What is the broad differential diagnosis for a solitary pulmonary nodule (SPN)?

A solitary pulmonary nodule (SPN) can arise from a wide range of conditions, and option A provides a comprehensive overview of the potential causes. Granulomatous diseases, like sarcoidosis or tuberculosis, are significant contributors to the formation of SPNs, as they can lead to localized inflammation and the development of nodules. Benign hamartomas are also common findings that can present as solitary nodules in the lung, typically characterized by a well-defined, non-cancerous growth.

Other conditions that might contribute to the differential diagnosis of SPNs include lung cancers, which can either be primary tumors originating in the lungs or metastatic cancers from other sites. Additionally, various infections, such as fungal infections, can also form nodular lesions in the lungs.

The other options provided are too narrow in scope and do not encompass the wide variety of conditions that can manifest as an SPN. Limiting the differential diagnosis to lung cancer and pulmonary infections (as in one option) overlooks other significant benign and malignant processes that could present as solitary nodules.