FormalPara Key Points

  • Growing masses, benign and malignant, can alter TMJ functions and mimic symptoms that are also encountered in the most common temporomandibular disorders.

  • TMJ tumors are uncommon. They can be primary tumors, secondary tumors, and metastases.

  • Masses detected on CBCT and TMJ MRI will need further assessment. In the case of malignancies CT and MRI have to be extended within the head and neck. Contrast is mandatory for malignant tumors and imaging modalities are performed differently, with the purpose of locoregional staging and surgical planning.

  • Benign tumors have a slow growth, nonspecific symptoms and may undergo a significant delay in diagnosis because of misinterpretation or overlooking.

  • Malignant tumors generally show a rather rapidly grow mass, perhaps involving surrounding anatomical regions (ears, parotid, medial cranial fossa, infratemporal fossa, zygomatic and temporal bone).

  • Primary malignancies from breast, lung, prostate, kidney, rectum, and stomach may spread to this region. TMJ metatases are extremely rare.

  • Management depends on patient age, tumor extension, and behavior, ranging from simple curettage to resection with total TMJ reconstruction. Final diagnosis is histological after surgical intervention.

  • Prognosis of benign tumors is very good, on the other hand, malignant tumors have poor survival rates.

  • Tumor-like lesions are condylar or intra-articular non-neoplastic enlargements which behave like space-occupying masses.

The purpose of this chapter is to provide knowledge about tumors that affect temporomandibular joint (TMJ) function. Because of this, details on tumor biology, behavior, and treatment will not be discussed. Tumors and pseudotumors can mimic more common non-neoplastic conditions given that pain and impairment are common features. Focus will therefore be on these aspects and on imaging of the most prevalent, although rare, TMJ tumors.

TMJ tumors can be primary, secondary (spreading from adjacent structures) or they can be metastases from a distant primary malignant tumor. Primary tumors, benign and malignant, can originate from bone, cartilage , or soft tissue and progressively enlarge, thus occupying the joint space to various degrees. Tumor masses commonly remain silent until their size increases and symptoms appear, and they can be incidentally detected when imaging is carried out for other reasons (Mostafapour and Futran 2000; Al-Jamali et al. 2013).

9.1 Benign Tumors

9.1.1 Imaging of Benign Tumors

Presence of benign tumors and pseudotumors is often an incidental finding on orthopantomogram, CBCT, or MRI. In such cases the patient will be referred for further evaluation, biopsy procedures, and treatment planning.

Imaging signs for osteolytic and osteoblastic lesions hold true for bone lesions in general and for the jaws (Harmon et al. 2015). Aggressiveness can be inferred from radiological assessment. For instance, a sclerotic, well-defined lesions with no periosteal reaction (like in the case of osteoma ) will not show an aggressive behavior which is instead to be expected if new bone tissue with an osteoid matrix and triangular spicule-like periosteal reaction is found, like in the case of osteosarcoma .

Radiological features need to be associated with patient age and location so that differential diagnosis can be processed down to a few, perhaps more frequent, histotypes (Kaplan et al. 1994). Small intra-articular loose calcified bodies may therefore reveal pigmented villonodular synovitis (PVNS) , pseudogout, or rice-body rheumatoid arthritis (Romañach et al. 2011).

Non-aggressive benign lesions will require CT scan which may be carried out as CBCT, as long as the Field of View is sufficient. MRI may further be required to have an overview on soft tissues and joint function whenever the expanding mass is thought to have an effect on joint mechanics. In such an instance, MRI might as well be of the TMJ only, with no intravenous contrast (Boeddinghaus and Whyte 2008).

The most significant features of benign tumors are outlined below however, as a general rule, osteochondroma and osteoma show regular cancellous bone or compact bone (osteosclerosis), whereas ossifying fibroma, chondroblastoma, and osteoblastoma have radiotransparent areas (osteolysis) within which osteosclerosis can also be found.

