Pleomorphic Lobular Carcinoma In Situ: Radiologic-Pathologic Features and Clinical Management.

Background: Pleomorphic lobular carcinoma in situ (PLCIS) is an unusual variant of LCIS for which optimal management remains unclear.

Methods: We conducted a 15-year (2000-2014) retrospective chart review of the radiologic, pathologic, clinical management, and recurrence rates of patients with PLCIS on diagnostic biopsy. Fifty-one patients were found to have PLCIS either alone or with concomitant breast cancer. Of these, 23 were found to have pure PLCIS on diagnostic biopsy. Rates of upstaging after local excision, positive or close margins, mastectomy, and recurrence associated with pure pleomorphic lobular carcinoma in situ were examined.

Results: Of the 21 patients who underwent surgical excision following diagnostic biopsy, 33.3 % (7/21) were found to have invasive carcinoma, and 19 % (4/23) were found to have ductal carcinoma in situ. Extensive or multifocal PLCIS was present in 47.6 % (10/21) of patients, corresponding to at least one PLCIS-positive or close margin in 71.4 % (15/21). In total, there were 11 local re-excisions in nine patients, and 12 mastectomies. No ipsilateral breast cancer events have occurred, including in those with positive or close surgical margins (mean follow-up 4.1 years).

Conclusions: Patients with isolated PLCIS on diagnostic biopsy are at high risk of upgrading to invasive cancer or ductal carcinoma in situ at diagnostic excision. PLCIS often is extensive, with high rates of positive or close surgical resection margins. If negative PLCIS margins are pursued, rates of successful breast conservation are low. In light of this and low recurrence rates, caution should be exercised in aggressively treating PLCIS with excision to clear margins.