Presentation
Forearm swelling.
Patient Data
Distal forearm inter-osseous soft tissue mass lesion insinuated between the distal radius and ulnar shaft. It measures 2.8x 2.1x 4.2 cm along its max axial and CC dimensions. It elicits heterogeneous low/intermediate T1, high to intermediate T2, and STIR signal with internal bands of low signal. It is seen scalloping the radial shaft.
Findings are suggestive of distal forearm inter-osseous soft tissue fibromatosis.
Pathology
Specimen: US-guided core biopsy, multiple cores, totally submitted
Microscopic features
The examined sections revealed a growth portion showing sweeping fascicles of elongated, slender spindle cells with frequent wavy nuclei, lacking cytological and nuclear atypia, set in a fibromyxoid stroma. Degenerated muscle fibers are included. No malignancy.
Diagnosis
Benign spindle cell neoplasm compatible with fibromatosis
Case Discussion
The case presented typical MRI features of desmoid-type fibromatosis including:
typically a reduced signal on T2 WI secondary to dense collagen and hypocellularity
low signal intensity linear bands corresponding to high collagenous stroma (known as the band sign), however, this sign is not specific as it could be seen in the giant cell tumor of the tendon sheath or myxofibrosarcoma.
Desmoid-type fibromatosis or aggressive fibromatosis is an aggressive fibroblastic tumor.
Desmoid tumors are classified according to their location into:
abdominal wall desmoid
intra-abdominal desmoid
extra-abdominal desmoid