9.1.2 Osteochondroma

Osteochondroma (OC) is a benign, slowly growing tumor also known as osteocartilaginous exostosis (Koga et al. 2006). It presents like an exophytic mass with a broad base, usually extending anteromedially in the direction of the upper belly of the lateral pterygoid muscle . It causes condylar enlargement and deformity (Fig. 9.1a–e). Cortical bone is usually macroscopically irregular but preserved, and cancellous bone may show some trabecular thinning. As a rule, a cartilaginous cap is covering this bony outgrowth and this helps in the differential diagnosis with osteoma (Unni 2010; Sekhar and Loganathan 2015; Mehra et al. 2016). Other conditions may be confused with this benign tumor: smaller osteochondromas may at times resemble an osteophyte (Fig. 9.2a–c) or a healed condylar fracture. Non-ossifying fibroma, much like other expanding fibrous bone lesions, can also cause condylar enlargement, however it differs from osteochondroma in that it displays newly formed bone with partial ossification.

Fig. 9.1
figure 1figure 1

Voluminous osteochondroma (white arrow) of the left mandibular condyle, which has caused deformity and an increase in size of the condyle with respect to the contralateral in sagittal SE PD (a), axial SE T1 (b), and coronal SE T2 (c) images. Condylar deformity is more prominent at the medial pole as seen on the coronal plane both in MR (c) and in CBCT (d). The pars intermedia shows a wide perforation causing the disc to be ring-shaped. The disc surrounds the condyle (black arrows), and movement is preserved, as demonstrated by the open-mouth sequence (e). The articular surfaces of condyle and glenoid cavity are irregular. The fossa appears reshaped and it shows slight subchondral sclerosis

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Fig. 9.2
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Small osteochondroma (white arrows) of the medial pole of the left condyle. The lesion develops anterocranially (sagittal SE PD a–axial SE T1 b) along the superior head of the lateral pterygoid muscle . In a SE T2 coronal sequence (c) the small osteochondroma is similar in appearance to an osteophyte of the medial pole

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9.1.3 Osteoma

TMJ osteoma is a rare, benign, slowly growing tumor composed of either cortical or cancellous bone (Almeida and de Oliveira Filho 2011; de Souza et al. 2017). It can arise as a single mass, and as such it is less frequent than osteochondroma, or more rarely, it is part of Gardner syndrome (familial adenomatous polyposis), as patients affected may present multiple craniofacial osteomas.

It presents as a well-defined mass made of compact bone, with round margins originating from the condylar surface. It is easily distinguishable from osteochondroma because of its sclerotic, well-defined, and radiopaque appearance (Bessho et al. 1987; Nah 2011).

9.1.4 Ossifying Fibroma

Ossifying Fibroma (OF) is defined as a benign tumor, with defined margins, made up of a fibrous tissue and variably calcified areas (Barnes et al. 2005; Zavattero et al. 2013). Within the head and neck, this tumor is mostly found in the molar region of the mandibular body as differentiation of bone and cementum has an odontogenic significance here and in tooth-bearing areas. Cementum-like elements may actually be present among the mineralized component of OF and this led in the past to the name cemento-ossifying fibroma. OFs are diagnosed between the second and the fourth decade of life, with a female predominance. In the TMJ, OF is rare, slow-growing, and composed of bone at different maturation stages together with a fibrous component (Brannon and Fowler 2001). The growth pattern has a tendency to cortical expansion as well as a local aggressiveness.

Differential diagnosis includes fibro-osseous conditions such as fibrous dysplasia.

9.1.5 Chondroblastoma

Chondroblastoma with TMJ involvement has been described, but it represents an extremely rare occurrence. Origin from within the TMJ is even more rare (Bui et al. 2009).

This tumor has a cartilaginous origin, it contains multinucleated giant cells, and it presents as an oval radiotransparent mass with thin defined margins (Toro et al. 2005). Its behavior is nonaggressive, however, it may recur after resection. More aggressive behavior with bone resorption has also been reported in the literature (Kim et al. 2015).

