Synovial chondrosarcoma of the temporomandibular joint: a case report

Differentiation between Chondrosarcoma and Synovial Chondromatosis of the Temporomandibular Joint Using CT and MR Imaging

BACKGROUND AND PURPOSE

Chondrosarcoma and synovial chondromatosis of the temporomandibular joint share overlapping clinical and histopathologic features. We aimed to identify CT and MR imaging features to differentiate chondrosarcoma from synovial chondromatosis of the temporomandibular joint.

MATERIALS AND METHODS

The CT and MR images of 12 and 35 patients with histopathologically confirmed chondrosarcoma and synovial chondromatosis of the temporomandibular joint, respectively, were retrospectively reviewed. Imaging features including lesion size, center, enhancement, destruction/sclerosis of surrounding bone, infiltration into the tendon of the lateral pterygoid muscle, calcification, periosteal reaction, and osteophyte formation were assessed. A comparison between chondrosarcoma and synovial chondromatosis was performed with a Student t test for quantitative variables and the Fisher exact test or linear-by-linear association test for qualitative variables. Receiver operating characteristic analysis was performed to determine the diagnostic performance for differentiation of chondrosarcoma and synovial chondromatosis based on a composite score obtained by assigning 1 point for each of 9 imaging features.

RESULTS

High-risk imaging features for chondrosarcoma were the following: lesion centered on the mandibular condyle, destruction of the mandibular condyle, no destruction/sclerosis of the articular eminence/glenoid fossa, infiltration into the tendon of the lateral pterygoid muscle, absent or stippled calcification, periosteal reaction, internal enhancement, and size of ≥30.5 mm. The best cutoff value to discriminate chondrosarcoma from synovial chondromatosis was the presence of any 4 of these high-risk imaging features, with an area under the curve of 0.986 and an accuracy of 95.8%.

CONCLUSIONS

CT and MR imaging features can distinguish chondrosarcoma from synovial chondromatosis of the temporomandibular joint with improved diagnostic performance when a subcombination of 9 imaging features is used.

Access to the infratemporal fossa: A modified transzygomatic approach with preservation of masseter attachment and a long-term follow-up period

This study aimed to introduce and evaluate the feasibility of a modified transzygomatic approach with preservation of masseter attachment for the management of infratemporal fossa tumors. This retrospective study included 20 patients treated at Shanghai Ninth People's Hospital, Shanghai Jiao Tong University, between June 2007 and August 2017. Pre- and postoperative radiological findings (magnetic resonance imaging and computed tomography) were obtained from all patients. During an average 67 months of follow-up, no clinical or radiographic signs were found of recurrence or absorption of zygomatic arch defects. The mean visual analog scale score changed from 5.5 preoperatively to 0.6 postoperatively (P<0.001), while the mean maximum inter-incisal opening improved from 21.5 mm preoperatively to 38.7 mm postoperatively (P<0.001). Thus, managing infratemporal lesions using the modified transzygomatic approach may provide functional and esthetically established outcomes.

Nodular Pseudogout of the Skull Base Arising From the Temporomandibular Joint

ABSTRACT

The authors report a case of a rare, large, nodular pseudogout which developed from the temporomandibular joint (TMJ).An 83-year-old female was referred to the hospital with swelling on her left cheek. Imaging studies revealed a large calcified mass surrounding the left mandibular condyle, partially destroying the adjoining bone and extending to the skull base. Magnetic resonance imaging (MRI) revealed soft tissue masses with low signal intensity on T1- and T2-weighted images and were enhanced after intravenous gadolinium injection.The mass was clinically and radiologically suspected to be a neoplastic lesion, such as chondrosarcoma or fibrous dysplasia. However, histological analysis showed that the mass contained granulomatous lesions with numerous multiple nodular rod-shaped and diamond-shaped crystal deposits, which validated the diagnosis of pseudogout. X-ray diffraction (XRD) was performed to identify the tumor's deposited materials and revealed that these were calcium pyrophosphate dihydrate (CPPD) crystals. This result confirmed the histopathological diagnosis of "tophaceous pseudogout."

Calcium pyrophosphate deposition disease of the temporomandibular joint invading the middle cranial fossa: Two case reports

BACKGROUND

Pseudogout is a benign joint lesion caused by the deposition of calcium pyro-phosphate dihydrate crystals, but it is invasive. Pseudogout of the temporo-mandibular joint (TMJ) is uncommon, and it rarely invades the skull base or penetrates into the middle cranial fossa. The disease has no characteristic clinical manifestations and is easily misdiagnosed.

