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.