Extracranial localizations of this tumor are known to be particularly painful and occurring at a young age, whereas the few reports of TMJ chondroblastoma usually indicate painless, older patients (Toro et al. 2005).

9.2 Malignant Tumors

Signs and symptoms of TMJ malignant tumors show a rapid onset swelling and pain in the preauricular area combined with lower jaw hypomobility, trismus, and changes in occlusion. Facial asymmetry is a common sign, however other features, such as neurological motor or sensory impairment, may arise as well and they indicate involvement of adjacent structures.

9.2.1 Imaging of Malignant Tumors

When CBCT or TMJ MRI reveal aggressive bone lesions, further contrast CT or contrast MRI must be carried out according to head and neck tumors protocols (Juliano and Moonis 2018). Imaging techniques must be able to deliver necessary information regarding biopsy procedures, staging, and surgical resection (Boeddinghaus and Whyte 2008).

9.2.2 Chondrosarcoma

Chondrosarcoma (CHS) is a rare malignant mesenchymal tumor derived from cartilage cells. Head and neck chondrosarcomas represent up to 12% of all chondrosarcomas (Oh et al. 2016).

The tumor mass is generally slow-growing, it can cause condylar erosion and affect adjacent structures because of tumor growth.

CHS may be classified as either primitive or secondary, depending on whether it develops from otherwise healthy bone or from pre-existing lesions (enchondroma, osteochondroma) (Garzino-Demo et al. 2010; Giorgione et al. 2015; Macintosh et al. 2015).

Depending on type (endosseous or peripheral CHS) and grading, CT and MRI appearance may vary sensibly. Grade I CHS will show areas of cartilage matrix with calcifications, from Grade II to Grade III such areas extend and their signal characteristics get more and more different from those of cartilage. Contrast-enhancement in grade I CHS is peripheral and ring-and-arc-like, whereas it spreads out and intensifies in higher, more aggressive grades.

Concerning TMJ MRI, it is important to distinguish cartilage of synovial chondromatosis, for instance, from newly formed cartilage of a grade I CHS. Synovial chondromatosis occupies the joint space and may cause joint surface erosion. Differential diagnosis of CHS is therefore essentially made with synovial chondromatosis, chondroblastic sarcoma, osteogenic sarcoma, and metastases (Angiero et al. 2007; Oliveira et al. 2009; Macintosh et al. 2015).

9.2.3 Osteosarcoma

Osteosarcoma is a highly malignant tumor which most commonly affects the long bones (Bennett et al. 2000; dos Santos and Cavalcanti 2002). Only 5–6% of all osteosarcomas arise in the jaws, making TMJ osteosarcoma an extremely rare occurrence (Schwartz and Alpert 1963; Mardinger et al. 2001; Zorzan et al. 2001). It is a mesenchymal stem cell tumor and it produces immature bone. Predisposing factors associated with the tumor are: pre-existing lesions (bone cysts), fibrous dysplasia, previous radiation therapy, osteogenesis imperfecta, genetic factors, and viral agents (August et al. 1997; Van Es et al. 1997; Mardinger et al. 2001; Zorzan et al. 2001; dos Santos and Cavalcanti 2002).

The mass grows rather rapidly and it easily involves the surrounding anatomical regions (ears, salivary glands, medial cranial fossa, infratemporal fossa, zygomatic and temporal bone). TMJ osteosarcomas tend to metastasize later compared to those of other bones (Wang et al. 2012).

Differential diagnosis includes metastatic disease, chondrosarcoma , aneurysmal bone cyst .

Imaging features in both CT and MRI depend upon histotype. Osteosarcoma has been differentiated into chondroblastic, fibroblastic, osteoblastic, and telangiectatic osteosarcoma. Rare telangiectatic forms will show a purely lytic lesion with fluid levels, while osteoblastic osteosarcoma exhibits an osteoblastic ivory area with intense calcified spicule-like periosteal reaction.

