A Case of Giant Borderline Phyllodes Tumor of the Breast Associated with Hypoglycemia

We report a patient with a giant phyllodes tumor of the right breast associated with a hypoglycemic attack. A 48-year-old woman experienced a loss of consciousness and was transferred via ambulance to our hospital emergency department. Upon arrival, her blood glucose level was 26 mg/dl, and a giant tumor (>20 cm in diameter) with skin ulceration was observed on the right breast. Core needle biopsy led to a histological diagnosis of a phyllodes tumor of the breast. Ultrasonography and computed tomography detected neither distant metastasis nor a pancreatic endocrine tumor. Her preoperative serum insulin-like growth factor (IGF)-II and insulin levels were 1,330 ng/ml (normal range, 519-1067 ng/ml) and <1.0 µU/ml, respectively. Following a simple mastectomy, the 24-h postoperative serum IGF-II and insulin levels were 496 ng/ml and 10.0 µU/ml, respectively. The IGF-II levels detected in the phyllodes tumor and normal breast tissue were 10,600 ng/Wg (wet weight in grams) and 855 ng/Wg. We conclude from these findings that the hypoglycemic attack was related to the elevated IGF-II level in the giant phyllodes tumor of the breast.