Fig. 1: Morphologic features of LCIS variants.

The profiled LCIS variants represented relatively discrete lesions on biopsy that displayed a florid growth pattern with massive acinar distention (a), many with central necrosis (b). The LCIS variants met the diagnostic criteria for either florid (c) or pleomorphic (d) LCIS and some displayed apocrine (d) or signet ring cell (e) features. A single case of P-LCIS lacked marked acinar distention, and in retrospect, exhibited borderline nuclear pleomorphism (f). This case was the only one in which an ERBB2 or ERBB3 alteration was not identified.