Screen‐detected pleomorphic lobular carcinoma in situ (PLCIS): risk of concurrent invasive malignancy following a core biopsy diagnosis

Abstract

Pleomorphic lobular carcinoma in situ (PLCIS) is an uncommon, recently recognized variant of lobular carcinoma in situ (LCIS). Its natural history, biological behaviour and clinical characteristics are uncertain. The aim was to review the radiological and pathological findings in a series of screen-detected PLCIS diagnosed on needle core biopsy with a view to determining the diagnostic features, immunohistological profile and risk of concurrent invasive malignancy. Ten cases of core biopsy-diagnosed, screen-detected PLCIS were identified. Core biopsy findings were compared with pathological findings at subsequent surgery. Two cases were associated with possible microinvasion on the core. Two of 10 had invasive lobular carcinoma and one had microinvasive lobular carcinoma on subsequent surgical excision (positive predictive value for malignancy = 30%). There was associated conventional LCIS on either core or excision biopsy in all cases except one. All three cases of oestrogen receptor (ER)-negative PLCIS arose in the context of ER+ conventional LCIS. PLCIS is a potentially more aggressive lesion than conventional LCIS and may present as mammographic calcification through a breast screening programme. Diagnosis may be problematic and immunohistochemical markers including ER may prove a useful diagnostic adjunct. There is a significant risk of concurrent invasive carcinoma following a core biopsy diagnosis.