Which cancer is associated with the use of PTHrP as a paraneoplastic marker?

The association of PTHrP (parathyroid hormone-related peptide) as a paraneoplastic marker is significant in the context of certain malignancies, particularly lung carcinoma and breast cancer.

PTHrP is known to mimic parathyroid hormone (PTH) and can lead to hypercalcemia through its action on bone, resulting in increased bone resorption. Both lung and breast cancers can produce PTHrP, leading to this paraneoplastic syndrome.

In lung carcinoma, especially squamous cell carcinoma, the production of PTHrP is a common mechanism by which these tumors cause hypercalcemia in affected patients. Similarly, breast cancer can also synthesize PTHrP, contributing to hypercalcemia, particularly in cases of advanced disease.

Since both types of cancer have been documented to express PTHrP, this evidence supports the selection of the answer indicating both lung carcinoma and breast cancer as associated with this paraneoplastic marker. Hence, the conclusion that PTHrP is linked to both malignancies is accurate.