CRA36 A CASE OF GIANT ANCIENT POSTERIOR MEDIASTINAL SCHWANNOMA

Sze Wei Lim, Noor Izyani Zakaria, Shivaanand A/L Letcheminan, Wan Jen Lye

Respiratory Department, Selayang Hospital, Selangor, Malaysia

Introduction
Schwannoma (also known as Neurilemmoma) is a rare, slow growing, encapsulated, benign neural sheath tumor arising from Schwann cells. Their clinical presentation varies; patients may remain asymptomatic or experiencing symptom according to the site of tumor and structures involves. Here we share an interesting rare case of posterior mediastinal schwannoma with mass effect.

Case Report
A 31-year-old active smoker gentleman was referred from a pre-employment health screening to respiratory clinic for assessment. He presented with chronic dull right sided chest and back pain for past three years, associated with occasional right-hand numbness. Physical examination and laboratory investigations were unremarkable. Contrast enhanced CT thorax showed a large right posterolateral mediastinal mass measuring 9.8cmx9.3cmx8.7cm, with mass effect on the esophagus, distal trachea and right bronchus, with erosion to T4 vertebra body.  CT guided biopsy was done and histopathological result was supportive for ancient schwannoma. He was referred to thoracic surgeon and right posterolateral thoracotomy and excision of 10x10cm mediastinal mass was performed. Histopathological result confirmed the mass as Schwannoma, weighing 352 grams, with strong positivity on immunohistochemistry for S100 and SOX10 protein, with low Ki67 proliferative index.

Conclusion
Mediastinal schwannoma is a rare tumor arising from the peripheral nerve sheath of the mediastinum. While schwannomas are usually found in head, neck, flexor surface of extremities and retroperitoneum, incidence of mediastinal schwannomas comprises only 9% of all schwannoma cases. This patient presented with only musculoskeletal chest pain which was atypical. He had no other respiratory symptoms despite radiologically showing large mass affecting important surrounding structures. Surgical excision was done and he recovered well post operatively. Mediastinal schwannomas have great prognosis with no recurrence reported till date.