The Relationships between HER2 Overexpression and DCIS Characteristics.

The aim of this study was to demonstrate the correlation between human epidermal growth factor receptor 2 (HER2) overexpression and some poor prognosis factors in patients affected by ductal carcinoma in situ (DCIS). We evaluated 48 cases of DCIS, divided into two groups according to HER2 amplification status. Nuclear grade and "cancerization of lobules" were determined within primary DCIS and Ki67, estrogen receptor (ER), PR, and HER2 expression was established using immunohistochemistry. The histopathological variables in HER2-positive and in HER2-negative patients were compared to determine the recurrence risk. We also considered the median age at the time of surgery according to HER2 status. There were 11 recurrences (23%), 6 DCIS (55%), and 5 invasive cancer (45%). In an 8-year-long median follow-up, we hypothesized high risk of recurrence in HER2-positive DCIS. Patients with HER2-positive DCIS were younger than HER2-negative ones (p = 0.002). HER2-positive DCIS was also related to histopathological predictors of recurrence such as high nuclear grade (p < 0.001), high Ki67 expression (p = 0.003), low ER and PgR levels (p < 0.001), and the presence of "cancerization of lobules" (p < 0.049). Our trial suggests that HER2 amplification in primary DCIS is identified more frequently in younger patients and hypothesizes high risk of recurrence in HER2-positive DCIS related to histopathological predictors of overall relapse as high nuclear grade, high Ki67 expression, low ER and PgR levels, and the presence of "cancerization of lobules." In HER2-positive DCIS, other variables of recurrence risk are compared to HER2-negative lesions, without statistical significance. Our results show that HER2 testing might suggest clinicians the optimal treatment of patients with DCIS.