Skeletal Radiol (2003) 32:530–532 DOI 10.1007/s00256-003-0664-7
Jacques Perrin Wolfgang Zaunbauer Michael Haertel
Received: 1 April 2003 Revised: 13 May 2003 Accepted: 19 May 2003 Published online: 22 July 2003 © ISS 2003
J. Perrin · W. Zaunbauer (✉) · M. Haertel Department of Radiology, Kantonsspital St. Gallen, 9007 St. Gallen, Switzerland e-mail: wolfgang.zaunbauer@ KSSG. ch
C A S E R E P O RT
Brown tumor of the thyroid cartilage: CT findings
Abstract Brown tumor of the larynx is extremely rare. We describe a patient with long-standing primary hyperparathyroidism and severe skeletal involvement associated with brown tumors of the axial and appendicular skeleton and of the thyroid cartilage. Ossification of the laryngeal skeleton may explain the presence of this process in this unusual location.
Introduction Supporting tissue neoplasms of the larynx are rare and account for less than 2% of primary laryngeal neoplasms [1, 2]. Within this group, tumors of the cartilaginous skeleton, including chondroma, chondrosarcoma, amyloidoma, aneurysmal bone cyst, giant cell tumor, aggressive osteoblastoma, osteosarcoma and plasma cell tumors have been amply documented in the literature [1, 2, 3, 4, 5, 6, 7, 8, 9]. The occurrence of a brown tumor in the laryngeal cartilage is extremely unusual. There has been only one previous case report of a brown tumor in the cricoid cartilage [10]. We present a patient with longstanding primary hyperparathyroidism and a brown tumor involving the thyroid cartilage, a unique finding which to the best of our knowledge has not previously been reported.
Case report A 66-year-old white woman presented with intractable multifocal bone and back pain. A history of long-standing weakness, mental alterations, anorexia, hypertension, urinary calculi, nephrocalcinosis, intermittent renal failure, peptic ulcer and pancreatitis in the course of hypercalcemic crisis was also obtained. The patient was a well-documented case of primary hyperparathyroidism, con-
Keywords Primary hyperparathyroidism · Parathyroid adenoma · Brown tumor · Larynx · CT
firmed by biochemical determination at the age of 56 years. But, from fear, she had refused further evaluation and therapy. With regard to the larynx she was asymptomatic. Physical examination of the neck was normal. Laboratory findings of interest included a serum parathyroid hormone level of 2148 ng/l (normal 12–80 ng/l), a serum calcium of 3.1 mmol/l (2.0–2.5 mmol/l), serum phosphorus of 0.6 mmol/l (0.8–1.5 mmol/l) and an alkaline phosphatase of 1,316 U/l (50–330 U/l). Skeletal roentgenograms revealed classic signs of advanced hyperparathyroidism with chondrocalcinosis, soft tissue calcifications, generalized demineralization of bone, subperiosteal, cortical, endosteal and subligamentous bone resorption, and innumerable, well-defined, expanding, radiolucent bone lesions at multiple sites consistent with brown tumors. Computed tomography (CT) of the neck demonstrated a rightsided, retrothyroid, 4.5 cm contrast-enhancing rounded mass of soft tissue density suggesting a parathyroid adenoma (Fig. 1A). CT also showed multiple lytic lesions centrally in the medullary space of the vertebrae, ribs, sternum, scapula, clavicle, humerus and larynx with attenuation values in the range of blood and fibrous tissue (33 HU) and enhancement after intravenous contrast injection (88 HU). The lesions were septated, produced osseous expansion, and were often delimited only by a shell of cortical bone (Fig. 1B). The laryngeal manifestation was 1.7×0.8 cm, central in the medullary space of the ossified left thyroid cartilage ala, well defined, lytic, of heterogeneous attenuation, uncalcified but interspersed with bony trabeculae, expansive, and causing thinning of the overlying intact bony cortex (Fig. 1C). A CT-guided fine needle aspiration biopsy of a prominent rib lesion revealed hemorrhage, proliferating fibrous tissue and multinucleated osteoclast-type giant cells, compatible with a brown tu-
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Fig. 1A–C Brown tumors of the axial and peripheral skeleton and of the thyroid cartilage in a 66-year-old woman with advanced primary hyperparathyroidism. A Axial contrast-enhanced CT scan through the thyroid gland shows a large parathyroid adenoma, retrothyroidal (T, thyroid gland), to the right of the esophagus (E), and medial to the carotid artery (A). B Axial non-contrast CT scan at the level of the tracheal carina shows multiple brown tumors in the sternum and ribs (arrows), with expansive appearance and ballooning of the thinned cortex. On the left the lytic lesion in the rib was proven by biopsy to be a brown tumor. C Axial non-contrast CT scan at the level of the vocal cords (obtained with “bone window” setting) demonstrates a 1.7 cm ovoid geographic radiolucency in the left ossified thyroid lamina (arrows), without airway obstruction. The lesion is well defined, of ground-glass appearance, loculated by bony trabeculae, expanding and thinning the outer cortical bone; there is an associated osseous lesion in the left posterior neural arch of a cervical vertebra (arrowheads)
mor (a biopsy of the thyroid cartilage was not deemed appropriate in the absence of clinical symptoms of the larynx and absence of malignancy). Excision of a 10 g parathyroid adenoma, measuring 4.5×2.3× 1.7 cm, normalized the metabolic values. Five years after surgery, the patient was doing well with improvement in the bone pain but without roentgenographic evidence of healing of the skeletal lesions. Her larynx remained asymptomatic.