CASE SUMMARY

We present two cases of tophaceous pseudogout of the TMJ invading the middle cranial fossa. A 46-year-old woman with a history of diabetes for more than 10 years was admitted to the hospital due to swelling and pain in the right temporal region. Another patient, a 52-year-old man with a mass in the left TMJ for 6 years, was admitted to the hospital. Maxillofacial imaging showed a calcified mass and severe bone destruction of the skull base in the TMJ area. Both patients underwent excision of the lesion. The lesion was pathologically diagnosed as tophaceous pseudogout. The symptoms in these patients were relieved after surgery.

CONCLUSION

Tophaceous pseudogout should be considered when there is a calcified mass in the TMJ with or without bone destruction. A pathological examination is the gold standard for diagnosing this disease. Surgical treatment is currently the recommended treatment, and the prognosis is good after surgery.

Chondrosarcoma of the Temporomandibular Joint: Systematic Review and Survival Analysis of Cases Reported to Date

The purpose of this systematic review was to summarize the available data on TMJ chondrosarcomas and to perform a survival analysis of cases reported to date. This review was conducted in accordance with the PRISMA. Two authors performed an electronic search of case reports of TMJ chondrosarcoma published until August 02, 2020. Forty-seven studies reporting 53 cases were included. Chondrosarcomas of the TMJ were more prevalent in women, with a male:female ratio of 1:1.4. Survival curves were significantly associated with histological diagnosis (p = 0.004), reconstructive surgery (p = 0.024), recurrence (p < 0.001), and distant metastasis (p = 0.001). Only distant metastasis was independently associated with survival (p = 0.017). TMJ chondrosarcomas presented with low recurrence and higher survival rates than other chondrosarcomas. Synovial subtype, absence of reconstructive surgery, and presence of local recurrence or distant metastasis were associated with poorer prognosis.

Imaging features of chondrosarcoma of the temporomandibular joint: report of nine cases and literature review

AIM

To investigate the imaging features of chondrosarcoma of the temporomandibular joint (TMJ) and review the literature.

MATERIALS AND METHODS

Computed tomography (CT), magnetic resonance imaging (MRI), and integrated positron-emission tomography (PET)/CT images of nine patients with histopathologically confirmed chondrosarcoma of the TMJ were reviewed retrospectively. Imaging features regarding the direction of lesion growth, bone destruction, infiltration into the tendon of the lateral pterygoid muscle (LPM) in the pterygoid fovea, enhancement pattern, calcification, periosteal reaction, markedly hyperintense T2 signal area, and qualitative PET signal intensity were evaluated.

RESULTS

Seven of nine patients (77.8%) presented with lesion growth that was outward from the medulla of the mandibular condyle. Infiltration into the tendon of LPM in the pterygoid fovea was observed in all cases, and 77.8% (7/9) of them demonstrated >50% infiltration. All the lesions showed a mixed peripheral and internal enhancement, and revealed a markedly hyperintense T2 signal intensity area, which showed no enhancement. Although five of nine cases demonstrated higher FDG uptake compared with that of the liver, the other four cases showed less FDG uptake than that of the liver.

CONCLUSION

Chondrosarcoma of the TMJ demonstrated several imaging features, including outward growth from the mandibular condyle, resultant infiltration into the tendon of LPM in the pterygoid fovea, various patterns of internal enhancement, and a markedly hyperintense T2 signal intensity area. These imaging features may be helpful to differentiate chondrosarcoma from other lesions of the TMJ.

Synovial chondrosarcoma: a single-institution experience with molecular investigations and review of the literature

AIMS

To evaluate the available diagnostic histological criteria for synovial chondrosarcoma and to screen for the presence of IDH1/IDH2 mutations in a series of cases of this malignant cartilaginous neoplasm.

