Teaching Case

A 12-year-old boy presented with a history of focal swelling over the right hip for the past 8 years (Figure 1). No history of trauma or systemic disorder was present. Local examination revealed multiple, hard masses around the right hip with two sinuses exuding thick paste-like material. Blood phosphorus was mildly raised (7.9 mg/dl)].

A radiograph of the pelvis showed a large multi-lobulated calcific mass in the periarticular location of the right hip joint (Figure 2).

Computed tomography images showed multiple fluid-calcium levels giving a “sedimentation sign” within the periarticular calcific mass (Figures 3a and 3b). There was associated superolateral displacement of the femoral head, likely secondary to the mass effect from the long-standing lesion (Figure 3c).

Pelvic MRI depicted the lesion as a multi-lobulated and multi-septated solid cystic lesion appearing heterogeneously hyperintense on T2-weighted images in the proximal aspect of the right thigh, primarily involving the muscles of the anterior compartment of the thigh. The lesion was seen to be insinuating in the myofascial planes of the medial and posterior compartments with the formation of a sinus tract in the posterior aspect (Figures 4a and 4b). Multiple fluid-calcium levels were seen within the mass (Figure 4c). Minimal synovial effusion present (white dashed arrow), likely reactive effusion caused by mechanical irritation from the adjacent calcific mass.

A biopsy from the lesion at the right hip showed deposits of calcium and foreign body giant cells, consistent with a diagnosis of tumoral calcinosis.

Tumoral calcinosis (TC) is a rare, benign condition characterised by calcific deposits of hydroxyapatite or amorphous calcium phosphate crystals in soft tissues near large joints [1]. It is commonly seen in the first two decades of life [2]. Approximately one-third of patients with TC show familial inheritance [3].

Clinically, it presents as painless, progressive swellings around the joint of insidious onset, predominantly along their extensor aspects. The commonly involved joints include the hip, elbow, foot, and wrist [1]. Constitutional signs and symptoms are characteristically absent.

It is classified into primary and secondary types depending on the presence or absence of an underlying calcifying disease process. The primary variety has two subtypes: a familial hyperphosphatemic type with mutations in GalNAc transferase 3 gene (GALNT3), fibroblast growth factor 23 (FGF23) genes [4], and a normophosphatemic subtype with an underlying mutation in the SAMD9 gene [5]. Chronic renal failure (CRF) is the most common identifiable condition causing secondary tumoral calcinosis.

Imaging plays an important role in diagnosis. Radiography is generally the first line of investigation. The classic tumoral calcinosis lesions are characterised as lobular, densely calcified masses with radiolucent septa giving a multilocular appearance, generally along the extensor surface of the joint. Cross-sectional imaging helps in characterising the morphology, extent of involvement, and determination of its relationship with the musculoskeletal and osseous structures.

On computed tomographic images, the lesion is homogeneously hyperdense or has a lower central attenuation with hyperdense walls and potential fluid-calcium levels known as the “sedimentation sign” [6]. The sedimentation sign and mass effect are typically not present in other calcified pseudotumoral lesions, such as hydroxyapatite deposition, calcific myonecrosis, and myositis ossificans. Osseous destruction and erosions are characteristically absent [1].

Ultrasonography is poorly described in the literature. However, some authors have described lesions as multi-lobulated masses with a calcified shell and fluid content, thus determining the disease activity [7].

On MRI, lesions have variable signal intensity, with a low signal in largely calcified portions and cystic areas with a high signal in T2-weighted sequences. In metabolically active lesions, an alternating high and absent signal MRI pattern is seen due to a prominent inflammatory component.

Treatment is tailored according to the stage of the pathology together with the site, size, and relations of the lesion, as well as the symptoms of the patient. Medical treatment is preferred during the active stage and in cases of secondary tumoral calcinosis.

Written informed consent has been obtained from the patient's legal guardian.