Table 1.

Morphologic features of different forms of lobular carcinoma in situ

	Classic LCIS (CLCIS)	Pleomorphic LCIS (PLCIS)	Florid LCIS (FLCIS)	LCIS with pleomorphic features (LCIS-PF)
Cytologic features	Dyscohesive proliferation of epithelial cells
	Type A cells (small with uniform hyperchromatic nuclei) OR Type B cells (slightly larger vesicular nuclei with mild variability in size/shape and small nucleoli), OR mixture of Type A and Type B cells	Marked nuclear pleomorphism; >4x size of lymphocyte nucleus (similar to high grade DCIS). May show apocrine features	Similar to classic LCIS: type A or type B, or mixture of both. May show apocrine features	Borderline between classic LCIS composed of type B cells and pleomorphic LCIS
Architectural features	>50% of acini expanded in TDLU	None	a) Little to no intervening stroma between markedly distended acini and/or b) expanded acinus or duct with ~40-50 cells in diameter	>50% of acini expanded in TDLU
Necrosis	Single cell apoptosis or minute foci of necrosis. No comedo necrosis	Comedo necrosis may be present		Single cell apoptosis or minute foci of necrosis. No comedo necrosis
Calcifications	May be present, but usually rare or minute	Coarse calcifications may be present		May be present, but rare or minute