Case presentation

In this study, we present the diagnostic and therapeutic approach of a 25-year-old female patient with a two-year evolution of a CCS in the hand. No comorbidities or family history of STSs were reported. The disease began two years earlier with increased left hypothenar volume, accompanied by mild pain.

On targeted examination, the left hand showed an increase in hypothenar volume, and on palpation, a tumor of approximately 5x3x4 centimeters (cm), soft, not very mobile, not painful to manipulation and without changes in coloration. No functional or neurosensory limitations.

MRI showed findings suggestive of STS, with a solid-appearing, multilobulated lesion observed at the hypothenar eminence, without calcifications, containing hypointense septa (Figure 1A, 1C). It appeared hyperintense on fat-suppressed and gradient-echo sequences, with areas of restricted diffusion and anti-diffusion contrast (ADC) and heterogeneous enhancement after gadolinium administration. The lesion measured approximately 4.8 x 3.4 x 4.9 cm along its anteroposterior, laterolateral, and craniocaudal axes, with an approximate volume of 41 cc. It extended inferiorly into the space between the carpal tunnel and the hamate bone in the lateral palmar septum, anteriorly into the interosseous space encompassing the metacarpals (MTCs) of the fifth and fourth phalanges, and medially anterior to the flexor retinaculum. This lesion caused slight compression and contralateral deviation of the carpal tunnel, predominantly affecting the deep flexor tendons of the fifth finger. These findings, taken together, are suggestive of synovial sarcoma. Based on this, an incisional biopsy (for economic limitations) was taken, and the histopathological report concluded CCS.

Figure 1: Magnetic resonance imaging of the clear cell sarcoma of the handPre-radiotherapy: Multilobulated, predominantly cystic tumor in the hypothenar eminence, with thin hypointense septa, measuring 4.8 x 3.4 x 4.9 cm, extending into the space between the carpal tunnel and the hamate bone in the lateral palmar septum, encompassing the fourth and fifth metacarpals (MTC) in A) coronal and C) axial view. Post-radiotherapy: Tumor with the same characteristics but smaller, measuring 3 x 3.1 x 3.7 cm (previously 1.2 x 3.1 x 4.5 cm), displacing the carpal and cubital tunnel anteriorly, in B) coronal view and D) axial view. The margins of the tumor are marked with orange arrows.

Subsequently, the patient received 25 sessions of 50 Gy external-beam radiotherapy, after which the lesion measured approximately 1.3 x 3.1 x 3.7 cm with an approximate volume of 2 cc. It showed no enhancement after gadolinium administration. The lesion displaced the carpal and cubital tunnels anteriorly without involvement of tendons, muscles, bones, or vascular structures, as evidenced by control MRI (Figures 1B, 1D).

Subsequently, resection of the CCS was scheduled. Under general and regional anesthesia and tourniquet placement, marking was performed with a 2 cm (Figure 2A) margin for en bloc resection, including skin, diaphysis, and base of the third MTC, fourth and fifth MTC completely, and head of the ulna, as well as large, hooked, pyramidal, pisiform and lunate bone (Figure 2B, 2C) with negative margins transoperatively (Figure 2D, 2F) and preserving the neurovascular structures of the first to the fourth finger. During the same surgical time, flexor tendon reconstruction was performed with grafts: thumb flexor longus (FPL) with superficial flexor tendon (FDS), tenorrhaphy of the deep index flexor tendon with the flexor carpi ulnaris (FCU), and opposentoplasty with a tendon graft of the superficial flexor tendon of the fourth finger. Transfers from the common extensor digitorum (EDC) to the extensor digitorum are performed.

Figure 2: Surgical plan and design and post-intervention surgical resection.Pre-intervention A) anterior, B) lateral and C) posterior views of the marked design for resection (tumor limits, dotted line circle) with negative margins (2 cm, outer continuous line circle). Post-intervention D) anterior, E) lateral and F) posterior views of the resection performed. Red arrow: resection margin, yellow arrow: tumor margin limits, green arrow: Bone structures, Black arrow: tumor resected with margins, Orange arrow: tenar eminence muscles.

