Hypercalcemia Is of Uncertain Significance in Patients With Advanced Adenocarcinoma of the Prostate
Extrarenal production of 1,25(OH)2D by the tumor accounts for about 1% of cases of hypercalcemia in malignancy. 1,25(OH)2D causes increased intestinal absorption of calcium and enhances osteolytic bone resorption, resulting in increased serum calcium. This mechanism is most commonly seen with Hodgkin and non-Hodgkin lymphoma and had been reported in ovarian dysgerminoma.7
In our patient, bone imaging showed osteoblastic lesions, a finding that likely contrasts the local osteolytic bone destruction theory. PTHrP was not significantly elevated in the serum, and PTH levels ruled out any form of primary hyperparathyroidism. In addition, histopathology showed no evidence of mosaicism or neuroendocrine dedifferentiation.
Findings in aggregate tell us that an exact pathophysiologic mechanism leading to hypercalcemia in prostate cancer is still unclear and may involve an interplay between growth factors and possible osteolytic materials, yet it must be studied thoroughly.
Conclusions
Hypercalcemia in pure metastatic adenocarcinoma of prostate is a rare finding and is of uncertain significance. Some studies suggested a search for unusual histopathologies, including neuroendocrine cancer and neuroendocrine dedifferentiation.8,11 However, in adenocarcinoma alone, it has an uncertain pathophysiology that needs to be further studied. Studies needed to investigate the role of PTHrP as a growth factor for both prostate cancer cells and development of hypercalcemia and possibly target-directed monoclonal antibody therapies may need to be extensively researched.
