Which of the following tumors is specifically linked to hypercalcemia through PTHrP?

Hypercalcemia can occur in various malignancies, often due to the secretion of parathyroid hormone-related peptide (PTHrP), which mimics the action of parathyroid hormone (PTH) and stimulates bone resorption and renal tubular reabsorption of calcium. This leads to elevated calcium levels in the blood.

Squamous cell lung cancer is particularly known for its association with hypercalcemia through the production of PTHrP. This non-metastatic mechanism can lead to a paraneoplastic syndrome presenting with symptoms of hypercalcemia, such as confusion, lethargy, and gastrointestinal disturbances. Recognizing this association is important for managing patients with lung cancer who present with elevated calcium levels.

The other options listed are not typically associated with significant hypercalcemia mediated by PTHrP. Thyroid carcinoma, hepatic carcinoma, and colorectal cancer do not commonly produce PTHrP as a paraneoplastic effect. Instead, other mechanisms may lead to hypercalcemia in some malignancies, but PTHrP is most characteristically linked to squamous cell lung carcinoma.