Table 1

Differential diagnosis of blunt duct adenosis (BDA) vs columnar cell lesion (CCL) with and without atypia

CCL without atypiaCCL with atypiaBDA
Shape of acini/ducts Round to oval Round to oval Distended, irregular, tubular
ArchitectureFlat, tufts or moundsFlat, tufts or mounds; no well-formed bridges and papillary structuresFlat, tufts or mounds
StratificationPresent in CCL with hyperplasiaMay be presentMild stratification may be present, sometimes (minimal) hyperplasia
Conspicuous cell borders + +
Luminal snouting+++
Intracytoplasmic vacuolesRareRare
Dimorphic cell population (‘pale cells’)RareMore frequent
Myoepithelium Inconspicuous Inconspicuous Conspicuous
Overlapping nuclei Slightly
Nuclear arrangementRegularRegular or disorderlyDisorderly
Nuclear sizeMonotonous, smallMonotonous or variable; enlargedSlightly variable, slightly to moderately enlarged
Nuclear shapeElongated/ovalOval to roundRound to oval, slightly irregular
NucleoliInconspicuous; smallMay be conspicuousSmall to prominent
Position of nucleiBasalUsually centralBasal
Luminal secretion+++
Luminal mucinRareRare
Intralobular stroma Normal Normal Expanded and mildly cellular, often myxoid
Immunohistochemistry CK5 negative CK5 negative CK5 mosaic in hyperplastic areas
Molecular pathology 16q loss 16q loss no 16q loss
  • +/–, may be present; +, usually present; –, not present; CK, cytokeratin.