 Good morning, I am Dr. Anurag Jaiswal, PG resident in TS Misra Medical College and Hospital Lucknow, Uttar Pradesh. I am presenting a rare case report of benign multi-cystic peritoneal mesotheloma in young male individual. For case description, a young wife presented with two-year history of gradual progressive abdominal swelling and fullness. They have the intermittent abdominal pain for the past two months. Apart from these symptoms, there were no other notable complaints. No previous medical history of illness. The proceeding with the imaging, the first imaging we did the X-ray abdomen and trapezius. Grosally, the X-ray abdomen appears normal. There is no gas in the diaphragm so we ruled out the nemoperitoneum. No sign of obstruction because there is no air fluid level is seen in the visualized bowel. But definitely there is some mass seen in the right side of the abdomen which caused the displacement of the bowel loops towards the periphery or towards the left side. We did the ultrasonography of the abdomen and we found a large cystic legion which extends from the right side of the diaphragm to the right pelvis. It measures approximately 16-17 x 13 cm. It is very large, occupying almost all of the abdomen. This cystic legion contains multiple thin septa which does not show any vascularity on color doppel. The cyst having the low level internal echos. There is no abnormal calcification is seen. There is no mural nodule is appreciated. The next image of ultrasonography which shows the multiple thin septa and this is the very large cystic legion. The liver appears normal in size and ecotextile and the right kidney shows hydroerotonephrosis because this cyst causes the mass legion or causes the compression of the right proximal erector causing upstream hydroerotonephrosis. The spline is normal in size and ecotextile. The left kidney is normal in size with maintained CMD and no pelvic helical system dilatation. Apart from these visceral organs we are not able to appreciate the pancreas or the bowel because this cystic mass almost occupying whole of the abdomen. So, the ultrason examination revealed a large multi cystic legion with multiple thin septa and low level internal echos extending from the mid abdomen to the pelvis which causes the mass effect on the right proximal erector leading to dilatation of the pelvic helical system of the right kidney. We advise for the CT abdomen for better depiction of this cystic or the complex cystic legion. This is the CT abdomen, the axial section we can see there is a large cyst which occupying whole of the abdomen with the thin septa. This is the mass effect on the right side of the erector, proximal erector causing the hydroerotonephrosis of the right kidney. This is the coronal section which shows the extension of the cyst from the right side of the diaphragm to the right side of the pelvis. Even we can appreciate there is a mass effect on the bladder, on the urinary bladder. The coronal and the sagittal section which shows a clear hydroerotonephrosis of the right kidney due to the mass effect of this multi cystic legion. So this is the contrast enhancer study which shows the mild enhancement of septa and better depiction of the right side of the hydroerotonephrosis. Again the coronal section through the hydroerotonephrosis apart from this mass effect on the right proximal erector there is also the mass effect on the major abdominal vessels. The abdominal aorta is displaced to the left side also there is a mass effect on the abutment of the right side of the common ilogatory. So CCD abdomen revealed a well-defined, lobulated, thin-walled intraperitoneal complex cystic lesion which have the averis honspin unit of plus 14. The lesion had multiple, mildly enhancing septa and involved most of the abdomen and pelvis on the right side extending from the infrihipatic region to the right iloghosa. There was also extension to the left side the complex lesion exerted mass effect on adjacent intraperitoneal organs displacing a small bobble loops medially. Most early it aborted and compressed the right upper erector was in moderate upstream hydroerotonephrosis. Additionally it aborted and displaced the abdomen aorta, right common ilogatory and compressed the inferior vinaigrette. Superiorly it displaced the right kidney while inferiorly it aborted and compressed the superior lateral surface of the right urinary bladder. There were no obvious signs of neural nodulity or enhancing shock tissue within the lesion. So the differential diagnosis they are considered was the cystic lymphangioma, chiral lymphatic midgintrix cyst and multi-cystic peritoneal mesothereoma. The patient was referred for surgical excision of the mask to obtain a tissue sample for histopathological examination which would provide a definite diagnosis. The patient underweight laparotomy during which the multi-cystic mass was excised. Additionally an appendectomy was performed upon exploration. It was discovered that the multi-cystic mass occupied the entire abdomen and was added into the small bobble. The tumor was dissected except in areas where it was inseparable from surrounding organs and tissues. The patient experienced an uneventful postoperative recovery and did not encounter any complications. The histopathological examination grossly it the excise specimen appeared as a globular grey-brown soft tissue mass. Upon cutting the mass multiple localitis cysts with variable wall thickness were observed. The cyst content zeroes to grey-brown fluid. Microscopic sections showed that the cystic lesion were aligned by flattened cells and walls exhibited variable thickening characterised by fibroblastic tissue with collagen deposition. No granulomas or malignancies were observed. These histopathological features were suggested to go of benign multi-cystic peritonal mesothelium. Immunomist chocomastric testing advice including CK56, CK7, calratine, WT1 and CD31 to further supported diagnosis. This is the microscopic section shows the cystic lesion aligned by flattened cells with variable thickened walls characterised by fibroblastic tissue with collagen deposition. Two words about the malign multi-cystic peritonal mesothelium. It is a very rare condition primarily seen in middle-aged women during their reproductive age with an extremely low annual incidence of 0.15 per lac cases. Predisposing factors include chronic inflammation, previous surgeries, endometriosis and peritonealitis linked to peritoneal dialysis. Till date, less than 200 cases have been reported in the literature making diagnosis challenging. We talk about reported cases in India, it is still less than 20 cases. The prognosis of BMPM is not definitely stabilised due to its rarity however based on the limited reported cases the prognosis seems generally favourable. It is a rare tumor originating from mesothelial tissue characterised by peritoneal cyst from both epithelial and mesocannol component. It is a minimal risk of becoming malignant at its disease not linked to asbestos exposure. BMPM commonly manifests in pelvic lesion but can also appear in other areas like the kidneys, bladder, lymph nodes, liver and spleen. In early stages it is asymptomatic or show minimal symptoms however as it grows and puts pressure on nearby organs symptoms become more noticeable. These symptoms are generally non-specific and may involve abnormal pain, palpable masses and constipation. On ultrasound appears as multi-static aneuquatic lesion filled with fluid. CT scan is used to assess its location extent. MRI is the preferred technique showing BMPM as hypointense lesion on T1 weighted images and hypoterointermediate intense lesion with mild wall enhancement on T2 weighted images. Thank you.