Calcifying aponeurotic fibroma

Case contributed by Hrishikesh VJ
Diagnosis almost certain


Painless lump in the palmar aspect right wrist of long-standing duration with no limitation of movement.

Patient Data

Age: 13 years
Gender: Male

Poorly encapsulated enhancing soft tissue mass with multiple small T1 and T2 dark intralesional nodules (likely calcific foci) seen in the palmar side of the wrist overlying the scaphoid and trapezium/trapezoid bones, with the lesion surrounding the palmar aponeurosis and located superficial to the transverse carpal ligament.   The lesion encases the abductor pollicis longus tendon at the wrist. No extension into the carpal tunnel. 

A second smaller similar lesion also with intralesional probable calcified nodules seen at the ulnar side palmar aspect of wrist overlying the pisiform bone and deep to the flexor carpi ulnaris tendon.

CT demonstrates the same findings and confirms the presence of intralesional chondroid type calcifications. The absence of bone erosions was noted on CT. 

Case Discussion

The above findings in a pediatric age group in the given location are highly specific for calcifying aponeurotic fibroma, which is a rare benign tumor affecting the fascia (palmar aponeurosis in this case) and tendons and coming under the "musculoskeletal fibromas" spectrum. 

These lesions are composed of numerous fibroblasts and collagen matrix with added chondroid type calcifications. The abundance of fibroblasts gives the tumor unencapsulated locally invasive edges with a high probability of recurrence post excision. Unlike their adult counterparts, palmar/ plantar fibromatosis, contractures developing at the affected site are rare. 

Differential diagnosis includes a tenosynovial giant cell tumor, which is uncommon in the pediatric age group, and the presence of adjacent bony erosions and lack of calcifications can help differentiate the two. Other differentials include synovial chondromatosis of the wrist (a rare location for the disease) and synovial sarcoma.

This child underwent surgical excision of the lesion on the radial side and pathological examination showed numerous fibroblasts arranged around foci of calcifications, which is consistent with the diagnosis of calcifying aponeurotic fibroma. 

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