Radiol Oncol 2003; 37(3): 155-9. Unexpected diagnosis for preauricular swelling ­two case reports Goran Roić1, Vesna Posarić1, Ante Marušić1, Igor Borić1, Tomislav Vlahović2, Kristina Vrliček3 1 Department of Paediatric Radiology, Children’s Hospital Zagreb, School of Medicine University of Zagreb; 2 Department of Paediatric Surgery, Children’s Hospital Zagreb, School of Medicine University of Zagreb; 3Pediatric Clinic, Zagreb Clinic Center, School of Medicine University of Zagreb, Zagreb, Croatia Background. Preauricular swelling in children may be associated with a wide range of pathology. The his­tory, clinical presentation and imaging features of such swellings may be non-specific. Sometimes it can be caused by underlying bone lesion. Case reports. We report about two children who were admitted to the hospital with swelling in the preau­ricular region and an unexpected final diagnosis. We found aneurismal bone cyst and central giant cell gran­uloma, respectively. Conclusions. Awareness of such lesions is important to avoid diagnostic errors and a potential misman­agement. These lesions are often difficult to differentiate on the basis of their radiographic features alone. A high-resolution US enables an accurate analysis of soft tissue and helps in the differential diagnosis. It also enables an accurate location of the lesion, which helps to avoid a wrong interpretation based on the clinical finding only. The CT-scan performed afterwards provides necessary information for the assessment of lo­cation, structure and size of the lesion. Key words: bone cysts, aneurismal - ultrasonography; granuloma, giant cell; tomography, X ray computed Received 7 July 2003 Accepted 10 August 2003 Correspondence to: Goran Roić, M.D., Department of Paediatric Radiology, Children’s Hospital Zagreb, School of Medicine University of Zagreb, Klaićeva 16, 10 000 Zagreb, Croatia; Phone: +385 1 4600 231; Fax: +385 1 4826053 / +385 1 4600169; e-mail: goran.roic@ zg.hinet.hr Introduction The aneurismal bone cyst (ABC) and central giant cell granuloma (CGCG) of the jaws are usually seen involving the posterior mandible.1-3 Due to their preauricular loca­tion they can be confused with other lesions presented as preauricular swelling such as lymphadenitis or parotitis. The imaging fea­tures, both the ultrasound (US) and comput­ed tomography (CT), of these mandibular le­sions are helpful in establishing a differential diagnosis, although microscopic tissue evalu­ation is generally necessary to accurately identify the lesion. Case 1 An 11-year old male child was admitted with signs of the swollen right preauricular region with light pain and leukocytosis. It was treat­ed as parotitis or lymphadenitis and antibi­otics were prescribed. After the therapy, the swollen area was still obvious; a fine needle aspiration biopsy (FNAB) was performed and it showed a mass of old and new erythrocytes, phagocytes, cy­tophages and some multinuclear histiocytes ­the differential diagnosis was cavernous hae­mangioma or hemorrhagic cyst of the parotid gland. FNAB was repeated two more times and each time the same findings were found. Two months later, when the swollen area showed no signs of the retreat, US and CT were preformed. US showed a complex mass containing anechoic areas separated by fibrous tissue (Figure 1). Precontrast CT (GE Sytec 3000) showed the expansive cystic mass of the processus condylaris of the mandible with multiple flu­id-fluid levels, suggesting the diagnosis of ABC. Contrast CT scans showed the enhance­ment of the septa, which helped to delineate them from the fluid they contain (Figure 2). The segmental resection of the jaw was fol­lowed by the orthodontic treatment. Case 2 A 9-year old boy complained of the pain and swelling of the right preauricular region, one week after a slap to the face. US examination showed the expansive soft-tissue mass of the processus condylaris of the mandible (Figure 3). Laboratory tests showed normal calcium, phosphorus, and alkaline phosphatase levels, a normal parathyroid hormone level (PTH), and no circulating PTH-related peptide (PTH­rP). Radiol Oncol 2003; 37(3): 155-9. Contrast-enhanced CT scans confirmed the presence of expanding soft-tissue mass replac­ing processus condylaris of the mandible with cor­tical expansion and thinning (Figure 4). A biopsy of the lesion confirmed the typi­cal histological appearance of a CGCG of the processus condylaris of the mandible. Although the parents of the child were familiar with the destructive nature of the tumour, they re­fused the operation, so the calcitonin treat­ment was