METHODS AND RESULTS

Ten cases of synovial chondrosarcoma diagnosed at our institute were reviewed. At presentation, all tumours occurred in adults (median age, 62 years). The most common location was the knee joint (five cases), and the size at diagnosis ranged from 30 mm to 170 mm. Eight patients had secondary synovial chondrosarcomas associated with pre-existing/recurrent or concomitant synovial chondromatosis. Five patients had local recurrences and three had lung metastases. All patients with intralesional excisions developed local recurrences, whereas those who underwent wide resections did not. At last follow-up (mean, 91 months), available for nine patients, seven patients were alive and disease-free, one patient had died of disease, and one was alive with paravertebral metastases. Frequent histological features observed included loss of clustering of chondrocytes (nine cases), the presence of variable amounts of myxoid matrix (eight cases), peripheral hypercellularity (eight cases), tumour necrosis (six cases), and spindling of chondrocytes (four cases). Of the seven cases for which it was possible to evaluate bone permeation, six showed infiltration of bone marrow. All seven cases screened for mutations of exon 4 of IDH1 and IDH2 were found to be wild-type.

CONCLUSIONS

Histological criteria in correlation with clinical and radiological features allow the recognition of synovial chondrosarcoma. IDH1/IDH2 mutations were not present in synovial chondrosarcoma. Adequate surgical margins are important for disease control.

Tophaceous pseudogout of the temporomandibular joint with erosion into the middle cranial fossa

This report presents a case of extensive tophaceous pseudogout involving the temporomandibular joint (TMJ), causing erosion into the middle cranial fossa. Pseudogout is a benign metabolic arthropathy caused by calcium pyrophosphate dihydrate crystal deposition within joints and peri-articular tissue. Pseudogout more frequently occurs in large joints such as the knee, wrist, symphysis pubis, and shoulder. Tophaceous pseudogout involving the TMJ is rare, with only seven cases involving erosion into the middle cranial fossa reported previously. Despite skull base erosion being a rare consequence of this erosive disease, this case highlights the importance of appropriate investigation and multidisciplinary team management.

Benign temporomandibular joint tumours with extension to infratemporal fossa and skull base: condyle preserving approach

This article introduces a modified surgical approach combining condylotomy with posterior disc attachment release for the resection of large non-malignant masses located in the infratemporal fossa and involving the skull base. This retrospective study included 14 patients treated at Shanghai Ninth People's Hospital, Shanghai Jiao Tong University between January 2010 and December 2016. Clinical evaluations (visual analogue scale (VAS) for pain, maximum inter-incisal opening (MIO), and complications) and radiological findings (magnetic resonance imaging (MRI) and computed tomography (CT)) were collected pre- and postoperatively. All patients had satisfactory surgical exposure and complete resection of the neoplasms. During an average follow-up of 54.8 months, no clinical or radiographic signs of recurrence were reported. MIO increased from 28mm preoperatively to 35.4mm postoperatively (P<0.001). The pain VAS score changed from 5.4 preoperatively to 0.7 postoperatively (P<0.001). Neural function was normal for all patients. Postoperative MRI and CT scans showed a satisfactory disc position and condyle morphology, with no resorption. Three-dimensional reconstruction of the postoperative CT scan also demonstrated healing of the skull base defects. The modified surgical approach combining condylotomy with posterior disc attachment release is suitable for the removal of large non-malignant masses involving the infratemporal fossa and skull base.

Soft Tissue Special Issue: Chondroid Neoplasms of the Skull

Clinically, radiologically, and pathologically, chondroid neoplasms of the skull can be diagnostically challenging due to overlapping features in each of these domains. Compounding the problem for the pathologist, there is also significant morphologic, immunophenotypic, and molecular genetic overlap between benign and malignant cartilaginous lesions, and the majority of these lesions are encountered quite rarely in routine surgical pathology practice. Each of these factors contribute to the diagnostic difficulty posed by these lesions, highlighting the importance of radiologic-pathologic correlation in the diagnosis. This review is intended to provide an update for surgical pathologists on some of the most commonly encountered chondroid neoplasms in the skull, and includes the following lesions: chondromyxoid fibroma, synovial chondromatosis, chondrosarcoma and variants, and chordoma and variants. For each of these lesions, the differential diagnosis and useful ancillary tests will be discussed in the context of a broad range of additional primary and secondary lesions.

Chondrosarcoma of the jaw: a retrospective series

OBJECTIVES

Low-grade chondrosarcoma presents with features similar to those of benign lesions, such as chondroma and synovial chondromatosis, increasing the difficulty in reaching an accurate diagnosis preoperatively. In this study, we retrospectively reviewed 10 chondrosarcoma cases and evaluated the diagnostic approaches and management modalities.

STUDY DESIGN

Ten cases were included in the present study. We evaluated the clinical features, initial diagnosis, histopathology subtype, immunohistologic markers, final diagnosis, and treatment modalities.

