The number of general presentations at the annual meeting of the Japan Radiological Society was analyzed for the past five years. The number of general presentations from Japan averaged about 170 per year, and it was found that the number of presentations has been decreasing even taking into account the situation of the COVID-19 pandemic. The reasons for this are discussed.

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A man in his 60s was referred to our hospital for evaluation of a submucosal mass in the stomach incidentally found during upper gastrointestinal endoscopy at a regular medical checkup. An enhanced computed tomography (CT) scan showed a lobular, heterogeneously enhanced mass in the gastric fornix, and another round, heterogeneously enhanced mass was found in the mesentery. These masses showed FDG uptake on positron emission tomography CT and demonstrated low signal intensity on T1WI and heterogeneous intensity on T2WI. The patient underwent partial gastrectomy and colectomy and was diagnosed with multicentric dedifferentiated liposarcoma in the stomach and mesentery. Dedifferentiated liposarcoma is a variant of liposarcoma with a more aggressive course. It occurs most commonly in the retroperitoneum and rarely in other anatomic locations. In this report, we describe a case of dedifferentiated liposarcoma arising simultaneously from the stomach and mesentery. Multiple abdominal liposarcoma is an extremely rare entity. In dedifferentiated liposarcoma, the adipose component may not be identified on images, and preoperative diagnosis is difficult.

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A yolk sac tumor is a rare malignant germ cell tumor that typically originates from gonads, though it can arise from an extragonadal location. A rare case of an extragonadal yolk sac tumor in a 32-year-old woman with peritoneal and omental dissemination and liver metastases is reported. The patient’s serum AFP level was elevated. Contrast-enhanced computed tomography (CT) showed an enhanced mass in the posterior cul-de-sac with dilated internal vessels. On magnetic resonance imaging (MRI), flow voids were seen within the mass on T2-weighted imaging, and multiple peritoneal nodules and liver metastases were also evident. Pathological examination showed a yolk sac tumor, and chemotherapy was started. This case showed all four CT signs previously described as suggestive of yolk sac tumor: mixed solid-cystic nature, intratumoral hemorrhage, marked enhancement, and dilated intratumoral vessel. Yolk sac tumors are common in young women and are known for their chemosensitivity. Therefore, prompt diagnosis is important to allow prompt treatment. The combination of clinical and imaging findings contributed to the preoperative diagnosis of yolk sac tumor in the present case and allowed prompt treatment and a surgical plan.

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