9.2.4 Metastasis

Metastatic disease of the TMJ often presents with nonspecific symptoms. There may be pain, swelling, pathological fracture, some degree of TMJ dysfunction, occlusal changes, hearing loss, facial asymmetry, trismus, and trigeminal paresthesia (Kruse et al. 2010). Hematogenous dissemination of tumors to this area is indeed very rare. In most cases there is a well-known medical history of tumor, however in a limited number of cases, joint disease will lead to the discovery of an unknown primary disease (Qiu et al. 2013; Guarda-Nardini et al. 2017).

Most common primary malignancies metastasizing to TMJ include breast, lung, prostate, kidneys, rectum, and stomach (Smolka et al. 2004; Miles et al. 2006; Katsnelson et al. 2010; Freudlsperger et al. 2012). Rareness may be explained by a relatively poor quantity of hematopoietic marrow as opposed to other parts of the jaws (such as the mandibular molar area) which are instead more commonly affected by metastatic tumors (Porter et al. 1996; Kruse et al. 2010; Matsuda et al. 2017).

9.3 Tumor-Like Lesions

Tumor-like lesions of the TMJ can potentially occupy the joint space because of their expansive behavior (Clayman 2006). Due to their prognosis as well as signs and symptoms, they can be compared to benign tumors .

9.3.1 Imaging of Tumor-Like Lesions

Cystic lesions of the condyle appear radiotransparent in orthopantomograms and hypodense in CT. Because of their nature, they will appear hyperintense in T2 and STIR MRI sequences, and hypointense in T1. In general, tumor-like lesions follow the same imaging principles of benign tumors and differential diagnosis will often take these into consideration. Cystic lesions are also to be distinguished from subchondral bone cysts that instead belong to degenerative joint disease or rheumatological conditions. True cystic lesions most probably have distinct bone walls that can better be described by CT scan rather than MRI. Among these, aneurysmal bone cyst expands like a cystic void whose cortex remarkably thins out as growth continues centrifugally, leading to a discontinuous aspect of the cortical bone itself. Fluid levels can be detected in MRI.

9.3.2 Synovial Chondromatosis

Synovial chondromatosis (SC) is a rare, benign and chronic cartilaginous metaplasia of the mesenchymal remnants of the synovial tissue. Cartilaginous nodules are formed and they are either pedunculated or detached from the synovial membrane, thus becoming loose bodies within the joint space (Milgram 1977). SC usually affects other synovial joints like knee and elbow, but it has been described at the TMJ in many instances (almost 200 cases), with a slightly increased female-to-male ratio and a mean age of 46 years (Lieger et al. 2007; Pinto Jr et al. 2015). Most cases are unilateral but a few bilateral cases have also been reported (Keogh et al. 2002; von Lindern et al. 2002; Guarda-Nardini et al. 2010, Guijarro-Martınez et al. 2011; Shah et al. 2011; Pau et al. 2014).

Etiology of SC is not clearly understood. SC is subdivided into primary SC (not associated with causal factors and considered as more aggressive) and secondary SC (related to a previous trauma/microtrauma or degenerative disease) (Holmlund et al. 2003; Guarda-Nardini et al. 2010). Three phases describe the evolution pattern of SC: in the first stage a metaplasia of the synovial membrane takes place with a proliferation of undifferentiated cells and without free bodies, in the intermediate phase there is a presence of metaplastic nodules with loose bodies, and the third stage is characterized by multiple loose calcified bodies without synovial activity (Milgram 1977; Blankestijn et al. 1985).

