Presentation
Left flank mass for three years. Progressively increasing in size, and becoming painful over the last three months. Associated with restricted movements. No history of trauma, fever, or weight loss.
Patient Data
Well-defined, mildly heterogeneous, low echogenicity lesion in the subcutaneous soft tissues of the left lower posterior lumbar region. No demonstratable hyperemia.
A large well-defined oblong-shape non-fatty soft tissue mass is in the subcutaneous tissues between the subcutaneous fascia and left posterior external oblique muscle. It measures 73 x 66 x 40 mm, and is isodense on T1-weighted images, slightly higher than muscle, and heterogeneously high signal on T2 fat-suppressed weighted images. No necrosis, hemorrhage or calcifications are evident. Mild restriction is seen on diffusion-weighted imaging. It shows mildly heterogeneous but avid enhancement on post-contrast images. Multiple non-enhancing low signal intensity fibrous bands are seen in it. It is inseparable from the fascia of the underlying muscle; however, no invasion is seen into the underlying muscle.
Case Discussion
- Imaging differential diagnosis includes peripheral nerve sheath tumor (neurofibroma/schwannoma), fibromatosis, desmoid, or less likely soft tissue sarcoma.
- Ultrasound-guided trucut biopsy: Desmoid-type fibromatosis.
- Wide local excision of the lesion. Final histopathological diagnosis: Desmoid-type fibromatosis, with free surgical margins.
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