HER-2 Heterogeneity in Breast Cancer: A Case Study

CASE The patient is a 75 year-old female with a history of stage 1 invasive ductal carcinoma of the left breast measuring 1.2 cm. Core biopsy of the mass demonstrated Nottingham grade 3 invasive ductal carcinoma; ER negative, PR negative, HER-2 negative (1+). The patient underwent mastectomy in April 2013. Mastectomy confirmed Nottingham grade 3 invasive ductal carcinoma pT1c/pN0/pMX with peritumoral lymphovascular invasion and invasive tumor less than 1 mm from the superoanterior margin. Due to comorbidities the patient was not considered a candidate for adjuvant chemotherapy. In January 2014 the patient presented with a mastectomy site recurrence. Needle core biopsy confirmed recurrent Nottingham grade 3 ductal carcinoma with papillary differentiation. ER and PR remained negative. However, HER-2 immunohistochemistry showed clear intratumoral heterogeneity. The percentage of total tumor that the positive subclone represented was approximately 1%. The biopsy was vacuum-assisted, generous, and consisted essentially entirely of invasive carcinoma without an in situ component