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Sample Question Breast

The following breast lesion was found on skin biopsy. Deeper biopsies performed for calcifications showed ductal carcinoma in situ (DCIS). Which is true regarding the pictured lesion?

The lesion is in situ.

✓ Correct Answer

Correct. Paget's disease of the nipple is considered to be an situ lesion. The prognosis is dependent on the characteristics of the underlying lesion.

Tumor cells are triple negative (ER, PR, Her2 negative).

Incorrect. Tumor cells of Paget's disease of the nipple are positive for low molecular weight cytokeratins (Cam 5.2, CK AE1/AE3), CK7, Her2, and androgen receptor. They are variably positive for ER and PR, but are usually negative, the same as the underlying tumor.

The tumor is upstaged to pT4 because of skin involvement.

Incorrect. Paget's disease is not considered skin invasion for the purposes of staging. DCIS in conjunction with Paget's is staged as “pTis (Paget)".

Tumor cells are negative for CK 7 and positive for melan A.

Incorrect. The history and morphology are more consistent with Paget's disease of the nipple than melanoma. Paget's disease is positive for CK7 and Her2, and more frequently negative for ER and PR.

The lesion is present in 15% of patients with breast carcinomas.

Incorrect. The lesion is present in 1-2% of patients with breast carcinoma.

Summary: Paget's disease of the nipple is an IN SITU lesion that occurs in ~2% of patient with breast carcinoma. By IHC it is positive for CK7 and Her2, and usually negative for ER and PR, the same as the underlying carcinoma.

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