Familial adenomatous polyposis （FAP） is caused by germline mutation of the APC gene. Desmoid tumors are found in 8-20% of patients with FAP. Present case was a 28 years old woman without a history of abdominal surgery. After diagnosis of FAP at 16 years old, she underwent periodic endoscopic polypectomy for colonic polyps and endoscopic submucosal dissection for mucosal gastric cancer. She visited our hospital with abdominal fullness. CT and MRI showed a large amount of ascites and 40mm-size cystic tumor near the left ureter and left hydronephrosis. We suspected gynecologic malignancy, desmoid tumor, or peritoneal cancer. Exploratory laparoscopy revealed massive urinary ascites with the retroperitoneal tumor involving the left ureter. We performed combined resection of the tumor and left ureter followed by ureteroureteral anastomosis. The tumor was pathologically diagnosed as a desmoid tumor. Desmoid tumor is known as one of the extraintestinal manifestations of FAP, but the case with urinary ascites is extremely rare.

　Hereditary breast and ovarian cancer (HBOC) caused by germline pathogenic variant in BRCA 1/2 gene is gaining considerable attention in recent years. Since BRCA1/2 pathogenic variant carriers are at extremely high-risk of developing breast and ovarian cancer, risk-reducing salpingo-oophorectomy (RRSO) and risk-reducing mastectomy (RRM) are recommended.

　In this report, we experienced an extremely rare case of familial breast cancer in an identical female twin pair. First one of twins developed breast cancer, followed by another of twins. The second case was suspected to be HBOC and was confirmed to be BRCA1 pathogenic variant positive, so that total mastectomy and contralateral RRM were indicated and performed.

　BRCA gene testing would be useful to determine the operative methods in case of suspected HBOC. We concluded that HBOC patients should be provided with sufficient information in advance, including the risk of developing breast and ovary cancer and the benefit of risk-reducing surgical procedures.

　In July 2018, Olaparib, a poly adenosine diphosphate ribose polymerase（PARP）inhibitor, was indicated for patients with HER2-negative BRCA pathogenic variant-positive metastatic breast cancer. At the same time, BRCA genetic testing was approved as companion diagnostics to determine whether olaparib can be used as a treatment for breast cancer. By April 2019, 38 BRCA genetic tests had been performed at our hospital, and seven of these had confirmed pathogenic variants. Five patients were treated with olaparib and achieved therapeutic effects. These effects did not depend on the number of regimens before the treatment with Olaparib. However, in some cases, the treatment period lasted for >1 year, and other cases had progressive disease（PD）within about 6 months. Although side effects such as progression of anemia and gastrointestinal symptoms have been reported, they were within the manageable range in our cases. Since therapeutic effects are expected with a few side effects， genetic testing should be performed on candidate patients. However, not all patients have long-term therapeutic effects, therefore, treatment other than olaparib should be considered.

　Our genetic counseling service has started since 2016, where the certified genetic counselors have been conducting a family history taking and risk assessment to screen hereditary breast and ovarian cancer (HBOC) for all the breast cancer patients undergoing surgery.

The family histories were taken from 306 patients between November, 2016 and December, 2018, 94 patients met at least one of the criteria in NCCN guideline. Then, the genetic counselor returned the results of the risk assessment to 94 patients. Thirty-four patients out of 94, who met the more than one NCCN criteria or were assessed as high risk by using algorithms for HBOC (Prevalence Table, Myriad, or BRACAPRO) screening, were provided the information about the genetic counseling as HBOC follow-up group. Finally, 3 patients took the genetic counseling sessions with us.

Our approach provided clinicians and the other medical staffs good opportunities to share the understanding of HBOC, leading to the follow-up of the patients continuously in cooperation with each specialized department.

　Genomic and genetic health care is increasingly available in clinical practice. Since genetic services should play significant roles in preventive medicine as well, we established in Oct. 2015 the division of clinical genetics to effectively and carefully provide genetic services in the Chiba Foundation for Health Promotion and Disease prevention (CFHD), a non-profitable organization for health checkup and cancer screening for inhabitants and workers in Chiba prefecture. As a first step, we have tried to pick up subjects with hereditary tumors using cancer family history questionnaire among those having cancer screening and also through referrals of suspected cases from nearby hospitals. As of September 30, 2020, we have found five cases of Lynch syndrome and 4 cases of hereditary breast and ovarian cancer syndrome confirmed by genetic testing. Since cancer screening of multiple organs are well organized at CFHD, we have provided cancer screening and surveillance programs for their relatives as well. We are going to pursue “individualized cancer screening” based on genetic risk together with appropriate genetic counselling.