A 65-year-old female patient was admitted to the hospital with a sudden painless lump in her right breast for 15 days. History: 15 days ago, the patient was sleepy after a day of labor and fell asleep after drinking 500 ml of white wine at dinner. The next morning, she found a lump in the lower part of the right outer breast, about the size of a duck egg, with edematous, non-red, painless skin in the nipple-areola area and an itching sensation. On the 5th day, she was seen at the local county hospital and given intravenous penicillin anti-inflammatory treatment for 1 week, which was ineffective. The lump seemed to increase in size and harden, so she was suspected of having breast cancer and came to our hospital. On examination, the right breast was larger than the left, and the nipple-areola area was edematous, about 5*4 cm in extent, especially in the area below the nipple, and the orange peel sign was visible. A 6*5 cm mass with poorly defined borders, heterogeneous texture and moderate firmness could be seen at 7-9 points on the right side of the breast. The dimple sign due to pulling of Cooper’s ligament was seen when the skin above the mass was tensed. The mass was movable without pressure pain. A 1.0 cm lymph node was found in the right axilla, which was soft, mobile and without pressure. No abnormality was found in the left breast. The left axillary fossa and bilateral supraclavicular lymph nodes were not enlarged. Mammogram: 5*3cm high-density shadow in the outer lower quadrant of the right breast with partial border indistinctness, skin thickening in the right areola area, and lymph nodes in the right axilla were seen. Ultrasound examination of the mammary gland showed a cystic solid mass of 5*4 cm in the right breast at 9 o’clock with still clear borders and an envelope, and no blood flow signal was seen on CDFI. Lymph nodes were seen in the right axilla, the large one was about 1.2*0.4cm with envelope.BI-RADS grade 4. After admission, a combination of hollow needle aspiration biopsy and surgery after neoadjuvant chemotherapy was originally planned. However, considering the possibility that hollow needle aspiration might cause outflow of cystic fluid and the possibility of difficulty in pathological diagnosis due to low tissue acquisition, the preoperative examination also revealed the presence of thrombocytosis, and bone marrow aspiration was performed to diagnose primary thrombocytosis. Therefore, the treatment plan was changed to correct the thrombocytosis and then operate first, and then decide the subsequent treatment according to the pathological staging. The platelets decreased from 1338/mm2 to 700/mm2 after 1 week of oral administration of hydroxyurea 90 mg/day. During this period, the edema in the areola of the right nipple gradually decreased, the lump increased in mobility, the dimple sign on the surface disappeared, and the boundaries of the lump became clearer than at the time of admission. The right breast mass was then excised under local anesthesia. Intraoperatively, a 5*4 cm mass was seen in the subcutaneous fat and gland of the right breast with clear borders, and the gland was partially enveloped, while vascular-like structures were seen in the fat layer and the envelope was not obvious. Initially, it was thought to be a subcutaneous hematoma caused by local anesthesia, and the hematoma and mass were completely excised along with 2-3 mm of glandular tissue surrounding the mass and sent for intraoperative cryopathology, which was reported as a hemangiolymphangioid tumor of the breast. Postoperative treatment of primary thrombocytosis was continued with the addition of aspirin 100 mg/day orally in addition to hydroxyurea to prevent thrombosis. Postoperative paraffin pathology determined a right breast angiolymphoma. Lymphangioleioma is not a true tumor, but a benign congenital malformation. It is a tumor-like malformation that occurs after the isolation of the primitive lymphatic sac from the lymphatic system in some parts of the embryonic development, and consists of proliferated, dilated, and structurally disordered lymphatic vessels. According to the pathology and clinical manifestations, there are three types of lymphoma: capillary lymphoma, cavernous lymphoma and cystic lymphoma. About 3/4 of them are cystic lymphangiectasia, also known as cystic hydatid tumor. About 1/3 of lymphangioleiomas occur in the neck, followed by the axilla and groin, and rarely in the mesentery, retroperitoneum, pelvis, mediastinum, oral and maxillofacial region, and bone, etc. Rarely, they occur in the breast. Lymphangioleiomas often contain one or more cysts of different sizes, which are not connected to the nearby lymphatic system. Most cystic lymphangioleiomas are due to abnormal development of the lymphatic system and failure of communication between the lymphatic system and the venous system. According to the etiology and pathogenesis, they can be divided into: (1) Congenital cystic lymphangioleiomas: they develop from abnormal development of primitive lymphatic vessels and isolated leftover embryonic lymphoid tissue, and are round, oval or lobulated cysts with a large amount of lymphatic fluid inside. (2) Acquired or secondary cystic lymphangioleiomas: they appear longer after birth and form as cysts due to acute or chronic expansion secondary to inflammatory reactions or other diseases causing lymphangioleiitis, local fibrous tissue hyperplasia or various true tumors causing pressure and obstruction of lymphatic vessels. The lymphatic vessels of the adult breast originate from the interlobular connective tissue and the ductal wall of the milk ducts. These connect with their superficial subcutaneous lymphatic plexus, especially around the nipple, and then drain into the axilla. Cystic lymphadenoma of the breast shows a round or lobulated density shadow on mammography and a multiple cystic mass on ultrasound imaging, with a cystic solid component consisting of cystic walls and septa of varying thickness. Lymphangioadenoma of the breast needs to be differentiated from simple breast cysts: the former are often larger in size and can increase suddenly, often occurring in typical sites such as the tail of Spence. Fine needle aspiration cytology is useful in the diagnosis of lymphangioleioma. The cystic fluid of lymphangioleioma is clear and yellowish with few cells other than a few lymphocytes. In contrast, simple breast cysts whose cyst fluid is often cloudy yellow or yellow-green, or rarely colorless, clear breast cysts are acellular or have a relatively limited number of epithelial cells. This includes parietal pulp secretion and foam cells. Surgical excision is the treatment of choice. Sclerosing injections, incision and drainage, and radiation therapy have been reported to be ineffective.