Oval, “streaming”, overlapping nuclei separated by irregular distances; nuclei tend to run parallel to the duct wall
Secondary lumens are irregularly shaped (often peripherally located).
“Florid UDH” can be used if ducts are nearly completely filled but don’t meet requirements for ADH or DCIS
No currently agreed upon requirements except that it CANNOT HAVE HIGH GRADE ATYPIA (makes it high grade DCIS if present)
Some pathologists will call ADH if it has all the features of low grade DCIS, but <2mm or <3 ducts or only single duct involved
Monotonous, uniform, round, evenly spaced, low grade nuclei (NO ATYPIA) (no spindled myoepithelial cells within the monotonous central proliferation)
Architectural pattern of DCIS present (Cribriform (circular, sharp, “punched out” lumens); Micropapillary (roman bridges, club shaped, broadened tip); Solid)
Most pathologists like to see >1 focus present and the lesion either measure >2mm or involve >3 ducts to call low grade-DCIS!
If there is pronounced nuclear atypia, it is automatically high grade DCIS regardless of how much is present.
More often associated with necrosis- look for significant nuclear atypia.
Make sure to rule out an invasive component!