A slowly growing painless lump

Excerpt

MRI (Fig. 1a) demonstrated a 1.5 × 1.5 × 3 cm scar-like lesion on the fascia overlying sartorius, which was hypointense on T1-weighted images and demonstrated avid enhancement with minor enhancement of the surrounding fat and muscle (Fig. 1b and c). There was no deep extension or regional adenopathy. On ultrasound (Fig. 2a), the lesion was ill-defined with posterior acoustic shadowing and low level vascularity seen in the periphery of the lesion (Fig. 2b). Excision biopsy was performed and histology (Fig. 3) showed a fascial-based ill-defined stellate lesion composed of fascicles of myofibroblasts and an area of ossification with dilated vessels and an osteoclastic component. The lesion extended to the subcutaneous tissue and skeletal muscle with no significant cytological atypia. CTNNB1 gene mutation analysis by PCR and restriction enzyme digestion (exon 3) was negative for the three most common substitutions (p.T41A, p.S45P and p.S45F), and there was no evidence of malignancy. A diagnosis of fasciitis ossification (FO) was made. …