Case report: two cases of extremely rare primary pure squamous cell carcinoma of the breast

RATIONALE: Since primary pure squamous cell carcinoma of the breast is a rare disease, few reports describe the characteristic findings on performing preoperative imaging that can be used to distinguish it from normal breast cancer. The rapid evolution and lack of an established method of treatment has resulted in several reports of advanced cases of primary pure squamous cell carcinoma of the breast. PATIENT CONCERNS: Case 1 was a 44-year-old woman with an elastic, hard tumor in the left C region. Ultrasonographic analysis revealed a maximal 11-mm hypoechoic area. Histologically, the tumor was a well-differentiated squamous cell carcinoma with prominent keratinization, and there was prominent inflammatory cell infiltration, necrosis, and fibrosis. Case 2 was a 58-year-old woman with an elastic, hard tumor in the left C/D region. Ultrasonographic analysis revealed a maximal 31-mm hypoechoic area with partially calcified areas and a hyperechoic margin. Histologically, the tumor was a squamous cell carcinoma with prominent keratinization exhibiting an infiltrative growth pattern. The tumor had no connection to the epidermis and partially transitioned into the atypical ductal epithelium in the area surrounding the focus. DIAGNOSES: The patient in Case 1 was preoperatively diagnosed with T1cN0M0 Stage I cancer of the left breast, but both patients were finally diagnosed with T2N0M0 Stage IIA cancer. INTERVENTIONS: Case 1: left partial mastectomy and axillary lymph node dissection were performed. The patient was administered 4 courses of FEC100 and 4 courses of DTX as postoperative adjuvant therapy. Case 2: left modified radical mastectomy and axillary lymph node dissection were performed without any postoperative adjuvant therapy. OUTCOMES: Case 1: no sign of relapse was observed, but the patient moved away from the area to another hospital in March 2014 and eventually died due to relapse in January 2016. Case 2: four years after surgery, no relapse has been observed. LESSONS: We should always keep the presence of primary pure squamous cell carcinoma among breast cancers in mind although the crisis rate is very low. Due to its high malignancy, needle biopsy and aspiration biopsy cytology should be performed to make a definitive diagnosis.