Discussion Hyperparathyroidism (HPT) is a pathologic state characterized by the excessive secretion of parathyroid hormone (PTH) and PTH peptides in the serum [12]. HPT may be primary or secondary. In primary hyperparathyroidism (PHPT) PTH production is inappropriate and out of physiologic control. The condition results from parathyroid adenoma, or diffuse hyperplasia, parathyroid carcinoma, and non-parathyroid tumors that secrete a PTHlike substance [12]. Secondary hyperparathyroidism (SHPT) is caused by increased PTH secretion in response to a sustained hypocalcemic state, as a result of chronic renal failure, rarely from malabsorption. In cases of long-standing SHPT the parathyroid glands may appear to function autonomously, a condition known as tertiary hyperparathyroidism. The skeletal changes of HPT have been well described [12, 13, 14]. Brown tumors represent the termi-
nal stage of the bone remodelling processes during PHPT or SHPT [13]. They are non-neoplastic, proliferative disorders of the bone with localized rapid osteoclastic turnover. They are intraosseous soft tissue masses characterized by focal accumulations of active, vascular proliferating fibrous tissue and giant cells in a hemorrhagic stroma [10, 12]. Cysts result from hemorrhage and necrosis within the lesion. They may produce expansion and may progress rapidly. Brown tumors arise in the fibrous tissue overgrowth that replaces bone matrix. They may appear as a solitary lesion or can occur in multiple areas within one bone or as a polyostotic process. These lesions can arise in any bone of the axial or appendicular skeleton, in tubular and flat bones. The most commonly involved sites are the long bones (femur, tibia), digits, pelvis, and facial skeleton. Other radiographic features of HPT are usually present, but occasionally a solitary brown tumor may be the only bone manifestation of HPT. The differential diagnosis for the radiographic appearance of brown tumors includes metastases, multiple myeloma, and fibrous dysplasia. The maturation and aging process of the laryngeal skeleton may allow for an environment in which the development of a brown tumor, attributed to the presence of bone, in previously nonosseous sites may ensue [10]. The cricoid, thyroid, and the greater part of the arytenoids are composed of hyaline cartilage, which begin ossification around 20 years of age. This is an endochondral type of ossification. In older age groups, cartilage consists of variable amounts of nonossified hyaline cartilage, cortical bone, and a marrow cavity containing fat, hemopoietic tissues and scattered bone trabeculae [1, 2, 11]. The epiglottic cartilage consists of elastic cartilage, which, unlike the other cartilage, does not ossify. It is notable that although osseous metaplasia of cartilage is frequent, brown tumor involvement of the laryngeal skeleton is extremely uncommon. There has been only one previous case report of a brown tumor affecting the larynx. Blinder et al. described a single case of a brown tumor in the cricoid cartilage as an unusual manifestation of PHPT in a 84-year-old woman with shortness of breath and hoarseness [10]. CT of the neck demonstrated a well-defined, expansive 24×14 mm lesion destroying the left half of the cricoid cartilage. The mass
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enhanced homogeneously after intravenous contrast injection and caused subglottic narrowing and endoluminal deformity. In our case a brown tumor of the thyroid cartilage was encountered as an incidental finding during a preoperative evaluation of a 66-year-old woman with long-standing PHPT. On the basis of the location and extent of this expansive, uncalcified, lytic, contrast-enhancing lesion with bony trabeculae centered in the medullary space of the thyroid lamina with ballooning of the thinned cortex, the abnormality could be characterized by CT examination. The CT imaging findings were suggestive of a brown tumor and identical to the pathologically proven lesion in the rib. To our knowledge based on a search of
the international literature, there have been no previous reports of a brown tumor in the thyroid cartilage. While endoscopic assessment of submucosal tumors of the laryngeal skeleton is limited, cross-sectional imaging (CT or MR imaging) plays an essential role because it helps detect the lesion, can establish the cartilage of origin, differentiate it from other conditions (e.g., asymmetry of the thyroid cartilage), suggest its benign nature and precisely define the relationships with adjacent structures. Brown tumor presents with certain clinical, pathologic, radiographic and—above all—biochemical features of HPT that clearly distinguish it from a number of other cartilaginous, osteogenic and marrow space lesions of the laryngeal skeleton [2, 3, 4, 5, 6, 7, 8, 9].
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