RESULTS

Most of the lesions were found in the mandible. Two cases were followed up for 1 month and 4 years, respectively as benign lesions before malignant changes were detected. With regard to chondrosarcoma histopathology subtypes, 6 cases were identified as conventional chondrosarcoma, whereas 4 cases were diagnosed as mesenchymal chondrosarcoma with aggressive behavior; of these, 3 were associated with local recurrence and metastasis. The immunohistologic markers showed no specificity for chondrosarcoma.

CONCLUSIONS

Distinguishing low-grade chondrosarcoma, particularly in the temporomandibular joint, from benign lesions, such as chondroma or synovial chondromatosis, remains difficult. Currently, the correlation between clinical, radiographic, and histologic features accompanied by close follow-up is extremely important for patients diagnosed with chondrogenic lesions. Postoperative radiotherapy seems to be beneficial in patients with positive surgical margins.

[Synovial chondromatosis in the temporomandibular joint: analysis of 5 cases]

Five patients with synovial chondromatosis in the temporomandibular joint were treated in our hospital between August, 2011 and August, 2014. All the patients underwent preoperative imaging examinations for clinical diagnosis and determining the involvement of the lesions. Surgeries were performed and the lesions were confirmed as synovial chondromatosis by pathological diagnosis. The clinical manifestations, imaging features, diagnosis and treatment results were analyzed. All the 5 patients had pain in the joint region, 3 had limited mouth opening, and 3 had swelling in the joint region. X-ray film showed widening of the joint space in all the 5 cases and radiographic findings showed space-occupying lesions in the intra-articular space. Open joint surgeries was performed and completed successfully in all the cases. The postoperative imaging showed no residual lesions in the surgical area. As a rare clinical entity, synovial chondromatosis in the temporomandibular joint was poorly documented without specific clinical manifestations. The diagnosis of synovial chondromatosis relies on imaging, arthroscopic and pathological findings. Corpus liberum is an important feature of the disease occurring frequently in the joint cavity. Surgical intervention is the primary choice for treatment of synovial chondromatosis in the temporomandibular joint, in which the corpus liberum and the affected synovial membrane shall be removed after joint incision.

Temporomandibular joint chondrosarcoma: a case report and literature review

Chondrosarcoma is a malignant tumor that originates from cartilaginous cells and is characterized by cartilage formation. Only 5% to 10% of chondrosarcoma occurs in the head and neck area, and it is uncommon in the temporomandibular joint area. This report describes an unusual case with a rare, large chondrosarcoma in a 47-year-old woman who presented with painless swelling and trismus. Computed tomography showed a large mass approximately 8.5×6.0 cm in size arising adjacent to the lateral pterygoid plate and condyle. There were features suggestive of bone resorption. The tumor was resected in a single block with perilesional tissues, and a great auricular nerve graft was performed because of facial nerve sacrifice. Microscopic examination of sections stained with H&E revealed chondrocytes with irregular nuclei and heterogeneous hyper chromatic tumor cells embedded in the chondrocyte lacuna. The diagnosis was a grade I chondrosarcoma. There was no evidence of recurrence at the 8-month follow-up, and a reconstruction surgery with fibular osteocutaneous free flap was performed. We report this unusual entity and a review of the literature.

[Chondromatose of the temporomandibular joint: Multicentric study and clarification from 14 cases]

INTRODUCTION

The aim of our study was to analyse a series of patients suffering from temporomandibular joint (TMJ) chondromatosis treated in 2 departments of stomatology and maxillofacial surgery (University hospitals of the Conception in Marseille and of Caen) and to make a general review of this disease.

MATERIAL AND METHODS

We conducted a retrospective study including all the patients treated for a TMJ chondromatosis in one of these 2 departments. Following parameters were analyzed: sex, ages at discovery and at surgery, symptoms, side, imaging, histology, recurrence and any other events considered as relevant.

RESULTS

Fourteen patients could be included: 85.7 % were women. Average age at diagnosis was 40.14 (σ = 13.82; IC95: 32.90-47.38) (41 for women [σ = 14.74; IC95: 33.28-48.72] and 35 years for men [σ = 5.66, IC95: 27.16-42.84]). Average age at surgery was 40.86 (σ = 14.18; IC95: 33.43-48.28). There was no predominance of side; 57.14 % of the patients had a joint syndrome, 57.14 % a tumor syndrome, 28.57 % had pain and 14.29 % had headaches. Panoramic X-ray was informative in 3 cases only. CT scan showed intra-articular calcifications in half of the cases only but arthrosic modifications in all the cases. Magnetic resonance imaging (MRI) constantly showed intra-articular cartilage fragments. When histology was performed, it found the synovial to be normal in one case and multiple nodules with clear cartilaginous differentiation in another case. One patient suffered from a second contralateral localization 10 years later.

