All of the following are invasive carcinoma of breast except -a) Comedo carcinomab) Colloid carcinomac) Lobular carcinoma in situd) Medullary carcinoma

**Core Concept**
The question is testing the classification of invasive and non-invasive breast carcinomas. Invasive carcinomas are characterized by their ability to penetrate the basement membrane and invade surrounding tissues, whereas non-invasive carcinomas remain confined to the ductal or lobular epithelium.

**Why the Correct Answer is Right**
Lobular carcinoma in situ (LCIS) is a non-invasive precursor lesion that represents an increased risk of developing invasive breast cancer, but it does not invade the basement membrane. In contrast, the other options are all invasive carcinomas of the breast. Comedo carcinoma is a subtype of ductal carcinoma in situ (DCIS) that is characterized by its comedonecrosis, but it is still considered non-invasive. However, the other options listed are all invasive carcinomas. Colloid carcinoma is a subtype of invasive lobular carcinoma that is characterized by its mucinous stroma. Medullary carcinoma is an invasive carcinoma that is characterized by its syncytial growth pattern and prominent lymphocytic infiltrate.

**Why Each Wrong Option is Incorrect**
**Option A:** Comedo carcinoma is a subtype of non-invasive ductal carcinoma in situ (DCIS) that is characterized by its comedonecrosis, but it is still considered non-invasive.

**Option B:** Colloid carcinoma is an invasive carcinoma, characterized by its mucinous stroma and invasive growth pattern.

**Option C:** Lobular carcinoma in situ (LCIS) is a non-invasive precursor lesion that represents an increased risk of developing invasive breast cancer, but it does not invade the basement membrane.

**Option D:** Medullary carcinoma is an invasive carcinoma that is characterized by its syncytial growth pattern and prominent lymphocytic infiltrate.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the classification of breast carcinomas is based on their ability to invade the basement membrane and surrounding tissues, and that non-invasive precursor lesions like LCIS represent an increased risk of developing invasive breast cancer.

**Correct Answer:** C. Lobular carcinoma in situ.