Angiosarcoma of the breast is a relatively rare tumor of high malignancy originating from the perilobular or lobular capillaries of the breast. Three cases were admitted to our hospital in the past 15 years and are reported as follows. 1. Clinical data Case 1: Patient, female, 27 years old, married. She was admitted to the hospital on May 10, 1996 due to a mass found in the left breast, which had been rapidly increasing in size for 2 months. On examination, there was a cyanotic surface swelling in the upper outer quadrant of the left breast, about 5 cm × 6 cm × 3 cm in size, with soft texture, poorly defined borders, no pressure pain, no overflow from the nipple when squeezed, no enlarged lymph nodes in the bilateral axillae and clavicles, and no abnormalities in the contralateral breast. Infrared scan showed a 5cm×6cm shadow in the upper outer quadrant of the left breast, with richly disorganized, thickened, gross, and pseudo-footed vessels. The lump was punctured with dark red viscous hemorrhagic fluid, and cytological examination diagnosed malignant tumor. Surgery was performed under general anesthesia. Intraoperative fast wax pathology report: malignant tumor of the left breast, so modified radical mastectomy for breast cancer was performed. Pathology report: left breast hemangiosarcoma. Six courses of chemotherapy with CAF regimen were given and the patient was followed up for 3.5 years. Case 2: Female, 23 years old, unmarried. A rapidly enlarging mass in the left breast was found for 3 months and she was admitted to the hospital on March 13, 2007. In December 2005, the patient underwent a lumpectomy in a local hospital for a mass in the left medial mammary gland, and the postoperative pathology report showed a hemangioma of the breast. On examination: 8cm×6cm×5cm sized mass on the left medial mammary gland, with a greenish-purple surface, hard texture, unclear border, and no adhesion to the pectoralis major muscle and skin. There was no blood spillage when the nipple was squeezed. No enlarged lymph nodes were found in the bilateral axillae and supraclavicular region. There was no abnormality in the contralateral breast. Ultrasound of the breast showed a substantial non-homogeneous mass in the left breast without envelope and rich blood flow. On March 16, 2007, a regional left mastectomy was performed under epidural anesthesia. A rapid intraoperative section suggested “possible left mammary angiosarcoma”, and left mastectomy was performed. Postoperative pathology report: left breast hemangiosarcoma. He died of multiple metastases in the liver and lung 7 months after surgery. Case 3: Female, 29 years old, married. She was admitted to the hospital on April 9, 2009 after bilateral breast enlargement and swelling was found for six months 1 year after breastfeeding. She had been diagnosed with breast enlargement and bruised breast, and the symptomatic treatment was poor. On examination: the bilateral mammary glands were asymmetrically enlarged, especially on the right side, and the skin was shiny. The nipples and medial skin of the right mammary gland were purplish red in an area of about 6 cm × 3 cm, soft in texture, and the volume could be reduced when squeezed hard. Color ultrasonography: huge mixed echogenicity in bilateral breast glands, only a little glandular structure remained, and there were scattered irregular lamellar and striated moderately strong echogenicity and honeycomb anechoic; bilateral axillary lymph nodes were not enlarged. Diagnosis: bilateral mammary hemangioma, bilateral mastectomy was performed under general anesthesia. Pathology report: bilateral mammary angiosarcoma, grade I on the right side and grade II on the left side; local skin and nipple infiltration on the right side. Immunohistochemical examination CD34 (+) Ki67 (_), recurrence in the chest wall and skin metastasis in the shoulder and abdomen started six months after surgery, all of which were locally resected, with a total of 9 local resections for recurrence or metastasis, and 2.5 years of follow-up were alive and well, and no liver or lung metastasis was found. 