A female patient aged 45 years was admitted to the hospital with a primary complaint of a left breast mass present for 6 months. The patient was a farmer without family history and didn't receive other treatment before. The mass increased rapidly in the past 3 months, reaching the size of a basketball with local skin ulceration and infection. The mass (25 cm in diameter) made the breasts asymmetric and was observed in the left breast with tough texture and poor mobility. The surface of the mass is uneven with skin ulceration. Bilateral axillary lymph nodes were not touched. Examination by magnetic resonance imaging showed that the solid mass had not invaded the chest wall muscle ( Figure 1 ). On the second and third day of admission, she experienced fasting hypoglycemia associated with fatigue, cold sweats, and confusion. Blood examination showed severe hypoglycemia (0.78 mmol/L), hypoinsulinemia (<1.39 pmol/L), and C peptide level (0.01 nmol/L). The serum insulin antibody was negative and the patient didn't take sulfonylureas previously. The level of carcinoembryonic antigen (CEA), alpha fetoprotein(AFP) and carbohydrate antigen153 (CA153) were within the normal range. The unenhanced magnetic resonance scan showed a regular pancreas and liver contour. Hence, the presence of islet cell tumor and hepatocellular carcinoma (hepatocellular carcinoma often lead to NICTH) were ruled out, and symptomatic treatments (e.g., intravenous infusion of 10% glucose solution) were administered to regulate the concentration of blood glucose. After symptomatic treatments, the symptoms above completely relieved. A comprehensive assessment of patient signs, clinical manifestations, medical history, auxiliary examinations, and preoperative puncture pathology considered the possibility of PTs. On August 27, 2020, the patient underwent left mastectomy. Intraoperative frozen section diagnosis revealed a fibroepithelial tumor, and the possibility of PT was not excluded. The upper, lower, inner, and outer edges of skin samples were submitted for examination, and there were no tumor cells found. The breast incision flap was sutured without axillary lymph node dissection. Immunohistochemical stains with antibodies against IGF-2 (IGF-2 Rabbit pAb A2086, dilution 1:300), CKpan (RAB-0050, dilution 1:200), SMA (alpha smooth muscle actin Rabbit pAb A7248, dilution 1:200) and Desmin (DES Rabbit pAb A0699, dilution 1:200) were performed. Postoperative immunohistochemical staining results ( Figure 2 ) were as follows: IGF-2(+), CKpan (+), SMA (+), Desmin (+). Postoperative paraffin pathology analysis (left breast) showed that the mass was borderline PT, part of the epithelium was squamous, and surface skin ulcers were formed (tumor diameter: 25 cm). The patient recovered well after the operation, and blood glucose and insulin levels returned to normal. No adjuvant therapy was administered after surgery and there was no tumor recurrence or metastasis detected at 3-month follow-up. The patient's family has signed the written consent.