Discussion
Tumoral calcinosis is a rare clinicopathological entity which commonly occurs in the periarticular soft tissue of large joints such as hips (31%), followed by buttock (26%) and upper extremities (15%). In the upper extremities, TC frequently involves the shoulder and elbow, however, the involvement of hand and wrist remain scarce3, 8, 9, 10, 11, 12, 13. Our case presents TC of the extensor indicis proprius tendon. To our knowledge, this is the first case to report TC in the extensor tendon.
Common differential diagnosis of wrist swellings is ganglion cyst, giant cell tumor of tendon sheath and extraskeletal chondroma. Other differentials which may mimic TC, includes tenosynovitis with psammomatous calcifications. Ganglion cyst is a benign condition characterized by mucin filled synovial cyst. It is commonly found on the dorsal aspect of the wrist (70%) arising from scapholunate ligament or articulation. Clinically, both TC and ganglion cyst present as firm painless mass 14. However, they can be differentiated by ultrasound imaging. On ultrasound, TC appears as heterogeneous multiloculated mass with hyperechoic thin septa. Color doppler may detect blood flow in some of these septa 6. On the other hand, ganglion cyst appears as hypoechoic or anechoic well-defined mass with possible septations and acoustic enhancement. No blood flow is detected on color doppler 15.
Giant cell tumor of the tendon sheath (GCTTS) is the second most common soft tissue tumor of the hand. It originates from the synovium of the tendon sheath and is characterized by a slowly growing, usually painless mass 16, 17. Ultrasound can be used as the first method in diagnosing giant cell tumor as it provides valuable information about the tumor’s size, vascularity, and its relation to adjacent structures. GCTTS appears as a solid homogenous hypoechoic mass with detectable vascularity. However, heterogeneity may be seen in minority of the cases 18. On the contrary, on ultrasound, TC appears as heterogeneous multiloculated mass with multiple cavities limited by echogenic thin septa 6. In this case, the ultrasound of the mass revealed a multilobulated and mildly echogenic mass with some vascularity corresponding to GCTTS. Therefore, no further imaging was performed.
Extraskeletal chondroma is benign soft tissue tumor which predominantly occurs in the hands and feet. It presents as a slowly growing mass which results in pain and tenderness. Most are solitary and may be attached to the tendon or tendon sheath. Histologically, it exhibits mature hyaline cartilage arranged in lobules. However, some display calcifications, which mimics TC. Nevertheless, soft tissue chondroma can be distinguished histologically from TC by the presence of cartilage8, 19.
Tenosynovitis with psammomatous calcifications (TCP) is a distinctive variant of idiopathic calcifying tenosynovitis or calcifying tendinitis20. Clinically, TPC presents as a painful mass with predilection to the distal extremities. It usually occurs because of repetitive activity or trauma and is not associated with metabolic abnormalities or family history. Clinically, TC may mimic TCP, however, these two entities are distinguished by histopathological examination. On histopathological examination, TCP is characterized by multiple psammomatous calcifications surrounded by granulomatous infiltrate21. In this case the patient presented with atraumatic painful mass on the wrist with no family history or metabolic abnormalities. All together, these clinical features points toward TCP. However, histopathological examination revealed lobules of calcific material surrounded by histiocytic giant cells with few psammomatous calcifications. Therefore, the final diagnosis was TC.
Clinically, there are three forms of TC: idiopathic, hereditary, and secondary form. The idiopathic form is characterized by onset during the first and second decade of life with a solitary, slowly growing, painless mass. The mass is firmly attached to the underlying structure such as fascia, muscle, or tendon. The familial form is inherited in autosomal recessive manner and characterized by multifocal lesions. It has two variants, hyperphosphatemic and normophosphatemic. The hyperphosphatemic form is distinguiashed from the normophosphatemic form by elevated levels of phosphate and vitamin D. The secondary form is characterized by the presence of diseases which promote soft tissue calcifications such as chronic renal failure, systemic sclerosis, sarcoidosis, and primary hyperparathyroidism 8. Our patient presented with solitary calcification with no evidence of familial inheritance. Furthermore, the blood investigations were normal. Based on the preliminary workup, we indicate the absence of underlying metabolic, endocrine and connective tissue disease. Therefore, our case corresponds to idiopathic form of tumoral calcinosis.
Slavin et al. described the histological development of TC based on three stages. Stage one lesion consists of clusters of foamy histocytes aggregates around blood vessels. These histocytes which are found in tendons and fascia, spread into the nearby tendon, fascia, muscle and skin. These histocytes are transformed into cystic cavities as a result of granular necrosis and degenerative alteration in collagen. Stage two consists of cytoplasmic calcification of the disintegrated histocytes and plate-like calcification of the admixed giant cells. Stage three consists of acellular fibrotic tissue filled with dense basophilic calcification 7. This classification has demonstrated clinical, therapeutic, and prognostic values. Stage one is the active stage and refers to early lesion that only occurs in children. At this stage, the growth is prominent because of proliferative and mitotic activities, resulting in a locally aggressive tumor. Therefore, surgical excision is the mainstay of treatment. On the other hand, stage three, which commonly occur in adults, is unactive. Therefore, it does not require surgical excision unless it cause debilitating symptoms3.
Surgical excision is the mainstay of treatment; however, recurrence is possible 7. Medical therapy with phosphate lowering agents and calcium and phosphate restricted diet may be helpful5, 22. Our patient was treated with complete surgical excision of the mass.