2, Discussion Hemangiosarcoma of the breast, also known as angioendothelial sarcoma of the breast, is a rare malignant tumor of mesenchymal system origin. it was first described by Schmidt in 1887, and no large number of cases have been reported so far. The incidence of this disease is low, accounting for approximately 0.03% to 0.04% of breast tumors and 8% of all breast sarcomas as reported in the literature. More than 200 cases have been reported, and bilateral simultaneous occurrence is extremely rare, with more than 10 cases reported in domestic and foreign literature. It can occur at any age, but mostly occurs in young women aged 20-30. The pathogenesis is not clear, but mostly occurs in women during pregnancy and lactation, and its onset may be related to high estrogen levels. The three cases in this group were all female, aged 23-29 years, with three cases in lactation and two cases unmarried. Two of the cases occurred in the left breast, and one case had bilateral simultaneous onset, which is very rare. The first symptom of the disease is a rapidly enlarging mass, painless or painful, with a few cases of diffuse enlargement of the breast or persistent subcutaneous hemorrhage; the masses are on average 5 cm in diameter, located in the parenchyma of the breast, soft, with indistinct borders, and the skin surface may be red or cyanotic if superficially located, a sign considered characteristic of primary angiosarcoma of the breast. This sign is thought to be characteristic of primary angiosarcoma of the breast. Imaging is often not specific, but can reflect the size, extent, and degree of infiltration of the tumor. Because mammography and ultrasonography are not characteristic, they are easily diagnosed as breast hyperplasia, bruised breast disease, trauma, chronic inflammation, benign breast tumor or breast cancer. MRI, especially dynamic MRI, has qualitative diagnostic value for this disease and helps to clearly show the extent and characteristics of the lesion. The pathological pattern of angiosarcoma of the breast is diverse and needs to be differentiated from other lesions of the breast: well-differentiated angiosarcoma of the breast should be differentiated from benign hemangioma and papillary vascular endothelial cell hyperplasia; low-differentiated angiosarcoma of the breast should be differentiated from breast cancer and angiosarcoma-like metaplastic breast cancer. Immunohistochemistry is important for the diagnosis and differential diagnosis of hemangiosarcoma. Studies have shown that the positive rate of endothelial cell marker antigen FVIIIAg is as high as 41%~100% in angiosarcoma cells, which has diagnostic value for this disease. Compared with CD34, CD31 has the same sensitivity and is more specific than CD34. Surgery is currently considered to be the only effective treatment, and mastectomy or simple mastectomy margins can be performed, while paying attention to the tumor margins, and axillary lymph node dissection is generally not advocated. There is no uniform standard whether to adjuvant radiotherapy or chemotherapy after surgery. The therapeutic effect of chemotherapy on angiosarcoma of the breast has not been confirmed for many years. Previously, it was believed that chemotherapy, like radiotherapy, could not alter its clinical course. However, some studies have shown a positive effect of adjuvant chemotherapy for angiosarcoma of the breast. Recent studies have shown that doxorubicin has a strong inhibitory effect on tumor proliferation in angiosarcoma and may be a novel drug for the treatment of angiosarcoma. The disease is extremely malignant, prone to recurrence, and can metastasize widely via blood circulation at an early stage. It can metastasize to lung, skin and subcutaneous tissue, bone, liver, brain, ovary and contralateral breast, etc. Rarely, it metastasizes to the eye. Histologic grading of the tumor is an important factor in determining prognosis, and except for highly differentiated angiosarcoma, other types usually have a poor prognosis. The overall survival rate varies widely among reports, with a general 3-year survival rate of 38% and a 5-year survival rate of about 33%. The average survival time reported abroad is 22 months, and the 5-year survival rate is only 21%. Tumor tissue grading is an important factor in determining prognosis, and the 5-year survival rate of patients with highly differentiated tumors is as high as 91%, while that of those with intermediate and low differentiation is only 68% and 14%. In our group, except for case 1, which was followed up for three and a half years without recurrence, the other two cases recurred or metastasized within six months, and all of them were actively operated again after local recurrence, and case 3 was reissued after surgery with local excision as many as nine times. In conclusion, hemangiosarcoma of the breast is a relatively rare and highly malignant tumor in clinical practice. Metastases to various organs of the body, such as liver and lung, can occur at an early stage, and local recurrence is easy. Therefore, we should be familiar with its clinicopathological features and master its diagnostic criteria to achieve early diagnosis and early treatment as much as possible in order to prolong the survival of patients and improve the cure rate.