The most important imaging finding for SC is the presence of cartilage nodules both in orthopantomogram and CT scan. Calcifications are numerous within the nodules’ outer parts (Fig. 9.3a–d). They may present in various sizes and they will cause capsule proliferation and growth. MRI will show the typical cartilage hyperintensity in T2 and hypointensity in T1 if their size is relevant and if they are not largely calcified (Levine et al. 2016). Joint effusion is usually present. As surgical resection is mandatory, MRI allows to thoroughly carry out pre-operative assessment of the involvement of adjacent structures such as the middle cranial fossa (Lim et al. 2011). Differential diagnosis includes osteoarthritis , osteochondroma , chondrocalcinosis, pigmented villonodular synovitis , and osteochondritis dissecans (Balasundaram et al. 2009).

Fig. 9.3
figure 3figure 3

Synovial chondromatosis of the right TMJ. Orthopantomogram (a) shows multiple small radiotransparent areas in the joint cavity, which are surrounded by calcific margins (white arrow). Reformatted axial (b) and coronal (c) CT scans also display the same globular structures (white arrow) with calcified walls which almost entirely occupy the articular space. Gradient Echo coronal sequence (d) shows the calcifications as clearly hypointense punctiform images (arrow). Courtesy of Prof Ambrosina Michelotti

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9.3.3 Pigmented Villonodular Synovitis

Pigmented villonodular synovitis (PVNS) is a rare, benign but locally aggressive mass which derives from TMJ synovial membrane. Around 100 cases of PVNS affecting TMJ have been reported (Verspoor et al. 2018).

This condition seems to be due to a chronic inflammatory response to an unknown stimulus, or to repetitive joint hemorrhage following trauma (Granowitz et al. 1976; Song et al. 1999; Herman et al. 2009; Damodar et al. 2015).The tumor develops in tendons and joints and it is characterized by a thick synovial membrane with villi and folds or pedunculated nodules (Nomura et al. 2018). Its name is also due to a peculiar hemosiderin deposition which gives a red-brownish color.

As the tumor grows, it can involve surrounding TMJ structures such as the cranial base and the ear canal.

MRI gradient echo sequences will show ferromagnetic artifacts due to hemosiderin deposits. Because of these and because of fibrous tissue and increased cellularity, an overall hypointensity will be found in all sequences, T2 and fat-suppression included.

Differential diagnosis includes tuberculosis septic arthritis, malignant synovioma, hemophilia, rheumatoid arthritis , gout, synovial chondromatosis, parotid tumor, and carcinoma of the external and middle ear.

9.3.4 Aneurysmal Bone Cyst

Aneurysmal bone cyst (ABC) is a rare, osteolytic, pseudocystic, osseous lesion that rarely affects the condyle (unilaterally). Very few cases of condylar ABC have been reported, and other also uncommon oral-maxillofacial cases have been described in young patients under 20 years of age (Kransdorf and Sweet 1995; Motamedi et al. 2008).

Etiology and pathogenesis are still unclear although a history of trauma is often reported (Motamedi 2002; Motamedi et al. 2008). Theories include reactive vascular malformation, vascular incidents within an existing lesion, and genetic predisposition (Cottalorda and Bourelle 2007; Motamedi et al. 2008).

Although benign in nature (they commonly show a slow growth), the lesion can expand rapidly and can be locally both destructive and expansive (Mankin et al. 2005; Liu et al. 2017).

The lesion may appear as a unicystic or multilocular, with an expanding behavior which sometimes extends to soft tissues. Perforation of cortical bone may accompany ABC growth (Motamedi et al. 2008).

9.3.5 Ganglion Cyst

Ganglion cyst is a benign lesion that occurs near joints (wrist, foot, shoulder, and knee are the most affected sites) and rarely affects the TMJ.

Unlike synovial cysts, which are true cysts lined with endothelial cells and filled with synovial fluid, ganglion cysts are not related to the joint space and they contain a highly viscous gelatinous protein material with an acellular fibrous tissue inner lining (Algharib et al. 2015).