At the same time, marking was performed on the right leg for the collection of a free osteocutaneous flap (OCF) of the fibula (Figure 3A, 3B). Perforating vessels, lesser saphenous vein, sural nerve, and cutaneous island were identified (Figure 3C). The flap was harvested and the donor area was covered with a partial-thickness graft (Figure 3D, 3E).

Figure 3: Donor site of the osteocutaneous free fibula flap.Pre-intervention marking and design of the osteocutaneous flap in the right leg in A) anterior and B) posterior view. C) Harvested free fibula flap. D) Donor site covered with partial-thickness autograft in D) anterior and E) posterior. Red arrow: cutaneous isle. Green arrow: sural nerve. Black arrow: vascular perforating pedicle. Yellow arrow: donor area covered with partial-thickness graft.

At the level of the hand, ischemic changes in the fifth finger were identified and it had to be amputated within two hours of surgery; this ischemia was probably derived from the extensive tumor resection, which involved the neurovascular components of this finger. The articular facet of the radius for the lunate and head of the ulna was resected, and a retrograde intramedullary nail from the second MTC to the scaphoid and radius was inserted. The fibula was cut obliquely in the middle of its length, respecting the pedicle and a fragment of it was placed at 3° MTC towards the radius to maintain its distance and it was fixed with 0.62 Kirschner wires, performing the same procedure with the 4° MTC towards the radius and both segments of the fibula were joined in the proximal area by cerclage (Figure 4A, 4B).

Figure 4: Hand reconstruction surgery after tumor resection.A) Intraoperative X-ray, showing the positioning of the 0.62 Kirschner wires in anteroposterior view and B) oblique view. C) Vascular microanastomosis, end-to-end, from the ulnar artery to the peroneal artery (black arrow). D) Intraoperative image of the hand reconstruction, showing tenorrhaphy with superficial tendon grafts to the deep flexors (green arrow) and nerve coaptations of the median nerve (yellow arrow) with an ulnar nerve graft to the digital nerves of the first, second, and third fingers and the ulnar collateral nerve of the fourth finger. E) Final postoperative image of the hand reconstruction in anterior view and F) posterior view.

Subsequently, vascular microanastomosis was performed, terminus-terminus from the ulnar artery to the peroneal artery (Figure 4C), terminus-terminal "Y" anastomosis of the concomitant fibular vein to a branch of the lesser saphenous vein, and anastomosis of the lesser saphenous vein to the cutaneous dorsal vein. The digital nerves of the median and ulnar nerves were reconstructed with sural nerve grafts, and tenorrhaphy was performed with grafting of the superficial tendons to the deep flexors and nerve coaptations (Figure 4D). Haemostasis was verified, drains were placed, and the flap was fixed with staples and sutures (Figure 4E, 4F). During his postoperative period, at approximately six hours, the flap became congested and an adjacent hematoma of approximately 50 cc was detected, which was evacuated and subsequently continued without complications. The patient was discharged after a three-day postoperative surveillance. In outpatient follow-up, a small area of the flap periphery at the wrist level suffered necrosis and was managed conservatively with closure by second intention, without complications.

The final histological report detailed a lesion of approximately 6.5 cm (diameter at the widest point, including margins), with free margins. Immunohistochemistry analysis of typical CCS markers such as metal-response element-binding transcription factor (mtf1), tumor suppressor gene p16 and transcription factor sox10 were positive. Fluorescence in situ hybridization (FISH) was positive for rearrangement of the ewsr1 gene, confirming the diagnosis.

The patient was seen as an outpatient for six months after surgery, undergoing rehabilitation therapy (Figure 5) after a strict eight-week immobilization to optimize bone tissue union and consolidation. At that time, she had partial movement in the restored phalanges and there were no recurrences of the sarcoma. However, after this period, the hospital team was unable to maintain further follow-up or contact with her, and assessments such as Disabilities of the Arm, Shoulder and Hand (DASH) [9], Musculoskeletal Tumor Society (MSTS) [10], and grip and pressure strength could not be determined.

Figure 5: Clinical follow-up images six months after surgery.A) Dorsal view, B) Palmar (volar) view, C) radial lateral view and D) ulnar lateral view.