A Case of a Rapidly Growing Granulocyte Colony-Stimulating Factor-Producing Squamous Cell Carcinoma of the Breast.

A 34-year-old woman with a rapidly growing right breast mass visited our hospital. The mass was diagnosed as a right breast cancer (cT3N1M0 stage ⦀A). Her serum leucocyte count and C-reactive protein levels were high, and she had persistent fever. However, serum procalcitonin and β-D-glucan levels were normal, and no apparent infection focus was detected, although her serum granulocyte colony-stimulating factor (G-CSF) level was markedly elevated to 42.7 pg/mL. Therefore, a G-CSF-producing breast cancer was suspected. A pathological analysis of the surgical specimen revealed a squamous cell carcinoma of the breast (pT2N0 [i+] M0 stage ∥A). Right mastectomy (with the resection of the pectoralis major muscle), axillary lymph node dissection, and split layer grafting were performed. The leucocyte count and serum G-CSF level decreased on postoperative day (POD) 1 and normalized on POD 6. As adjuvant chemotherapy, 4 cycles of a combination chemotherapy with adriamycin and cyclophosphamide and 12 cycles of weekly paclitaxel were administered. After chemotherapy, the patient also underwent postmastectomy radiotherapy. Currently, 30 months after surgery, the patient is alive and well with neither progression nor distant metastasis. G-CSF-producing breast cancers tend to rapidly grow such as in the current case; thus, surgery should be performed immediately, followed by appropriate adjuvant treatment.