Feature | CCC | CCH | FEA | ADH |
Cell morphology | Columnar | Columnar | Columnar and/or cuboidal | Cuboidal |
Number of cell layers | ⩽2 | >2 | Variable | Variable |
Architecture | Flat | Tufts/mounds | Flat or tufts/mounds. Not complex∗ | Complex architectural pattern∗ |
Nuclear atypia† | Absent | Absent | Present | Present |
Nuclear features† | Ovoid, bland, polarised nuclei arranged perpendicular to basement membrane | Ovoid, bland; some nuclear crowding and overlapping of nuclei may be observed. Nuclei arranged perpendicular to basement membrane | In typical form: round, uniform, evenly-spaced with finely dispersed chromatin, as in low grade DCIS. Alternatively may show more “classical” cytonuclear atypia in the form of enlarged, more oval nuclei with mild to moderate pleomorphism; some clumping of chromatin may be seen | Round and evenly spaced as in low grade DCIS; finely dispersed chromatin |
Nuclear to cytoplasmic ratio | Normal | Normal | Increased | Increased |
Internal contours of acini | Irregular | Irregular | Typically smooth | Variable |
ADH, atypical ductal hyperplasia; CCC, columnar cell change; CCH, columnar cell hyperplasia; FEA, flat epithelial atypia; DCIS, ductal carcinoma in situ.
∗True micropapillae (with bulbous tip extending into the lumen from a narrower stalk) or sieve-like cribriform spaces.
†Cases with high grade nuclear atypia should be classified as flat high grade DCIS and do not fall within either the spectrum of FEA or of ADH.