Fig. 1: Representative images of LCIS variants sequenced in this study.

a, b Pleomorphic LCIS (a) (case P6) showed marked nuclear pleomorphism, equivalent to that of high-grade DCIS, and associated invasive lobular carcinoma (b) typically showed pleomorphic cytology and growth pattern. c, d This pure pleomorphic LCIS (pP2) had apocrine cytology, characterized by large cells with abundant eosinophilic granular cytoplasm (c). The neoplastic cells lack estrogen receptor expression (d). e, f Florid LCIS (case F1) had similar cytology to classic LCIS but showed marked expansion of terminal duct lobular units or ducts, with little to no intervening stroma between expanded lobules (e). The associated invasive lobular carcinoma in this case showed classic cytology and growth pattern (f).