Presentation
Right arm swelling
Patient Data
Right arm posterolateral intramuscular irregular and infiltrative soft tissue mass lesion infiltrating the brachialis and the lateral head of the triceps muscles. The lesion elicits heterogeneous low/intermediate T1, high to intermediate T2, and STIR signal with internal bands of low signal. It is seen partially encircling the humeral shaft with no evidence of cortical invasion, marrow infiltration or periosteal reaction. The related subcutaneous tissue shows soft tissue stranding and scarring.
Pathology
Specimen
US guided core biopsy
Gross
Multiple cores, totally submitted
Microscopy
The examined sections revealed growth portion showing sweeping fascicles of elongated, slender spindle cells with frequent wavy nuclei, lacking cytological and nuclear atypia , set in a collagenous stroma. No malignancy.
Diagnosis
Benign spindle cell neoplasm favoring fibromaosis
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
- feathery margins mainly along its upper and lateral aspect resembling afire giving the (flame sign)
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