[Morphologic features of fallopian tubal epithelium in pelvic high-grade serous carcinoma]

Objective: To study the pathologic features of fallopian tubal epithelium in patients with pelvic high-grade serous carcinoma (HGSC), to investigate its role in pelvic serous carcinogenesis and to reclassify the primary site of HGSC based on recently proposed criteria. Methods: The fallopian tubes in 58 cases of pelvic HGSC (54 cases of ovarian primary, 3 cases of tubal primary, 1 case of peritoneum) and 25 cases of pelvic non-HGSC (5 cases of ovarian low-grade serous cancer, 9 cases of endometrioid cancer, and 11 cases of clear cell ovary carcinoma) were collected from June 2015 to December 2016, and serially examined under light microscope (SEE-FIM protocol). Immunostaining for p53 and Ki-67 was performed to evaluate the presence of p53 signature, serous tubal intraepithelial lesion (STIL), serous tubal intraepithelial carcinoma (STIC) and invasive carcinoma in these fallopian tubes. Meanwhile, primary site of HGSC based on the recently proposed diagnostic criteria were also reclassified. Results: Among the study group, the frequencies of p53 signature, STIL, STIC and invasive HGSC were 27.6% (16/58), 43.1% (25/58), 36.2% (21/58) and 67.2% (39/58), respectively, while in control group, the proportions were 24.0% (6/25), 0, 0 and 8.0% (2/25), respectively. The continuum of epithelial changes in the process of serous neoplasia including p53 signature, STIL, STIC and invasive carcinoma was identified in 8 cases of pelvic HGSC. The proportions of STIL, STIC and invasive carcinomas in HGSC group were higher than that in non-HGSC group (P<0.01). About 80.0% (20/25) of STIL and 85.7% (18/21) of STIC were present unilaterally. Diagnostically, the study group contained the 17 cases of ovarian HGSC, 40 cases of tubal HGSC, and 1 case of peritoneal HGSC after reclassification of the cancer primary. Conclusions: Continuous changes of tubal epithelium including p53 signature, STIL, STIC and invasive carcinomas are identified in patients with HGSC, supporting the current understanding that the fallopian tube is likely the cellular source of the majority HGSC. STIL and STIC may be specific to pelvic HGSC and may act as a target for future research on the early detection and prevention of this disease. The newly proposed diagnostic criteria for pelvic HGSC will lead us to more accurate classification of cancer primary sites. Correct classification of HGSC may have potential impacts for cancer prevention and improve our understanding of ovarian serous carcinogenesis.