Brown tumor of the mandible as first manifestation of primary hyperparathyroidism:
diagnosis and treatment
Tumor pardo en la sínfisis mandibular como primera manifestación clínica
de hiperparatiroidismo: diagnóstico y tratamiento

Jacinto Fernández Sanromán ⁽¹⁾, Iosu María Antón Badiola ⁽²⁾, Alberto Costas López ⁽³⁾

(1) Jefe de Servicio. Servicio de Cirugía Oral y Maxilofacial
(2) Jefe de Servicio. Servicio de Anatomía Patológica
(3) Médico Adjunto. Servicio de Cirugía Oral y Maxilofacial. Centro Médico Povisa

Adress:
J. Fernández Sanromán
Servicio de Cirugía Oral y Maxilofacial
Centro Médico Povisa
C/ Salamanca, 5. 36211 VIGO
Tfno: 986 41 31 44.
E-mail: jfsan@telefonica.net

Received: 19-11-2003 Accepted: 8-02-2004

INTRODUCTION

The brown tumor is a localized form of fibrous-cystic osteitis found in the presence of hyperparathyroidism (1,3) (HPT). Histologically, brown tumors are made up by a cell population consisting of mononuclear stromal cells, mixed with multinucleated giant cells, among which recent haemorrhagic infiltrates and hemosiderin deposits (hence the brown colour) are often found (3). Whenever a round, radiolucent, and bone-expanding lesion in the facial bones of a patient with HPT is presented, one have to consider brown tumor as the most likely diagnosis (1). However, when the same type of lesion is found in patients without HPT, a more complex differential diagnosis have to be developed (1-3).

We report a case of brown tumor arising in the anterior mandible of a 16-year-old female as initial clinical symptoms of primary HPT.

CLINICAL CASE REPORT

A 16-year-old woman was referred to the Department of Oral and Maxillofacial Surgery at Povisa Medical Center, Vigo, Spain, in July 1997 with a radiographic finding of a round, radiolucent, and bone-expanding lesion in the anterior part of the mandible. Her past medical history was unremarkable. The patient had began two weeks before with pain over the anterior mandible and drainage of purulent material through the gingival mucosa. On initial examination, an expansive, painful mass in the symphysis region of the mandible was noted. Panoramic radiograph (Figure 1-A) showed a round, radiolucent lesion in the anterior mandibular region with secondary partial resorbtion of the roots of the lower incisors. Data from routine laboratory studies were normal.

With this clinical and radiological findings an odontogenic cyst was suspected. After endodontic treatment of the inferior incisors and canines, the patient underwent extirpation of the lesion and curettage of the bone under general anesthesia. The created bone defect was reconstructed using lyophilized bone covered with a vycril^® mesh (Figure 2). After a 24 hours uneventful postoperative course, the patient was discharged from hospital.

Histologic sections showed a lesion with regions of discrete bone resorbtion with osteoclast activity, some areas with newly formed bone tissue and a loose fibrillar matrix with deposits of hemosiderin. Multinucleated giant cells were also found in the lesion. A giant cell lesion was diagnosed, including brown tumor between the possible causes (Figure 3-A).

The patient was referred to the outpatient clinic of the Department of Endocrinology, at our hospital, to study her parathyroid function. Three weeks after the surgical treatment previously described the patient went to the Urgency Unit suffering from generalized astenia, disruption of the normal walk and generalized muscular pain. Laboratory tests performed on admission gave the following results: alkaline phosphatase, 2124 IU/L; serum calcium, 16.7 mg/dL; Intact parathyroid hormone, more than 1000 pg/mL. Based on these findings, the patient was diagnosed as having hypercalcemia and HPT. Whole-body bone scintigraphy using Tc-99 MDP showed no bone lesions except in the mandible. MRI of the neck demonstrated a nodular mass of 2 cm in the left superior parathyroid gland, which was considered to be a parathyroid adenoma (Figure 4). This tumour was treated by left parathyroidectomy at the Department of Surgery in our hospital. The lesion was histopathologically diagnosed as a parathyroid adenoma. (Figure 3-B).

Postoperative laboratory tests were normal. The panoramic radiograph obtained six years after the initial surgical intervention showed a normal bone consolidation in the anterior part of the mandible (Figure 1-B)

DISCUSSION

Different anatomopathological entities, both benign and malignant, can appear as a lytic lesion in the facial bones (1). In the case of a lytic region of the anterior bony mandible the most likely diagnosis would include: odontogenic cysts and tumours (radicular cyst, lateral periodontal cyst, medial mandibular cyst and ameloblastoma), infectious diseases (bone abscess, localized osteomielitis), metabolic bone diseases (HPT), metastasis from a known or an unknown primary site (lung, breast, kidney, prostate), primary bone tumors and cysts (simple bone cyst, eosinophilic granuloma, giant cell lesions, odontogenic keratocyst, myxoma and odontogenic fibroma).

Giant cell lesions that can arise in the jaw-bones include giant cell tumour, giant cell reparative granuloma, cherubism and brown tumour. Because it is difficult to histologically or radiologically distinguish brown tumor from other giant cell lesions, the clinical diagnosis is made based on the association with HPT (1-3). Histologically, they all have a cell population consisting of rounded mononucleate elements, mixed with a certain number of multinucleated giant cells. In the brown tumour, there is a combination of osteoblastic and osteoclastic activity, often associated with cyst formation, clusters of hemosiderin-laden macrophages, and proliferating fibroblasts.

The brown tumor is mainly due to secondary HPT in patients with renal insufficiency, but it has also been described as a rare manifestation of calcium malabsorption and some forms of osteomalacia (4-6). Nowadays, brown tumor is an extremely rare manifestation of primary HPT. In this case, primary HPT usually results from the overproduction of parathyroid hormone by a parathyroid tumour (7-11) (single adenoma, 2 or more adenomas or carcinoma).

The treatment of HPT is the first step in the management of the brown tumor (in the case of primary HPT the resection of parathyroid adenoma). Brown tumor regression and healing are expected after the correction of HPT. However, several cases of brown tumor that grew even after parathyroidectomy or normalization of HPT level have been reported (12). In these cases brown tumor resection should be the treatment of choice.

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