Stereotactic incisional core breast biopsy (SCBB) is a highly specific technique for diagnosing ductal carcinoma in situ (DCIS) in patients with suspicious mammographic microcalcifications. However, its sensitivity for excluding the presence of coexisting occult invasive disease in this setting is not fully established.
We correlated SCBB findings to subsequent lumpectomy/mastectomy (lx/mx) results in 122 cases of DCIS. In 29 of these cases, the SCBB showed microscopic invasion (n = 15) or foci that were suspicious for invasion (n = 14). Likelihood for invasive disease in subsequent lx/mx samples from each case then was compared with various parameters, including DCIS grade, extent and mammographic findings.
Overall, 13% of cases in which the SCBB showed DCIS only (i.e., without any evidence of invasion), had invasive disease in the subsequent excision. This finding was significantly correlated with DCIS grade (low: 0/26 [0%], intermediate: 2/31 [6%], high: 10/36 [28%], P <.001). Invasive lesions were usually small (nine T1a, one T1b, and two T1c) and typically present within more extensive fields of DCIS (no invasion: 1.5 cm DCIS size; invasion: 2.8 cm mean DCIS size, P =.01). This was reflected by greater extent of involvement in the SCBB (5/8 cases with invasion had >15 ducts involved, versus 4/23 with <15 ducts involved, P =.03). SCBB that were suspicious or positive for microinvasion demonstrated invasion in most subsequent excision (susp: 7/14 [50%], microinv: 11/15 [73%]), generally of significant extent (11/18 T(1b-c)).
1. Patients with SCBB showing high grade DCIS and DCIS suspicious or positive for microinvasion have a significant and high likelihood, respectively, of harboring occult invasive neoplasm. They should accordingly be carefully evaluated radiographically, and possibly with sentinel node biopsy to facilitate axillary staging. 2. Likelihood of occult invasion is correlated with overall DCIS size/extent.