Discussion

Tumoral calcinosis

Tumoral calcinosis should not be confused with Teuschlander's tumoral calcinosis, also known as Inclan's calcinosis, which, although long classified as an idiopathic calcinosis, is now considered a genetic disease.

In the literature, the average time of appearance of the mass after the start of dialysis seems to be widely variable, from a few months to several years. Clinically, the lesions present as pseudotumor masses of usually slow evolution, up to 20 or 30 cm in diameter. They are most often located in the vicinity of large joints (hips, knees, shoulders, elbows) and sometimes on the extremities. Pubic involvement is rare. The skin is usually normal in front of the lesions, which are usually asymptomatic. Much more rarely, they may fistulate to the skin, limit joint movement, or cause nerve or vascular compression. Lysis of the surrounding bone structures by calcinosis is exceptionally reported. The observation of tumoral calcinosis presented here is therefore unusual not only because of its location but also because of its local aggressiveness (pubic osteolysis).

Although the pathophysiology is not fully elucidated, the increase of the phosphocalcic product beyond the precipitation threshold (> 70) and the more than severe hyperparathyroidism seems to play a determining role. Indeed, several cases of tumoral calcinosis have already been reported without associated hyperparathyroidism or after parathyroidectomy. In patients with chronic renal failure, there is a defect in phosphorus filtration responsible for an increase in intracellular phosphates and hyperphosphatemia. Hypocalcemia is associated with a relative deficit in vitamin D, mainly due to a defect in renal 1-hydroxylation. These disorders (hypocalcemia and hyperphosphatemia) stimulate the production of parathormone (PTH), leading to secondary hyperparathyroidism.

On radiographs, the lesion is multilocular, para-articular with clustered juxtaposition of small, dense, rounded or oval images, well limited by a ring, with a more or less opaque homogeneous content depending on the density of calcium crystals, and sometimes a liquid level within an elementary formation related to the sedimentation of calcium crystals with serous supernatant (sedimentation sign). Erosions of the bone cortex adjacent to the calcinosis are rarely described. The CT scan shows the local extension of the tumor. The ultrasound appearance has been poorly described in the literature; the lesions present as multiloculated masses with a calcified peripheral shell and fluid content.

On MRI, in T1-weighted sequences, tumoral calcinosis appears mostly hypointense due to the calcific nature of the tumor and the peritumoral edema, and in T2 a nodular heterogeneous hyperintensity predominates, related to the inflammatory reaction associated with areas of low intensity reflecting calcium deposits. Bone scintigraphy allows the early detection of these deposits and the assessment of their progressive nature. Destruction of the adjacent bone may be the result of erosion due to repeated microtrauma to the bone caused by the large size of the mass and its periarticular location.

In the presence of radiographic evidence of bone destruction, a neoplasia such as chondrosarcoma should be included in the differential diagnosis. A sedimentation sign, most often appreciated on CT scan if detected, is helpful in establishing the diagnosis of tumoral calcinosis.

The treatment of tumoral calcinosis is difficult. Surgical removal of the calcified mass is controversial. It seems to be indicated mainly in compressive forms. When it is performed, it must be as complete as possible in order to avoid recurrence.

Medical treatment aimed at balancing the phosphocalcic product is essential (e.g., phosphorus binders, hypoprotein diet, dialysis baths low in calcium).

When secondary hyperparathyroidism is associated, parathyroidectomy can give spectacular results. However, tumoral calcinosis has been observed in subjects who have previously undergone parathyroidectomy, suggesting that such a procedure should only be considered for severe hyperparathyroidism with normo or even hypercalcemia and very high PTH. Dramatic regression of PTC after renal transplantation has also been reported.

The existence of this rare condition seems to us to be important to recall in order to evoke it rapidly when confronted with a deep cutaneous lesion of tumoral appearance in a chronic hemodialysis patient, as alternatives to surgery are possible and most often desirable.

Learning points

• Calcinosis of chronic renal failure is a rare cause of soft-tissue calcifications in hemodialysis patients with chronic renal failure.
• It should not be confused with primary tumoral calcinosis, which is a rare familial condition characterized by painless, periarticular masses in young patients with normal kidney function.
• This condition is characterized by the deposition of calcium phosphate crystals in the periarticular soft tissues, resulting in large, calcified masses.
• CT better delineates the calcific mass and may show a cystic appearance with multiple fluid-calcium levels caused by calcium layering (sedimentation sign).

References

View the original case report for a complete list of references.

Our appreciation is extended to Dr. Youssef Sakhy, Ibn Rochd University Hospital, Casablanca, Morocco, for contributing this case. Case was originally published in BJR|case reports.