A 66-year-old man with a 40-pack-per-year history of smoking is investigated for hemoptysis. CXR reveals a central 3-cm mass near the left bronchus. His serum biochemistry is abnormal for elevated calcium, but there is no boney metastasis on the bone scan. Biopsy of the mass is positive for a type of lung cancer associated with paraneoplastic hypercalcemia.For the above patient with lung cancer, select the most likely cell type based on clinical description.

**Core Concept**
The patient's presentation of hemoptysis, a central lung mass, and paraneoplastic hypercalcemia suggests a type of lung cancer that is often associated with these features. This clinical description is characteristic of a specific subtype of non-small cell lung cancer (NSCLC).

**Why the Correct Answer is Right**
The most likely cell type of lung cancer in this patient is squamous cell carcinoma (SCC), which is often associated with paraneoplastic hypercalcemia due to the production of parathyroid hormone-related protein (PTHrP). SCC is a type of NSCLC that originates from the squamous epithelium of the bronchus. The elevated calcium levels in this patient's serum, in the absence of bone metastasis, suggest a paraneoplastic cause, which is a hallmark of SCC.

**Why Each Wrong Option is Incorrect**
**Option A:** Small cell carcinoma (SCLC) is a highly aggressive form of lung cancer that is often associated with paraneoplastic syndromes, but it is less commonly associated with paraneoplastic hypercalcemia compared to SCC. SCLC typically presents with a more aggressive clinical course and is often diagnosed at a later stage.
**Option B:** Adenocarcinoma is the most common type of NSCLC and is often associated with paraneoplastic syndromes, but it is less commonly associated with paraneoplastic hypercalcemia compared to SCC. Adenocarcinoma typically presents with a more indolent clinical course and is often diagnosed at an earlier stage.
**Option C:** Large cell carcinoma is a type of NSCLC that is often diagnosed at an early stage, but it is less commonly associated with paraneoplastic syndromes, including paraneoplastic hypercalcemia. Large cell carcinoma typically presents with a more indolent clinical course.

**Clinical Pearl / High-Yield Fact**
Squamous cell carcinoma of the lung is often associated with a history of smoking and a central location, which makes it more likely to cause paraneoplastic hypercalcemia due to the production of PTHrP. This clinical correlation is a key feature to remember when evaluating patients with lung cancer and hypercalcemia.

**Correct Answer:** C. Squamous cell carcinoma.

✓ Correct Answer: A. squamous cell carcinoma