Lobular Carcinoma In Situ (LCIS)

Epidemiology:

Common sites:

Gross features:

Histologic features:

• Classic LCIS:
• > half of acini of a lobular unit are distended and distorted by a dyshesive proliferation of cells with small, uniform nuclei
• small cells
• non-adherent to eachother
• oval or ound nuclei
• small nucleoli
• signet ring cells containing mucin are common
• intracellular lumens
• underlying architecture of acini is maintained
• mild to moderate nuclear variablity
• pleomorphic LCIS:
• marked nuclear pleomorphism (equivalent to high-grade DCIS)
• comedonecrosis
• eccentric pink cytoplasm

Immunophenotype:

Marker:	Sensitivity:	Specificity:
ER, PR	Almost always (up to 90%) (pleomorphic LCIS is more likely to be neg)
e-cadherin (neg)	80-90% of LCIS and invasive lobular carcinoma
HER2 (neg)	Typically (pleomorphic may be +)
P53 (neg)	Typically (pleomorphic may be positive)
Ki-67	Higher in pleomorphic LCIS

Molecular features:

• same as invasive lobular carcinoma
• 16q loss
• 1q gain
• usually no overexpression of HER2/neu

Other features:

• sdf

References:

• Lakhani SR et al. WHO Classification of Tumours of the Breast (2012)
• Histopathology and immunoprofile sections only