Background: The incidence of MPNST is 0.001% in the general population. Although MPNST can be found in any part of the body including extremities, head and neck, trunk, or retroperitoneum, intrathoracic MPNST with or without NF1 is uncommon, only with several reported adult cases. We report a very rare case of MPNST presenting as an middle mediastinal mass treated by surgical excision.
Case presentation: A 29 year old non smoker woman with no previous history of pulmonary tuberculosis complained of difficulty of breathing that started one month prior to admission. On examination, she was not in respiratory distress, occasional fine crackles on lower lung fields were noted during chest and lung examination. Chest radiograph showed a convex soft tissue density in the right hilum, consider a mediastinal mass. This was confirmed via chest CT scan which revealedthe presence of a 7 x 6 cm heterogenous mass located in the middle mediastinum with massive pericardial effusion and minimal pleural effusion. Excision of the mass was done revealing a 6 x 5 cm middle mediastinal mass extending from the anterior surface of the superior vena case insinuating between the medial aspect of the SVC at the aorta. Biopsy revealed a malignant peripheral nerve sheath tumor with focal muscle differentiation.
Discussion: MPNST is also known as malignant schwannoma, neurofibrosarcoma and neurogenic sarcoma. More than 50% patients with MPNST have NF1 with a reported five year survival of 15%. Histopathological examination remains the mainstay to arrive at the diagnosis of the malignant nature of schwannoma. In our patient, the MPNST was identified in the middle mediastinum extending from the superior vena cava, based on case reports that have been previously documented this tumor could have been originated from the vagus nerve.
Conclusion: MPNST is considered as one of the most important neurogenic tumor. Our patient presented with a MPNST in the middle mediastinum which is considered as a rarefied case. The possibility of nerve sheath tumor should be taken into consideration even if it is not manifest in the posterior mediastinum