Which histological feature best distinguishes ductal carcinoma in situ (DCIS) from invasive ductal carcinoma (IDC) of the breast?
A. Presence of necrosis within the lesion
B. Absence of an intact myoepithelial layer and invasion through the basement membrane
C. Involvement of multiple ducts
D. High nuclear grade and marked pleomorphism
Explanation
DCIS vs IDC: The Critical Distinction
Key Point
The defining difference between DCIS and IDC is the integrity of the basement membrane and myoepithelial layer. DCIS is confined within the duct; IDC breaches these barriers and invades the surrounding stroma.
Comparative Pathology
Table
Feature
DCIS
IDC
Basement membrane
Intact
Disrupted/absent
Myoepithelial layer
Present (may be attenuated)
Absent
Stromal invasion
No
Yes
Necrosis
May be present (comedo type)
May be present
Nuclear grade
Variable (low to high)
Variable (low to high)
Prognosis
~1–2% risk of progression if untreated
Requires systemic therapy
High-YieldNEET PG
DCIS is a non-invasive lesion confined by the basement membrane. The presence of myoepithelial cells (immunopositive for p63, α-smooth muscle actin) around the lesion confirms DCIS. Loss of this layer = IDC.
Clinical Pearl
DCIS is often detected on mammography as microcalcifications. The grade (low, intermediate, high) and presence of necrosis guide treatment decisions, but the grade alone does not distinguish DCIS from IDC.
