Hypercalcemia and local production of parathyroid hormone-related protein by a perisellar rhabdomyosarcoma after remote pituitary irradiation.

OBJECTIVE

To describe a case of metastatic rhabdomyosarcoma originating from the sphenoid sinus in a patient previously treated with conventional irradiation for a prolactinoma, presenting as hypercalcemia in the setting of a normal level of serum parathyroid hormone-related protein (PTHrP).

METHODS

We report the case of a patient who underwent remote pituitary irradiation for a prolactinoma and then presented decades later with hypercalcemia of unknown cause. His clinical course, the initial biochemical and radiologic investigations, and the results of examination of pathology specimens are reviewed.

RESULTS

The patient was found to have a mass in the sphenoid sinus. The pathologic features were consistent with alveolar rhabdomyosarcoma. Although he had a normal serum PTHrP level, staining of his tumor with an antibody against PTHrP revealed local production of PTHrP at the tumor margins. His bone marrow biopsy specimen showed 100% involvement with rhabdomyosarcoma.

CONCLUSION

PTHrP staining of pathology specimens might explain hypercalcemia of undetermined cause in patients with a known malignant lesion, in whom elevated serum PTHrP levels cannot be demonstrated.