This large, solitary mass in the lung is a primary squamous cell carcinoma (SCC). Both SCC and small cell anaplastic ('oat cell') carcinoma of the lung are strongly correlated with a history of smoking, but the SCC tends to reach a larger size than the oat cell carcinoma, which is more aggressive and metastasizes early. The fine needle aspiration cytology in the second panel demonstrates the typical cytologic features of SCC, with a malignant cell having a very hyperchromatic, angular nucleus and orange cytoplasm. In the third panel, there are islands of neoplastic cells showing keratinization within a collagenous stroma (desmoplasia). The most common paraneoplastic syndrome seen with SCC occurs from elaboration in sufficient amounts of parathormone-related peptide (PTHrP) to produce the syndrome of humoral hypercalcemia of malignancy (HHM).