Well-differentiated Noninvasive Neuroendocrine Tumor of the Breast in the Form of an Intracystic Tumor—Report of a Case—

Abstract

Neuroendocrine tumors of the breast are rare and have been reported to account for 0.08 - 0.8% of all breast tumors. Among of them, the tumor appeared in the form of an intracystic tumor has been reported in only four cases in Japan. We herein report a case of noninvasive neuroendocrine tumor of the breast in the form of an intracystic tumor presented with intracystic hemorrhage.

An 81-year-old woman was referred to our hospital because of a right breast tumor. The tumor with smooth surface and clear margin located in the AC area of the right breast was about 5.0 cm in size, elastic-soft and quite movable. Mammography showed a round high-density mass with an almost regular margin. Ultrasonography showed a circumscribed intracystic tumor measuring 20×10 mm. The intracystic tumor was irregular in shape, and continued with the cyst wall. Enhanced CT scan demonstrated a high density lesion in the cystic lesion. Aspiration biopsy revealed malignant cytology. Simple mastectomy was performed with a diagnosis of intracystic tumor. The cut surface of the resected specimen demonstrated a 10 × 20 mm intracystic tumor in the 50 × 55 mm cyst. The pathological diagnosis was noninvasive neuroendocrine tumor, well-differentiated, positive for estrogen receptor and progesterone receptor and negative for HER2. Most of the tumor cells were positive by synaptophysin and chromogranin A staining. The patient received hormone therapy with an oral aromatase inhibitor. The patient is doing well without metastases as of 5 years after the operation.