Etiopathogenetic explanation for this pseudocyst is that it develops from a myxoid degeneration of the collagenous tissue of the joint capsule (Goudot et al. 1999; Silva et al. 2005; Ali et al. 2006; Lee et al. 2014; Algharib et al. 2015; Levarek and Nolan 2016).

Most cases are unilateral and unilocular. Differential diagnosis includes synovial cysts, salivary gland tumor, sebaceous cysts, and condyle malignancies (Yanagi et al. 2003; Silva et al. 2005; Solomon et al. 2008; Algharib et al. 2015).

9.3.6 Calcium Pyrophosphate Dihydrate Deposition Disease

Calcium pyrophosphate dihydrate deposition disease (CPDD) , also known as pseudogout, is a rare crystalline arthropathy caused by the deposition of calcium pyrophosphate crystals in the joints (Grant et al. 1999; Steinbach and Resnick 1996). Abnormal deposition of pyrophosphate on collagen fibers activates the release of inflammatory mediators, which cause an articular damage known as chondrocalcinosis (Marsot-Dupuch et al. 2004).

CPDD arthropathy is often associated with other medical conditions including trauma, gout, hemochromatosis, hypomagnesemia, hypophosphatemia, hypercalcemia, hyperparathyroidism, Wilson’s disease, and alkaptonuria (Steinbach and Resnick 1996). It may sporadically occur on a hereditary basis too (Abhishek and Doherty 2016).

Causes of chondrocalcinosis are not currently known. The fact that pseudogout is frequently associated with other pathological conditions and with an advanced age (about 50% of subjects over 85 years of age are affected by chondrocalcinosis) suggests that the deposition of calcium pyrophosphate crystals are secondary to the degenerative or metabolic phenomena of the affected tissues (Steinbach and Resnick 1996; Marsot-Dupuch et al. 2004; Reynolds et al. 2008).

CPPD may be associated with various chronic and acute symptoms or it may be unnoticed (McCarty and Hollander 1961; Molloy and McCarthy 2006). The joints most commonly affected are the shoulder, knee, hip, elbow, and metacarpophalangeal joints, while axial skeleton involvement (both spinal and cranial) is less common (Grant et al. 1999; Steinbach and Resnick 1996; Marsot-Dupuch et al. 2004; Reynolds et al. 2008). TMJ involvement has been reported to present with pain, swelling, and hearing loss (Marsot-Dupuch et al. 2004; Scavarda et al. 2007).

Several clinical presentations of CPPD in the joints exist, which include totally asymptomatic to acute inflammatory arthritis (pseudogout), chronic degenerative arthritis (pseudo-osteoarthritis), or chronic symmetric inflammatory polyarthritis (pseudorheumatoid arthritis) (Reynolds et al. 2008). Presentation of CPDD in the form of a ‘‘tumor-like” mass has been indicated with the term tophaceous pseudogout. This is a clinical variant of CPPD, associated with swelling and pain of involved joints. Tophaceous pseudogout is more frequently found in large joints. Small joints such as the TMJ can be affected too, albeit more rarely (McCarty and Hollander 1961; Scott 1978; Resnick and Niwayama 1988; Ishida et al. 1995; Kurihara et al. 1997; Reynolds et al. 2008; Aoyama et al. 2000). CPPD of the TMJ may mimic tumors, gout, and synovial chondromatosis both clinically and radiographically and an open biopsy is usually recommended to make a correct diagnosis (Kurihara et al. 1997; Aoyama et al. 2000; Barthelemy et al. 2001; Marsot-Dupuch et al. 2004).

Highest specificity imaging for calcium pyrophosphate dihydrate deposition disease (CPDD) is provided by CT, which is capable of showing a large fossa-occupying mass with small synovial calcifications made of calcium pyrophosphate dihydrate (CPP) crystals. Again, because of these crystals, an inflammatory response is triggered with activation of neutrophils and macrophages and release of inflammatory mediators (Srinivasan 2012). Special aggressiveness of this tissue can lead to erosion of the temporal bone, of the greater wing of the sphenoid bone and of the mastoid air cells (Fig. 9.4a–c) (Srinivasan 2012; Kudoh et al. 2017).