commenced (100 IU or 0.5 mg of subcutaneous human calcitonin per day). Thirteen months after ceasing treatment there was no evidence of further growth. The lesion was filled with a soft, gritty bone. Discussion ABC is an erosive lesion of the bone, most commonly located in metaphysic of long bones and vertebral column in patients under the age of 30. Those that occur in jaws are rare, mostly involving the posterior part of mandible.2,3 The cause of ABC is not fully set­tled. The aetiology is thought to be secondary to the increased venous pressure with haem­orrhage that causes osteolysis. More often they are a reactive process, secondary to trau­ma or vascular lesion, caused by tumour or vascular malformation. Also ABC may repre­sent a primary bone abnormality.2 Patients often have a history of pain and swelling, usually of less than six months du­ration.2 CT scanning will define the lesion and is especially valuable for those lesions lo­cated in areas in which bony anatomy is com­plex, and which are not adequately evaluated by plain films.5-7 On the pathologic examination the underly­ing bone is replaced by cavities of various size filled with blood or/and proteinaceous materi­al. ABC can heal spontaneously after curettage and bone grafting, surgical removal or after se­lective arterial embolization.8-10 The removal of extensive mandibular and maxillary tu­mours is associated with the need of surgical tissue repair and prosthetic rehabilitation, and in young patients the surgical treatment must be followed by the orthodontic one.11,12 Radiol Oncol 2003; 37(3): 155-9. CGCG is a benign destructive bone lesion of the unknown ethiology. It represents 7% of benign lesions of joins, mostly involves parts of mandible and maxilla. It is of variable size and rate of progression, therefore some au­thors think that there is a spectrum of lesions that vary from the relatively benign CGCG of the jaws to the giant cell tumour of long bones, which may represent a low-grade sar­coma.13 The histological similarity of the CGCG to the »brown tumour« of hyperparathyroidism suggests the presence of an unidentified, cir­culating, PTH-like hormone. Microscopically, the lesion shows a collagenous stroma con­taining spindle cells and numerous multinu­cleated giant cells. An identical histological appearance can occur in the »brown tumour« of hyperparathyroidism, ABC and in cheru­bism. Due to the marked polymorphism a his­tological diagnosis of odontogenic tumours is often difficult, therefore, the correlation be­tween clinician, radiologist and pathologist is especially important. A number of the lesions did stabilize or decrease in size and, if they were explored, a fibrous tissue scar was found in many cases.14 However, it is gener­ally thought that most CGCG are not repara­tive and are in fact destructive and will progress if not treated. The treatment of the CGCG lesion is generally surgical and con­sists of curettage or resection, which may be associated with the loss of teeth and, by younger patients, the loss of dental germ.14 A resection is done by recurrent or more ag­gressive variants. Based on histological simi­larity between the CGCG and the »brown tu­mour« of hyperparathyroidism, Harris sug­gested that the CGCG might respond to cal­citonin, even though there was no biochemi­cal evidence of parathyroid disease.15,16 Although most commonly caused by parotitis or lymphadenitis, the swelling in the preauricular region in children may be a re­sult of mandibular lesion (posterior area of the mandible) as it was a case in our patients. It is our opinion that, to establish an early di­agnosis and begin with the treatment on time, an US examination of the preauricular swelling in all patients seems not only rea­sonable, but also necessary. A high-resolution US enables an accurate analysis of soft tissue and helps in the differential diagnosis. It also enables an accurate location of the lesion, which helps to avoid a wrong interpretation based on the clinical finding only. The CT-scan performed afterwards provides neces­sary information for the assessment of loca­tion, structure and size of the lesion. These le­sions are often difficult to differentiate on the basis of their radiographic features alone. References 1. Kaffe I, Ardekian L, Taicher S, Littner MM, Buchner A. Radiologic features of central giant cell granuloma of the jaws. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1996; 81(6): 720-6. 2. Laor T, Jaramillo D, Oestrich AE. Musculoskeletal system in practical paediatric imaging. 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