Carcinoma in situ vs Invasive carcinoma
How to tell Carcinoma in situ and Invasive carcinoma apart when a board question makes them look alike.
In situ stays above intact basement membrane; invasive carcinoma crosses basement membrane into stroma.
Side by side
Carcinoma in situ is full-thickness epithelial dysplasia confined above an intact basement membrane.
Invasive carcinoma breaches the basement membrane and infiltrates stroma, gaining access to lymphovascular spread.
Neoplastic epithelial cells show severe atypia but remain preinvasive until basement membrane invasion occurs.
Basement membrane invasion permits stromal interaction, desmoplasia, and metastatic potential.
Intact basement membrane with full-thickness atypia supports carcinoma in situ.
Stromal invasion, desmoplastic response, or lymphovascular invasion supports invasive carcinoma.
The trap
Severe atypia can look alarming, but invasion status changes staging and metastatic potential.
The repair move
For carcinoma staging, ask whether malignant cells crossed the basement membrane.
Try a free question
CoreA 38-year-old woman has an abnormal Pap smear. Cervical biopsy shows full-thickness atypia of the squamous epithelium with mitoses throughout all layers, but the basement membrane is INTACT. There is no invasion into the underlying stroma. Which diagnosis is most likely?
Show answer and explanation
Answer: A. Carcinoma in situ (CIN III). Carcinoma in situ has full-thickness epithelial atypia with intact basement membrane and no stromal invasion; treatment is excisional procedure (LEEP, cone biopsy) with high cure rate.
Why the other choices are tempting
- B. Invasive carcinoma crosses the basement membrane into stroma.
- C. ASC-US is low-grade cytologic atypia.
- D. Reactive atypia lacks the full-thickness atypia and high mitotic activity.
- E. Microinvasive carcinoma has crossed basement membrane to a limited depth (<3-5 mm depending on site).
Flashcards
Tap a card to flip it.
What membrane is intact in carcinoma in situ?
The basement membrane is intact in carcinoma in situ.
What gives carcinoma metastatic potential?
Invasion through basement membrane gives carcinoma access to stroma and vessels.
Quick answers
What is the fastest way to tell Carcinoma in situ from Invasive carcinoma?
In situ stays above intact basement membrane; invasive carcinoma crosses basement membrane into stroma.
What is the key clue for Carcinoma in situ?
Carcinoma in situ is full-thickness epithelial dysplasia confined above an intact basement membrane.
What is the key clue for Invasive carcinoma?
Invasive carcinoma breaches the basement membrane and infiltrates stroma, gaining access to lymphovascular spread.
What is the common trap with Carcinoma in situ vs Invasive carcinoma?
Severe atypia can look alarming, but invasion status changes staging and metastatic potential.