Table 1 Summary of the clinical, radiological, and pathological features of myositis ossificans-like soft tissue aneurysmal bone cyst.
Patient | Age (years)/sex | Site (size in cm) | Imaging findings | Pathology findings | FISH for USP6 rearrangement | Fusion partner by targeted RNA sequencing | Treatment | Clinical outcome |
|---|---|---|---|---|---|---|---|---|
1 | 32/F | Thigh, subcutaneous tissue (4.0) | Ultrasound: Oval, partially cystic mass with mild peripheral vascular flow; Plain radiograph: (−) Calcification; MRI: Mass with thickened rim compressing and infiltrating the fascia, (+) perilesional edema, (+) fluid–fluid levels | Classic MO-like zonation with an ossified rim and central cystic spaces | Positive | COL1A1 (exon 1)-USP6 (exon 1) | Wide resection | Disease free at 40 months |
2 | 17/M | Supraclavicular soft tissue, juxtacortical (2.3) | CT: Mass with (+) peripheral calcification contiguous with periosteal reaction at the sternocleidomastoid insertion; MRI: (+) Perilesional edema, (+) fluid–fluid levels | Classic MO-like zonation with an ossified rim and central cystic spaces | Positive | COL1A1 (exon 1)-USP6 (exon 1) | Wide resection | Disease free at 5 months |
3 | 46/F | Gluteal region, intramuscular (7.5) | Ultrasound: Solid mass with (+) multifocal calcifications; Plain radiograph: Multiple-clustered calcifications, increased on postbiopsy studies; MRI: (+) Perilesional edema, (−) fluid–fluid levels | Ill-defined, fat-infiltrating fibroblasts with multifocal ossifications | Positive | ANGPTL2 (exon 1)-USP6 (exon 1) | Wide resection | Mass increased in size and symptoms persisted for 38 months prior to resection |
4 | 51/F | Hypothenar soft tissue (2.4) | Plain radiograph: Calcifications (−) at baseline but formed in 2 months; MRI: Lesion with diffuse low T1 and T2 signals and contrast enhancement, (+) extensive surrounding edema and soft tissue thickening, (−) fluid–fluid level | An evolving MO-like lesion with vague zonation, solid | Positive | COL1A1 (exon 1)-USP6 (exon 1) | En-bloc excision | Lost to follow-up |
5 | 22/F | Axilla deep soft tissue (4.7) | Plain radiograph and CT: Mass with (+) peripherally calcified mass, increased on postbiopsy studies; MRI: Mass displacing the brachial plexus and axillary vessels without definitive infiltration, (+) perilesional edema, (+) fluid–fluid levels | Elements of classic MO on biopsy, including blood-filled sinusoids | Positive | COL1A1 (exon 1)-USP6 (exon 1) | Incisional biopsy | Asymptomatic at 55 months |
6 | 14/F | Thigh, juxtacortical (2.9) | Plain radiograph and CT: Lesion with (+) peripheral and internal amorphous calcification, with associated periosteal reaction, increased on postbiopsy studies; MRI: Enhancing lesion in the vastus intermedius muscle, (+) perilesional edema, resolved subsequently, (−) fluid–fluid levels Bone scan: Intense radiotracer uptake, resolved on follow-up studies | Elements of classic MO on biopsy, solid | Positive | COL1A1 (exon 1)-USP6 (exon 1) | Incisional biopsy | Asymptomatic at 16 months |
7 | 42/M | Thigh, intramuscular | Ultrasound: Hypoechoic solid mass beneath the superficial fascia; Plain radiograph: Peripherally calcified mass, increased on postbiopsy radiographs; MRI: Diffusely enhancing mass with no neurovascular involvement, (+) perilesional edema, resolved subsequently and (−) fluid–fluid levels | Elements of classic MO on biopsy, including small blood-filled sinusoids | Negative (limited cells analyzed) | COL1A1 (exon 1)-USP6 (exon 1) | Needle biopsy | Asymptomatic at 3 months |
