The purpose of this study was to evaluate 14-gauge stereotactic core needle biopsies (SCNB) obtained by an add-on biopsy device in the diagnosis of mammographically detected non-palpable breast lesions and also to investigate the use of add-on stereotactic device for localizing lesions detected only with galactography. In a study of invasive breast cancers, 14 gauge core biopsies were compared to surgical specimens in the assessment of three clinically important prognostic factors (estrogen receptors (ER), progersterone receptors (PR) and human epidermal growth factor (HER-2)).

Altogether 221 patients with 231 breast lesions were included in the study of SCNBs and 9 patients were included in the wire-localization study. The learning curve was evaluated by comparing the first five biopsies of each of the five radiologists involved in this study with their later biopsies. During the study period between June 1998 and January 2001, core samples were collected in three different containers as follows: the first sample (the central biopsy) was collected into container A, the second and the third samples (obtained 2 mm from the centre of the lesion) into container B, and all additional samples into container C. Histological evaluation and report were performed for each container separately. After core biopsy, all women whose biopsy result indicated the presence of invasive carcinoma or DCIS (ductal carcinoma in situ) underwent surgical treatment. High-risk lesions, such as ADH (atypical ductal hyperplasia) and radial scars were also surgically resected, as were benign lesions with discordant mammographic findings. All other lesions with benign biopsy results were recommended for mammographic follow-up at 1 year and 2 years. The results support the existence of a learning curve in the biopsy of microcalcifications. The sensitivity of 100% for masses and 91% for microcalcifications was reached with multiple samples (more than three). Four false negative cases decreasing the sensitivity in microcalcifications were ADH in three cases and there was one lesion with discordant mammographic and SCNB-findings. Stereotactic 14-gauge core biopsy seems to be at least as sensitive as a surgical specimen in the assessment of ER, PR and HER-2. Three cores are needed for reliable assessment of HER-2 after adding CISH and more than 3 cores for PR, possibly due to tissue heterogeneity. For ER sensitivity remained lower, 95%, even in multiple cores, therefore ER-negative cases should be further investigated from surgical specimens.