Aims To evaluate the risk of having occult ductal carcinoma in situ or invasive carcinoma in the region of a focus of lobular (in situ) neoplasia (LN) diagnosed on needle core biopsy (NCB) of breast.

Methods All cases of LN diagnosed on NCB of breast over 10 years (2000–2009 inclusive) were reviewed. The clinical presentation, radiological appearances and final pathological diagnosis on open diagnostic biopsy (ODB) were correlated.

Results 125 cases of LN on NCB were identified from diagnostic codes. Of these, 72 (58%) had a coexistent, higher-grade lesion that mandated surgery. Fifty of the remaining 53 (94%) underwent ODB. The majority of patients were asymptomatic, with 68% presenting through the breast screening programme, and in 89% of patients, the target abnormality was microcalcification. Of the 50 patients, 13 (26%) had a final diagnosis of in situ or invasive carcinoma requiring therapeutic surgery. When the cases of pleomorphic LN were excluded, 21% (10/47) were upgraded. Two of these 10 cases had discordant radiology which could have been diagnosed on repeat NCB leaving an upgrade rate of 18% (8/45). In four of the eight cases of invasive malignancy, the disease was multifocal.

Conclusions LN is frequently asymptomatic, being identified by mammographic microcalcification alone. In 21% of classical LN cases, it is associated with an undiagnosed, higher-grade lesion requiring oncological management. In our view, patients with LN discovered on NCB should undergo open diagnostic biopsy.