 Hello everyone, I am Dr Chandrika Mukherjee resident in MMI MSR, Malana. I am here to present a paper on malignant peripheral nerve sheet tumors. So, here I start with case presentation. A 54-year-old male was admitted to our hospital with left chest wall mass. Patient had complaints of pain on left side of chest with difficulty in breathing. On examination, a well-defined smooth firm mass of approximately 4 x 3 cm was palpable on left side of chest. Patient was then planned for CECT chest followed by biopsy from the lesion. Non-contrast CT images revealed heterogeneously soft tissue density lesion in left pleural cavity posteriorly in lower chest wall which was seen a butting coastal and diaphragmatic pleura. On post-contrast images, the similar lesion showed minimal enhancement and was seen a butting esophagus medially and parietal pleura laterally with no obvious invasion in the chest wall and the fat planes with esophagus were also maintained. There was associated collapse of left lower lobe of lung and few nodules were also seen in costophrenic and cardiophrenic recesses. On PET CT, the similar mass revealed increased FDG uptake and on biopsy, the microscopic sections showed spindle cell neoplasm consistent with malignant peripheral nerve sheet tumors and on IHC typing of the tissue, it was negative for CD34, chalretinin, S100, SMA, EMA and P63. Patient was then started with chemotherapy with eifosfamide and edryomycine. Let's have a brief discussion on MP-NSTs. MP-NSTs are malignant tumors arising from the sheets of peripheral nerve fibres derived from Schwann cells. These are rare, accounting for only 5-10% of all soft tissue sarcomas. The origin of these tumors is sporadic, which is seen in 40-50 years age group and also in neurofibromatosis type 1 patients. In these patients, the origin can be at an early age that is from 28 to 36 years. Men and women are equally affected. The main pathogenesis of MP-NSTs lies in mutations, which can be seen in patients with NF1. NF1 gene is responsible for production of neurofibromin. Neurofibromin is a negative regulator of RAS-MPK. The mutation in this gene causes pause in the negative regulator which further promotes cell proliferation and leading to MP-NSTs. Other mutations can also be seen in CD-NK2A gene, TP53 and PRC2. This tumor shows rapid increase in size with progressive neurological deficit or pain. Pain is particularly pointed towards the suspected malignant degeneration. During physical examination, special attention should be given to examining for the presence of cafeoulaid spots, auxiliary freckling, inguinal freckling and leash nodules for neurofibromatosis. On CD, these tumors are usually lower tenuating and mildly enhancing. Large elongated or void masses occurring along a nerve with compression or destruction of adjacent structures and pleural abnormalities indicated malignancy. On MRI, similar lesions are isointents on T1 weighted images, hyperintents on T2, with a fusiform shape showing tapered ends that is longitudinally oriented in distribution of peripheral nerve. The characteristic features of MP-NSTs are large size, necrosis, hemorrhage, heterogeneous enhancement and invasive margins. The differentials of MP-NSTs include empyma, which can be differentiated as empyma are non-enhancing. Patient presents with fever, has raised TLC count and on aspiration, pus is seen. Other differentials include benign peripheral nerve sheet tumors, which are slow growing as compared to MP-NSTs. Plural-based tumors, lung masses, consolidation, sarcoma are the other differentials. On histology, MP-NSTs are composed of spindle cells arranged in vesicular, peritheliometers and story form pattern. They have marked nuclear pleomorphism vesicular chromatin in conspicuous nucleoli, mitotic figures and pale less cytoplasm. They may show lack of expression of S-100 because of de-differentiation and occasionally gaping blood vessels, myxoid areas and necrosis may also be seen. The mainstay of the treatment is surgery with neo-adjuvant chemo radiotherapy and studies and trials have revealed doxorubicin plus i-phosphamide has offered best progression free survival. However, sadly, prognosis of this tumor is poor and reoccurrence is high. Thank you so much.