Primary hyperparathyroidism diagnosed after surgical ablation of a costal mass mistaken for giant-cell bone tumor: a case report

We report the unusual case of a 40-year-old Caucasian woman in which primary hyperparathyroidism was diagnosed after surgical ablation of a costal mass. The mass was suspected of being neoplastic and histopathology was compatible with a giant cell tumor of bone. On the basis of the biochemical results (including serum calcium, phosphorous and intact parathyroid hormone levels) primary hyperparathyroidism was suspected and a brown tumor secondary to refractory hyperparathyroidism was diagnosed.Since giant cell tumor is a bone neoplasm that has major implications for the patient, the standard laboratory tests in patients with bone lesions are important for a correct diagnosis.Primitive hyperparathyroidism (PHPT) is the third most common endocrine disorder after diabetes mellitus and thyroid dysfunction [1]. The estimated incidence of cases of PHPT is 0.2% to 0.3% [2]. The diagnosis of PHPT has classically been based on the demonstration of high plasma calcium and low plasma phosphorus concentrations. In recent years, however, it has been recognized that patients with PHPT may present with plasma calcium concentrations within the normal range [3]. About 75% to 80% of cases of PHPT are diagnosed when a routine assay shows hypercalcemia in patients who are asymptomatic or during evaluation for osteoporosis. Surgical ablation is the treatment of choice for PHPT. Persistent hyperparathyroidism leads to altered osseous metabolism involving bone resorption and tissue changes that are collectively known as osteitis fibrosa cystica (OFC) [3]. Today, < 5% of patients display evidence of OFC [4]. Osteitis fibrosa cystica is characterized by the presence of subperiosteal resorption in the digits, skull and long bones, diffuse osteopenia, and brown tumor [5].Brown tumor is an extremely rare osseous lesion that constitutes a focal manifestation of OFC induced by hyperparathyroidism, independently of its cause. The reported prevalence of brown tumors is 0.1%, and they have been repo