[A Case of Breast Pleomorphic Invasive Lobular Carcinoma with Difficulty in Preoperative Diagnosis].

Invasive lobular carcinoma of the breast is on the rise. Among lobular carcinomas, pleomorphic invasive lobular carcinoma is considered to be a highly malignant subgroup. The patient was a 38-year-old woman. A health check revealed a tumor in her left breast and she visited our department. On arrival, a mobile mass of about 20 mm in diameter was physically palpable in the AB area of the left breast. Mammography showed it as a focal asymmetric density. An ultrasonography showed it as a hypoechoic mass with an unclear border. A contrast-enhanced MRI showed it as a mass of about 20 mm with contrast. Core needle biopsy revealed the diagnosis of invasive lobular carcinoma. There was no distant metastasis, so muscle-sparing mastectomy and sentinel lymph node biopsy were performed. Pathological examination of the resected specimen revealed the diagnosis of pleomorphic invasive lobular carcinoma, tumor diameter 40 mm, resection margin negative, ER positive, PgR positive, HER2(1+), Ki-67 17.2%. After chemotherapy, the patient was followed up with LH-RH agonist and tamoxifen. At present, 1 year and 6 months after surgery, there has been no clear evidence of metastasis or recurrence.