A 53-year-old man develops weakness, malaise, cough with bloody sputum and night sweats. A chest X-ray reveals numerous apical densities bilaterally, some of which are cavitary. Exposure to Mycobacterium tuberculosis was documented 20 years ago, and M. tuberculosis is identified in his sputum. Which of the following describes the expected lung pathology in this patient?

**Core Concept**
The patient's symptoms and history of exposure to Mycobacterium tuberculosis (M. tuberculosis) suggest a diagnosis of tuberculosis (TB) reactivation. The lung pathology associated with TB is characterized by an immune response to the bacterium, leading to the formation of granulomas.

**Why the Correct Answer is Right**
Granulomas are aggregates of immune cells, including macrophages, lymphocytes, and epithelioid cells, that form in response to chronic inflammation and infection. In the context of TB, granulomas are a hallmark of lung pathology, resulting from the body's attempt to contain and eliminate the M. tuberculosis bacteria. The presence of granulomas is a key diagnostic feature of TB, and they can be seen on histopathological examination of lung tissue.

**Why Each Wrong Option is Incorrect**
**Option A:** Dense fibrosis is a feature of chronic lung diseases, such as pulmonary fibrosis, but it is not a characteristic of TB pathology.

**Option B:** Eosinophilic infiltration is typically seen in parasitic infections or allergic reactions, and is not a feature of TB.

**Option D:** Plasma cell infiltration is a feature of chronic infections, such as subacute bacterial endocarditis, but it is not a characteristic of TB pathology.

**Clinical Pearl / High-Yield Fact**
TB granulomas can be classified into several types, including caseating granulomas (also known as necrotizing granulomas), which are characteristic of TB, and non-caseating granulomas, which are seen in other conditions such as sarcoidosis.

**✓ Correct Answer: C. Granulomas**

✓ Correct Answer: C. Granulomas