Intra-articular tenosynovial giant cell tumor is a type of tenosynovial giant cell tumor that typically occurs in the synovial tissues of large joints. It is also known as pigmented villonodular synovitis (PVNS). PVNS have localized (nodular) and diffuse variants, classified on the basis of the extent of synovial or tenosynovial involvement [1]. The localized (nodular) and diffuse forms are both identical histologically. However, in 2007, Rubin had recommended the use of the term tenosynovial giant cell tumor for nodular lesions [2]. Although tenosynovial giant cell tumors are extra-articular lesions and mostly arise from tendon sheets, intra-articular nodular lesions arising from joint synovium have similar histological characteristics. Thus these intra-articular lesions are termed as Intra-articular tenosynovial giant cell tumors.

PVNS has bimodal distribution. They mostly seen in second and fifth decade of life and has an estimated incidence of 0.0002–0.0008% [3]. Most common location for PVNS in children is the knee, ankle is the second and the hip comes later [4]. Insidious onset of pain, swelling of the joint and limitation of ROM are common clinical findings in children as well. However, plain radiographs are unremarkable in most children and acute onset of the pain with irritable hip symptoms is very rare. In this paper, we presented two adolescents with acute onset of hip pain mimicking septic arthritis diagnosed with intra-articular tenosynovial giant cell tumor.

The differential diagnosis of acute onset of hip pain in a child with uncertain laboratory findings include; septic arthritis, periarticular infections, transient synovitis, Legg-Calve-Perthes disease, synovial chondromatosis, and juvenile idiopathic arthritis [5]. No current data exist about the incidence of PVNS in children, but it is estimated to be substantially lower than in the general population [3]. Hip involvement is rare both in adults and children. Tenosynovial giant cell tumor is usually presented with insidious joint pain, swelling, limited joint function and soft tissue mass [6]. The mean duration of symptoms before presentation for PVNS in a study of 166 cases have been reported to be 10 months for nodular intra-articular disease, and no patients in that group had presented with acute symptoms [7]. Our literature review revealed nine cases from four case reports and one case series reporting hip involvement in children [1, 4, 5, 8, 9]. Of these, only four cases had intra-articular tenosynovial giant cell tumor hip involvement presenting with acute irritable hip symptoms (Table 1).

Regarding the radiological investigations, MRI plays an important role in diagnosis, staging, preoperative planning and clinical follow-up of synovium based lesions. PVNS is observed as a mass or mass-like synovial proliferation on MRI. T1 and T2 signals of lesions vary low to intermediate (according to concentration of hemosiderin) and predominantly high-signal is seen in short tau inversion recovery sequence. Differential diagnosis includes rheumatoid arthritis, hemophilic arthropathy, septic arthritis, tuberculosis, and synovium based neoplastic processes. Gradient echo images (GRE) can be very useful to differentiate these entities when combined with laboratory surveys. IATGCT lesions show typically low signal in GRE sequence and magnetic susceptibility (blooming) artifacts can be seen due to hemosiderin depositions [6].

The reason for acute inflammation and irritable hip symptoms is unknown. Saadat et al. [8] had hypothesized that the trauma may have caused the torsion/bleeding and/or infarction of the nodular lesion which may be the reason for hemarthrosis in their case. Early coagulative necrosis (infarction) after torsion may also have played a role in neutrophil chemotaxis. Thus, the neutrophil recruitment may have contributed to the fever, acute pain, and other clinical features of a septic hip. However, for our cases, there was no trauma, In case 1, the joint aspirate was of light serohemorrhagic character, like the fluids aspirated in knee PVNS cases. The fact that the patient’s complaints developed gradually within 5 days suggests that neutrophil attack may have caused inflammation of the lesion, and therefore an increase in joint fluid, leading to acute irritable hip findings. In case 2, the joint aspirate was of dark haemopurulent character because aspiration was done under fluoroscopy but not ultrasound, we may have aspirate from the center of the lesion. In addition, the pedicle of the lesion was so thin (1 mm wide and 3 cm long) that it could be torsioned with a very simple movement. In a lesion with such a thin pedicle, venous stasis and infarct can easily develop not only with torsion but also with mild inflammation. Similar to the pathophysiological processes that cause the development of osteomyelitis in the metaphyseal region of the bones in children, venous stasis may lead to development of a suitable breeding environment for bacteria and septic arthritis. 64,000 leukocytes, 95% of which are neutrophils, in the aspirate of the second case supports this theory. Causative bacteria can be detected in cultures in approximately 30-50% of patients in septic arthritis cases [10]. In the second case, although Gram-negative bacteria were observed in gram staining, it was considered as contamination since it was not a typical organism in adolescence and there was no growth in the culture. However, since recent studies have shown that gram-negative bacteria (especially kingella kingae) is the most common cause of septic arthritis under 4 years of age [10], this case was evaluated and treated as an infected intra-articular tenosynovial giant cell tumor in which the causative organism could not be identified.

The differentiation of diffuse and nodular forms is important as nodular and diffuse forms of the condition behave and appear differently. Diffuse form develops more insidious complaints probably leading to late diagnosis of the disease, behaves more aggressive and has a more tendency of recurrence. Late diagnosis, recurrence after resection and aggressive behavior of the diffuse form causes early articular degeneration and joint narrowing [3]. Thus, open or arthroscopic subtotal resection of the synovium remains the treatment of choice for diffuse form. Although some authors had performed arthroscopy to resect these lesions because of less invasive nature of arthroscopic technique and better visualization of the particularly hip joint, the efficacy of arthroscopic synovectomy has only been shown for the knee joint [11]. Contrary to diffuse form, TGCT have a tendency to cause episodic effusions and behave less aggressively and previous literature had showed that arthroscopic excision is effective for IATGCT for shoulder, hip knee, and ankle joints [11, 12]. Of the five cases that had been reported to present with hip symptoms, two had operated through an open approach, six had operated with arthroscopy, and one had followed by conservative means [1, 4, 5, 8, 9]. Only resection of the lesion had performed in operated cases as authors had reported that the lesions to be connected to the synovium with relatively narrow pedicles which enabled the resection of the lesion. We preferred an anterior open approach as this approach enables easy resection of the anteriorly localized lesions, debridement, and irrigation of the joint. However, for a posterior or medial localized IATGCT arthroscopic resection is recommended treatment modality [11].

Although intra-articular tenosynovial giant cell tumor is a rare disease of the pediatric population involving the hip and the acute presentation is very rare to be seen, this diagnosis should be kept in mind mainly in cases with serohemorrhagic aspirate and unequivocal laboratory findings.

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