Teaching Case

A 10-year-old male child presented with complaints of painless progressive swelling over the right hip since 2 months. He had similar swellings in the right index finger and elbow. The swelling over the right elbow had been operated before, but there was a recurrence. There was no history of trauma, fever or weight loss.

Radiograph of right hip joint (Fig. 1), showing a large multiglobular calcific mass overlying the hip joint, with some globules showing fluid-calcium levels, termed “sedimentation sign”. Radiographs of right elbow (Fig. 2) and right hand (Fig. 3) showing soft tissue calcifications along the extensor aspect of elbow and radial aspect of terminal phalanx of 1st digit. Underlying bones and joint were normal.

T1 weighted axial MR image (Fig. 4) showing heterogeneous isointense encapsulated soft tissue mass in the subcutaneous plane around the hip joint, displacing and insinuating between the gluteal muscles. T2 weighted (Fig. 5) and STIR images (Fig. 6), showing heterogeneous, multiloculated, predominantly hyperintense cystic mass with some cysts showing “shading” and “fluid levels”. The septations between the cysts are iso to hypointense. On post contrast imaging (Fig. 7), these septae show marked heterogeneous enhancement with solid enhancing areas suggestive of “pseudo-tumoral” appearance. Gradient sequence (Fig. 8) shows areas of blooming in septae.

Tumoral calcinosis is strictly speaking a disease caused by a hereditary metabolic dysfunction of phosphate regulation associated with massive periarticular calcinosis [1]. It is characterised by the presence of large calcified soft tissue masses around the joints.

On histopathology, the masses are multiloculated cysts with walls composed of dense fibrous tissue and containing a viscous semifluid suspension of calcium triphosphate or carbonate salts in albumin [2].

The diagnosis of tumoral calcinosis is one of exclusion [3].

Radiographs show a typical imaging appearance of amorphous, multilobulated calcifications which can demonstrate fluid-calcium levels, termed “sedimentation sign” [1]. Osseous destruction of adjacent bones is distinctly absent [1].

On MR imaging two distinct patterns have been observed (a) a diffuse, lower-signal-intensity pattern or (b) a bright, nodular pattern with alternating areas of high signal intensity and signal void [1].

In our case, “bright nodular pattern” was observed which can be explained by high signal intensity of the supernatant fluid on T2 weighted images while the calcium sediment produces a low signal intensity [3]. The isointensity to hypointensity of the septae on T1 and T2 weighted images with blooming on Gradient sequences could be explained by the calcium incrustations along the inner layers [3]. Marked enhancement of the septae and capsule is due to the connective tissue with varying degrees of vascularization and inflammatory reaction [3].

Pseudo-tumoral appearance of enhancing areas, which are hypointense on T1 weighted images and heterogenous signal intensity on T2 weighted images with marked post-contrast enhancement could be due to collapsed cyst walls [3].

In conclusion, tumoral calcinosis is a rare benign entity occurring due to phosphate metabolic dysfunction, resulting in large soft tissue masses with areas of calcification predominantly along the extensor aspects of large joints.

MR imaging is useful to demonstrate the location, extent and relationship of the calcifications with adjacent structures. MR imaging may show unusual signal characters like heterogeneous hyperintensity of the cysts & intensely enhancing pseudo-tumoral areas and septae which can be mistaken for other conditions.

Correlating the radiographic findings and knowledge of these varied MR appearances, along with clinical history and blood parameters helps in narrowing down the differentials and arriving at the correct diagnosis.