**Core Concept**
The patient presents with intermittent hemoptysis, a symptom that warrants further investigation due to its association with various pulmonary and cardiac conditions. The presence of malignant cells on sputum cytology, in the absence of radiographic abnormalities, suggests a possible diagnosis of lung cancer with occult metastasis or primary lung cancer with atypical presentation.

**Why the Correct Answer is Right**
In a patient with a history of smoking and hemoptysis, the primary concern is lung cancer. The presence of malignant cells on sputum cytology, despite normal imaging studies, suggests that the cancer may be localized to the bronchial tree or be in an early stage. Therefore, bronchoscopy with biopsy is the next best step to evaluate the extent of disease and plan further management. Bronchoscopy allows for direct visualization of the airways, collection of tissue samples, and assessment of the tumor's location and extent.

**Why Each Wrong Option is Incorrect**
**Option A:**
A CT-guided biopsy may be considered if bronchoscopy is not feasible or if the patient has a contraindication to the procedure. However, in this scenario, bronchoscopy is the preferred initial approach due to its ability to provide direct visualization and tissue sampling.

**Option B:**
A PET scan may be useful in assessing the extent of disease and identifying potential metastases. However, it is not the next best step in management, as it does not provide tissue diagnosis and may not be necessary if bronchoscopy is successful.

**Option C:**
A thoracotomy may be considered in cases of suspected lung cancer with radiographic abnormalities or in patients with a high suspicion of metastatic disease. However, in this scenario, the patient's sputum cytology is positive, and bronchoscopy with biopsy is a less invasive approach that can provide a diagnosis.

**Option D:**
A pulmonary angiogram may be useful in evaluating suspected pulmonary embolism or other vascular abnormalities. However, in this scenario, there are no risk factors for DVT or PE, and the patient's symptoms are more suggestive of lung cancer.

**Clinical Pearl / High-Yield Fact**
In patients with a history of smoking and hemoptysis, lung cancer should be considered in the differential diagnosis, even in the absence of radiographic abnormalities. Bronchoscopy with biopsy is a crucial step in evaluating the extent of disease and planning further management.

**Correct Answer:** C.