What is the most probable cause of hypercalcemia in this patient?

A 54-year-old female presents with drowsiness to the emergency. Her BP is 140/90 mm of Hg with pulse after rate 100/minute. Her investigations reveals serum creatinine 2.4 mg/dL, Na 140 mEq/L, K 4.3 mEq/L. Complete blood count (CBC) and liver function test (LFT) is normal. CT scan head is normal. Her past evaluation reveals a cervical lymph node fine needle aspiration cytology (FNAC) suggestive of granulomatous inflammation. Her bone marrow examination is suggestive of non-Hodgkin’s lymphoma.

What is the most probable cause of hypercalcemia in this patient?