**Core Concept**
Heart failure cells, also known as siderophages, are macrophages that accumulate in the lungs due to the breakdown of red blood cells, leading to pulmonary congestion in patients with heart failure. This phenomenon is a result of the increased pressure and fluid overload in the lungs, causing damage to the alveolar-capillary membrane and subsequent leakage of red blood cells into the alveolar space.

**Why the Correct Answer is Right**
Heart failure cells are characterized by the presence of hemosiderin, a breakdown product of hemoglobin, within the macrophages. This occurs due to the ingestion of red blood cells that have leaked into the alveolar space. The macrophages, now known as siderophages, contain hemosiderin granules, which are visible under the microscope. This accumulation of hemosiderin-laden macrophages is a hallmark of heart failure cells.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the cellular component of heart failure cells.
*Option B:* This option is incorrect because it is not the primary cellular component of heart failure cells.
**Option C:** This option is incorrect because it is not a characteristic feature of heart failure cells.

**Clinical Pearl / High-Yield Fact**
In patients with heart failure, the presence of heart failure cells in the lung biopsy is a strong indicator of pulmonary congestion and fluid overload.

**Correct Answer:** C.