DISCUSSION

Chondromatosis has a slow evolution and is asymptomatic for a long time. MRI allows to evoke the diagnosis and to locate precisely the osteochondromas. Diagnosis is confirmed by histology that highlights a synovial metaplasia and more or less calcified chondromas. The main differential diagnosis to be eliminated because of prognostic reasons is the synovial chondrosarcoma. Treatment consists in surgical removing of the chondromas. Evolution is usually favorable.

Synovial chondrosarcoma

BACKGROUND

Synovial chondrosarcoma (SCH) is a very rare tumor arising in the intra-articular cavity. In the majority of literature reports it is described as a malignant transformation of a pre-existing synovial chondromatosis (SC). We reported a systematic review of primary and secondary SCH described in the literature with the aim to recollect data from different case-reports and case-series, trying to summarize general aspects of this very rare disease.

METHODS

We collected 42 abstracts in the form of case series and case reports, which reported 67 cases of SCH. Studies were taken into account only if they proved a histological diagnosis of SCH, either primary or secondary, with or without evidence of pre-existing SC.

RESULTS

The average age of SCH was 56.9 years, with prevalence for male sex. The average time of malignant transformation was 11.2 years. The most affected joint was the knee (47.7%), followed by hip (34.3%) and ankle (5.9%). SCH was described as de novo sarcoma only in 13 cases (19%). Surgery ended up with amputation in 59.7% of cases. Local recurrence rate was 28.3%.

CONCLUSIONS

We concluded that prognosis of SCH is worse than conventional one and we speculated this is due to the difficult site of the tumor (intraarticular), diagnostic delay and inappropriate previous treatments. We consider that a rapid deterioration of a SC or rapid recurrence after synoviectomy should be considered suspicious of malignant transformation and should be treated in a reference center.

Chondrosarcoma of the temporomandibular joint: a case report and review of the literature

OBJECTIVE

Chondrosarcoma is the second most common sarcoma arising in the bone, but it rarely involves the temporomandibular joint (TMJ). To date, 30 cases of TMJ chondrosarcoma have been reported in the English literature, and the authors report an additional case arising from a cystic lesion in a 60-year-old female patient.

CLINICAL PRESENTATION

The clinical and radiological diagnosis of the lesion was initially synovial cyst, and periodic check-ups were done after aspiration of the lesion. After three years, the patient perceived swelling of the lesion, and surgical excision was performed. The final diagnosis was grade I chondrosarcoma.

CONCLUSION

When clinicians detect a cystic lesion in the radiographic imaging of the TMJ, chondrosarcoma should be included in the differential diagnosis. In addition, computed tomography (CT) as well as magnetic resonance imaging (MRI) is recommended for the accurate diagnosis and proper preoperative planning in TMJ chondrosarcoma.

Synovial Chondromatosis of the Temporomandibular Joint Successfully Treated by Surgery

Synovial chondromatosis (SC) is a chronic process, defined as a reactive cartilaginous proliferation, characterized by formation of cartilaginous nodules, usually loose in the joint space of the synovial membrane. It mainly affects large joints such as knee, hip, shoulder, and elbow, commonly in male patients. However, its manifestation in the Temporomandibular joint (TMJ), is a rare finding, occurring predominantly in females. This paper reports a case of a woman who presented to the service of Stomatology complaining of mouth opening limitations and pain in her left pre-auricular region. After clinical and radiographic analyses, the condition was diagnosed as SC of the TMJ. The loose bodies within the TMJ were removed under general anesthesia. Histological and follow-up features of this lesion are also discussed. To our knowledge, this is the second report of SC of the TMJ in Brazil.

Chondrosarcoma of the temporomandibular disc: behavior over a 28-year observation period

Chondrosarcoma of the head and neck occurs infrequently, with a recorded prevalence of only 5 to 12% of all such tumors; this in total represents only 17 to 22% of all monostotic bone malignancies. Chondrosarcomas arising in the region of the temporomandibular joint are especially rare, with only 28-including subsets-recorded in the 6 decades since the first report in 1954. The lesion described in the present report would appear to be the first arising solely from the disc itself, and the postoperative period of observation is the longest on record. The patient's course over 27 years shows the need for ongoing vigilance in the management of this tumor.

