Expanded lobules filled with enlarged cells which are discohesive.
Some cells have eccentric nuclei, cytoplasmic lumina, and pink cytoplasm. Compared to classic LCIS, the nuclei are enlarged and obviously more pleomorphic, regarded as grade 3.
Focal necrosis (pink material) and even calcifications (purple material) can be found.
Loss of e-cadherin is apparent, consistent with a lobular phenotype.
Lobular carcinoma has several subtypes such as classic (most common), alveolar, tubulolobular, solid and pleomorphic. The pleomorphic variant exhibits more aggressive behavior compared to other subtypes of lobular carcinoma.
Plemorphic LCIS is the in situ counterpart of pleomorphic lobular carcinoma. It is also significant because histologically, it can mimic high grade DCIS. Like high grade DCIS, pleomorphic LCIS exhibits aggressive parameters (e.g. high proliferation index, high grade nuclei, Her2 positivity in a subset).
The distinction of LCIS versus DCIS on core biopsy is important for treatment decisions. Those with DCIS are managed as preinvasive neoplasms with wide local excision, radiation treatment, or mastectomy. The natural history of pure pleomorphic LCIS remains unclear.
Studies have shown an association of pleomorphic LCIS with lobular carcinoma in 25-45% of cases undergoing follow-up resection (Chivukula; Sapino). These findings suggest it may be prudent to follow up core biopies with conservative excision, although this remains a matter of discussion.
Chivukula M, et al. Pleomorphic lobular carcinoma in situ (PLCIS) on breast core needle biopsies: clinical significance and immunoprofile. Am J Surg Pathol. 2008 Nov;32(11):1721-6.
Sapino A, Frigerio A, Peterse JL, et al. Mammographically detected in situ lobular carcinomas of the breast. Virchows Arch. 2000;436:421–430.