paraneoplastic features

Small cell

• ADH
• ACTH - not typical, hypertension, hyperglycaemia, hypokalaemia, alkalosis and muscle weakness are more common than buffalo hump etc
• Lambert-Eaton syndrome

Squamous cell

• parathyroid hormone-related protein (PTH-rp) secretion causing hypercalcaemia
• clubbing
• hypertrophic pulmonary osteoarthropathy (HPOA)
• hyperthyroidism due to ectopic TSH

Adenocarcinoma

• gynaecomastia
• hypertrophic pulmonary osteoarthropathy (HPOA)

Hypertrophic pulmonary osteoarthropathy is a proliferative periostisis involving that typically involves the long bones. It is often painful.

*whilst it is traditionally taught that HPOA is most common with squamous cell carcinoma some studies indicate that adenocarcinoma is the most common cause e.g. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4049689/