1.On determining the origin of high-grade plasmacytoma 1.With BRCA1/2 mutation, it mostly comes from the epithelium of the umbilical end of the fallopian tube; 2.Disseminated high-grade plasmacytoma may originate from: the mesothelium of the ovarian surface sagging; ovarian cortical inclusion cyst, epithelial ectopic of the fallopian tube of the ovary. 3. Some of them may still originate from the peritoneum (so-called second müllerian system). 2. To determine whether it is ovarian primary? Peritoneal primary or tubal primary? It is usually an arbitrary judgment by the pathologist, which mainly depends on the distribution of the main body of the tumor. 1.If the main body of cancerous tissue is located in ovarian cortex, with less involvement of peritoneum and oviduct, it can be diagnosed as ovarian cancer; 2.If the lesion mainly involves the fallopian tube, especially if there is BRCA1/2 mutation, the diagnosis of fallopian tube cancer; 3.If there is no lesion in ovary, or only involves ovarian surface, or a small amount involves superficial ovarian cortex, while most of the lesion is located in peritoneal cavity, the diagnosis is considered as peritoneal primary high-grade plasmacytoma 4.If there is cancer everywhere such as ovary, fallopian tube and peritoneum, which cannot be judged, the diagnosis is pelvic peritoneal cavity high-grade plasmacytoma with indeterminate primary site. III. What about clinical staging? In 2014, the International Federation of Gynecology and Obstetrics (FIGO) updated the clinical staging criteria for ovarian, fallopian tube and peritoneal cancers and combined them, i.e., there are no longer separate staging criteria for fallopian tube and peritoneal cancers. As long as the lesion involves the fallopian tube or peritoneum, it is at least stage II. Therefore, regardless of the primary site of diagnosis, it does not affect clinical management. Nevertheless, pathologists try to provide the primary site. The pathologist should also provide the following information when making the diagnosis: 1. the histological type of the tumor; 2. the histological grading of the tumor; 3. whether the cytology of ascites and peritoneal washings is positive; 4. the lymph node metastasis and its location; 5. the size of the lymph node metastasis is closely related to the staging, so the size of the lymph node metastasis is provided.