Purpose or Case Report: An 18-year-old male initially presented to an outside hospital with acute knee pain after playing sports. MRI of the left knee demonstrated acute complete rupture of the patellar tendon and incomplete rupture of the quadriceps tendon with multiple T1 hypointense, T2 heterogenous well defined osseous lesions in the distal femur, proximal tibia, and fibula. These lesions were concerning for malignancy, so the patient was referred to orthopedic oncology at our institution.
Methods & Materials: At his orthopedic oncology clinic visit 10 days later, the patient was found to have hypercalcemia of 16.2 mg/dL and an acute kidney injury with a creatinine of 2.1 mg/dL and was sent to the emergency department. At that time, a CT chest, abdomen, and pelvis for evaluation of malignancy was ordered and sent to the radiologist to protocol. Upon radiology review of the MRI knee and in combination with the patient’s hypercalcemia, the lesions in the knee were favored to represent brown tumors and radiographs of the knee and ultrasound of the neck for parathyroid adenoma were suggested instead of the CT scans.
Results: Left knee radiograph revealed diffuse osteopenia, cortical erosions, and numerous lytic lesions. Biopsy of the left fibular head lesion confirmed brown tumor. Neck ultrasound demonstrated a left inferior parathyroid mass with increased vascularity measuring up to 3 cm. A Sestamibi SPECT/CT scan confirmed a left inferior parathyroid tumor. Osteolysis of the bilateral clavicular heads and a right T2 vertebral body brown tumor were also noted. Renal ultrasound demonstrated bilateral medullary nephrocalcinosis. Genetic testing was positive for CDC73 gene which is associated with a spectrum of disorders of the parathyroid including parathyroid carcinoma. The patient underwent a left inferior parathyroidectomy with a final pathology of parathyroid carcinoma. Post resection of the parathyroid carcinoma, the calcium level normalized and renal function improved.
Conclusions: Parathyroid carcinoma is extremely rare and should be suspected in a patient presenting with profound hyperparathyroidism, brown tumors, and parathyroid tumor size of ≥ 3 cm. Patients should undergo genetic workup as it is often a hereditary disease.