Although MRI can well define CPDD TMJ synovitis, it cannot show the small synovial calcifications that expand the joint and erode bone nearby as precisely as CT scan (Fig. 9.4a–e). As the whole joint is occupied by an expanding mass, chondrocalcinosis of the TMJ is usually to be differentially diagnosed from synovial chondromatosis and chondrosarcoma (Kudoh et al. 2017). Synovial chondromatosis is characterized by a diffusely hypointense synovial tissue (in T1–T2 weighted images), that occupies the joints space, or by globular formations (Murphey et al. 2007). The latter have different shape and size according to the degree of synovial cartilage metaplasia and synovial ossification. Chondromatosis free bodies usually present with larger calcifications than those seen in CPDD (Abdelsayed et al. 2014).

Fig. 9.4
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CT images showing deposits of calcium pyrophosphate crystals within the synovial tissue which occupy the joint (a, b, star). Erosions involve the condyle (a, arrow), the temporal bone (b, c, arrows), and the middle ear (b, star). Sagittal Gradient Echo T2 fat sat (d, arrow) and coronal SE T2 (e, arrow) both show synovitis within the joint space. Calcifications, that are typically well visible in CT scans, can be seen as hypointense bodies in Gradient Echo sequences (d)

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9.4 Clinical Presentation and Management

TMJ tumors show nonspecific symptoms and may mimic other TMJ disorders. Signs and symptoms are related to tumor dimension and its main vector of growth. As the tumor enlarges, subjects can go from being asymptomatic to complaining about limitation during jaw movements, pain, ipsilateral open-bite, chin and midline deviation toward the non-affected side, swelling in the preauricular region and joint sounds (Siar et al. 2004, Dhirawani et al. 2014). In larger tumors, an increase in vertical dimension of the condyle may also lead to remarkable progressive facial asymmetry. Because of this, clinical suspicion of more common conditions such as condylar hyperplasia is justified (Wolford et al. 2014).

In locally more aggressive histotypes, the mass can cause swelling, bone erosion, hearing impairment, skin auricular symptoms (otalgia, hearing loss, tinnitus, otitis media, otorrhea), preauricular paresthesia, and facial nerve palsy (Albright et al. 2000; Ali et al. 2006; Mumert et al. 2012; Roman-Ramos et al. 2017).

Pathological fractures of the condyle may occur and they have been described mostly in case of malignancies and cystic lesions (Motamedi 2002; Jia et al. 2006).

Treatment choice depends on histotype, tumor extension, local aggressiveness, and on patient characteristics such as degree of impairment and age. Surgical therapy allows for final diagnostic histopathology and it may range from simple curettage to resection and TMJ reconstruction (Wu et al. 2011; Savolainen and Kellokoski 2013; Liu et al. 2017).

For less aggressive, slow-growing tumors, surgical excision is generally the most common approach, although for small indolent lesions a wait-and-see strategy may be used (Chandu et al. 1997; do Egito Vasconcelos et al. 2007).

For particular tumor-like lesions, arthroscopy may prove useful both for diagnosis and treatment. However, if mass growth is significant or the number and size of loose bodies are unfavorable, open surgery is the best option (Guarda-Nardini et al. 2010).

For more aggressive, larger tumors, resective surgery is required followed by TMJ reconstruction (Zachariades 1989; Zavattero et al. 2013; Jiao et al. 2015; Mehra et al. 2016). When indicated, resection has to be wide enough to improve prognosis and avoid recurrences (Garzino-Demo et al. 2010). Nowadays wide resections are not as disabling as they used to be, given that reconstructive techniques have evolved and have been implemented. Adjuvant therapies (radio- immuno- and chemotherapy) may also be needed.