Mediastinal monophasic synovial sarcoma with vertebral metastases: A case report

Abstract

Mediastinal monophasic synovial sarcoma is a rare subtype that often lacks specific imaging characteristics, posing diagnostic challenges. This case report describes a mediastinal monophasic synovial sarcoma with vertebral metastasis, emphasizing imaging findings, differential diagnosis, and pathological features, thereby providing crucial support for accurate diagnosis and treatment planning.

Keywords: mediastinal; metastases; monophasic synovial sarcoma; rare; surgery.

FIGURE 1

The enhanced scan of first computed tomography (CT) and magnetic resonance imaging (MRI) was admission: (A) The CT scan showed a right paravertebral mass at the level of the 8th and 9th thoracic vertebrae. (B) Enhanced CT scan showed marked inhomogeneous enhancement of the lesion, which is poorly demarcated from the right thoracic erector spinae muscle, with swelling and hypodensity of the right thoracic erector spinae muscle, and flocculent enhancement is seen within it (red arrows in A and B). MRI: (C) The T1WI sagittal lesion was isosignal with small patches of mixed high signal seen within it. (D) T2WI sagittal showed mixed signals with predominantly high signals. (E) T2WI cross‐sectional compression fat showed mixed signals of high and low with slightly high signals, and the lesion partially protruded into the spinal canal at the level of the thoracic 7 and 8 vertebrae, with compression of the spinal cord, and localized bone destruction of the right 8th and 9th posterior ribs and the right transverse process of the thoracic 8, with distended changes in the 9th posterior rib (red arrows in C, D and E). (F) Emission computed tomography (ECT) showed right 8 and 9 posterior ribs with localized concentration of bone nuclei and normal distribution of nuclei in the rest of the skeleton.

FIGURE 2

Ultrasound puncture biopsy of pathological tumor cells considering monophasic synovial sarcoma. (A) Microscopy (10 × 10) showed densely distributed short spindle cells with slit‐like structures and areas of the stroma exhibited myxoid changes. (B) tumor cells were stained by IHC and were focally positive for CD99.

FIGURE 3

Preoperative MRI scanning with enhancement shows a mass‐like mixed signal shadow measuring approximately 2.42 cm × 1.37 cm. (A) The lesion was isosignal in the sagittal position of T1WI. (B) T2WI transects showed mixed high and low signals with predominantly high signals. (C) T2WI sagittal pressure lipids showed iso‐hypermixed signals with predominantly high signals. (D) T1WI transverse enhancement scan of the lesion showed marked inhomogeneous enhancement, within which streaks of unenhanced areas were observed (red arrows in A, B, C, and D).

FIGURE 4

Six months postoperative follow‐up: (A) CT plain scan showed that some of the right‐sided arch boards of thoracic 8 and 9 and the right‐sided transverse processes, localized bony defects of the right‐sided 8th and 9th ribs show postoperative changes, and soft tissue thickening of the right‐sided trapezius and erector spinae muscles; (B) CT enhancement scan showed no abnormal enhancement (red arrows in A and B). Twelve months postoperative follow‐up: MRI showed a right paraspinal mass‐like mixed‐signal shadow at the level of thoracic 8 and 9 vertebrae; (C) T1WI sagittal lesion was isosinusoidal; (D) T2WI sagittal was isosinusoidal with a predominantly slightly higher signal; (E) T2WI sagittal compression lipids showed predominantly high signal with isohyperintense signal, and the lesion was poorly demarcated from the right thoracic erector spinae muscle. (F) T1WI sagittal enhancement scans of the lesion showed marked inhomogeneous enhancement, with small strips of unstrengthened areas within it, and the boundaries were poorly defined (red arrows in C, D, E, and F).