Ossification of the cervical ligamentum flavum and osseous brown tumor: late manifestations of primary hyperparathyroidism misdiagnosed in a case of parathyroid carcinoma.

Parathyroid carcinoma represents an extremely rare neoplasm with diverse clinical manifestations. Herein we aimed at presenting an unique case of a young patient with late manifestations of parathyroid cancer and reviewing the relevant literature. A 45-year-old male patient presented in the Outpatient Clinic with an episode of nephrolithiasis. His personal medical history includes: recurrent episodes of nephrolithiasis, laminectomy in the cervical spine due to ossification of the cervical ligamentum flavum and surgical resection of a giant cell tumor of the brain. Laboratory testing revealed findings of primary hyperparathyroidism (serum calcium 16,0 mmol/l phosphorus 1,46 mg/dl and parathyroid hormone/PTH 8560 pg/ml). Neck ultrasound and technetium-99 m sestamibi scan were performed showing a parathyroid tumor. Due to the persistently high serum calcium and PTH levels, the high alkaline phosphatase levels (440 IU/L) and the late manifestations of HPT, surgical excision of the tumor was performed. The tumor was identified as parathyroid carcinoma. Immediately after surgery serum calcium and phosphorus levels were normalized. The patient is on a regular follow-up program with no signs of recurrence or metastasis one year after the excision. We describe the coexistence of rare late manifestations of HPT, which had not been adequately investigated at their onset in this young patient. Therefore, increased awareness is needed in order to recognize and further investigate signs or symptoms of HPT.