Synovial chondrosarcoma arising in synovial chondromatosis of the temporomandibular joint

Synovial chondromatosis of the temporomandibular joint is rare. Even less commonly documented is the progression of synovial chondromatosis to a synovial chondrosarcoma. The aim of this paper is to present only the third case of synovial chondrosarcoma of the temporomandibular joint. Distinction between these two entities by histology alone is extremely difficult and even though it is advised that the definitive diagnosis should be based on clinical, radiographic and histological evidence, this has proved not to be so simple. The patient, a 63 year old female presented with a swelling associated with her left temporomandibular joint. CT and MRI scans confirmed the presence of a periauricular chondroid mass. Fine needle aspiration biopsy revealed an atypical chondroid lesion that was supicious for a chondrosarcoma. The left temporomandibular joint and surrounding tissues were resected after further imaging and extensive clinical, radiological and cytologic consultations. A diagnosis of synovial chondrosarcoma arising in synovial chondromatosis was made.

Pseudogout of the temporomandibular joint: an uncommon cause of temporomandibular joint pain and swelling

BACKGROUND

Pseudogout, or calcium pyrophosphate deposition, is a rare cause of pain, swelling, and trismus of the temporomandibular joint (TMJ). Diagnosis and management of the lesion are discussed.

CASE DESCRIPTION

A 58-year-old female had a 2-month history of progressive swelling of right TMJ associated with trismus and facial pain. Imaging of the TMJ revealed a mixed radiolucent and radiopaque lesion associated with the right TMJ joint space. Surgical excision was performed successfully via preauricular approach. Pathology was consistent with calcium pyrophosphate deposition of the TMJ, also known as pseudogout. Surgical excision successfully treated her symptoms as expected. She is now disease free without recurrence.

CLINICAL IMPLICATIONS

Pseudogout is a rare cause of TMJ pain, swelling, and trismus that should be included in the differential of joint pain and dysfunction. It can be treated successfully with surgery.

Parosteal chondrosarcoma, a very rare condition of the mandibular condyle

We present a rare case of parosteal chondrosarcoma of the madibular condyle. The patient was referred for a functional limitation of the left temporo-mandibular joint. CT and MRI examinations demonstrated a 3.5-cm cystic mass with a peripheral rim of contrast enhancement located in the left pterygo-maxillary space. The mass had partial intraarticular spread causing deformation and focal cortical erosion of the medial aspect of the condylar head. The lesion was surgically removed; the histological diagnosis was of low-grade chondrosarcoma.

Synovial chondromatosis of the temporomandibular joint: clinical, diagnostic, and histomorphologic findings

Objective. The primary diagnosis of synovial chondromatosis of the temporomandibular joint is extremely rare. Often many months, or even years pass before the diagnosis is confirmed. Study Design. Eight patients with synovial chondromatosis were treated by arthrotomy. In addition to the definitive diagnosis, histologic classification according to the stages proposed by Milgram was undertaken and confirmed with the literature. Results. The predominant symptoms of synovial chondromatosis, including pain, swelling, restricted movement of the mandible, and crepitation, were evaluated. Nevertheless, more than 80% of the patients were previously primarily treated on the basis of other tentative diagnoses. Conclusion. Synovial chondromatosis of the temporomandibular joint should be included in the differential diagnosis of chronic swelling and pain in the preauricular region, and the patient should be sent for appropriate diagnostics and therapy at an early stage.

Differential diagnosis of calcium pyrophosphate dihydrate deposition of the temporomandibular joint

Calcium pyrophosphate dihydrate (CPPD) deposition disease (pseudogout) of the temporomandibular joint (TMJ) is rare. It is characterized by the presence of crystal deposits that are birefringent under polarized light. Although these crystals are characteristically weakly birefringent, some other crystals such as those of calcium oxalate, synthetic steroids, and ethylenediaminetetraacetic acid are also birefringent. The differential diagnosis should therefore be based on a quantitative analysis of crystals or observation of the crystal structure in calcified sections. We present a case of CPPD deposition disease of the TMJ and report on the value of such an analysis to substantiate the diagnosis.