporadic ovarian serous carcinomas.