**Core Concept**
Triple negative breast cancer (TNBC) is a subtype of breast cancer characterized by the absence of estrogen receptors, progesterone receptors, and excess HER2 protein. This makes it unique among breast cancer subtypes, as it does not respond to hormone therapy or HER2-targeted therapy.

**Why the Correct Answer is Right**
Triple negative breast cancer tends to be more aggressive and has a poorer prognosis compared to other subtypes. The lack of hormone receptors and HER2 protein means that patients with TNBC rely on chemotherapy and targeted therapies like PARP inhibitors as primary treatment options. The absence of hormone receptors also means that TNBC tends to be more common in younger women and those with a family history of breast cancer.

**Why Each Wrong Option is Incorrect**
**Option A:** TNBC is primarily responsive to hormone therapy. *Wrong because TNBC lacks estrogen and progesterone receptors, making hormone therapy ineffective.*

**Option B:** TNBC is less aggressive than other breast cancer subtypes. *Wrong because TNBC tends to be more aggressive and has a poorer prognosis.*

**Option C:** TNBC is primarily treated with HER2-targeted therapy. *Wrong because TNBC lacks excess HER2 protein, making HER2-targeted therapy ineffective.*

**Clinical Pearl / High-Yield Fact**
TNBC is associated with a higher risk of recurrence and metastasis, particularly to the brain and liver. This highlights the need for aggressive treatment and close follow-up in patients with TNBC.

**Correct Answer:** D.