Indian Journal of Pathology and Oncology 2019;6(4):671–676 Content available at: iponlinejournal.com Indian Journal of Pathology and Oncology Journal homepage: www.innovativepublication.com Original Research Article Rare tumors of retroperitoneum-A diagnostic challenge Ranuva Vaishnavi 1 , Bandavat Sankar Naik 1 , P Premalatha 1 , Ch Ramya 1 , I V Renuka 1, * 1 Dept. of Pathology, NRI Medical College, Chinnakakani, Andhra Pradesh, India ARTICLE INFO Article history: Received 21-02-2019 Accepted 02-05-2019 Available online 22-11-2019 Keywords: Retroperitoneum Sarcoma Immunohistochemistry Epithelial Mesenchymal Rare tumors ABSTRACT Introduction: Retroperitoneum can show a wide spectrum of diseases, including a variety of rare benign and malignant neoplasms that can be either primary or metastatic. Most retroperitoneal tumors are malignant, and soft tissue sarcomas account for one third of the cases. The most common sarcomas occurring in the retroperitoneum are Liposarcomas, Malignant Fibrous Histiocytomas, and Leiomyosarcomas. Subtyping of these tumors is important for the different targeted therapeutic options available. Aims and Objectives: To study the distribution of benign and malignant retroperitoneal tumors. Materials and Methods: Study design – Prospective study done in the department of Pathology from January 2013 to December 2017. Immunohistochemistry (IHC) was done wherever necessary. Results: A total of 62 retroperitoneal tumours were studied of which 19 were benign & 43 were malignant. Rare benign tumors encountered were Adrenal Myelolipoma, Benign Fibrous Histiocytoma, Fibrolipomatous Hamartoma and multiple Paragangliomas. Rare malignant tumors were adult onset Wilms’ tumor, De-differentiated Liposarcoma, Epithelioid GIST, malignant GIST of the mesentery and Carcinosarcoma of Kidney. Conclusion: Amongst the retroperitoneal tumors received, malignant tumors were higher in distribution than benign tumors. The commonest epithelial tumor being Renal Cell Carcinoma and mesenchymal tumor being Liposarcoma. The study of rare malignant tumors was done with the help of IHC markers. © 2019 Published by Innovative Publication. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by/4.0/) 1. Introduction Primary retroperitoneal neoplasms are rare comprising 0.1- 0.2% of all malignancies. 1 In retroperitoneum malignant tumours are more frequent than benign lesions but elsewhere in the body benign diseases predominate. Soft tissue (mesenchymal) tumours of retroperitoneum are less common, but constitute 15% of all primary sarcomas. 2 Retroperitoneal tumours can cause a diagnostic dilemma and present several therapeutic challenges because of their rarity, relative late presentation and anatomical location often in close relationship with several vital structures in the retroperitoneal space. 3 We aim to study the distribution of both benign & malignant tumors of the retroperitoneum with emphasis on the clinicopathological picture of the rare * Corresponding author. E-mail address: repriya56@gmail.com (I. V. Renuka). tumors we encountered. 2. Materials and Methods Biopsies of 62 retroperitoneal tumors from patients who were admitted to the hospital from January 2013 to December 2017 were studied. Complete clinical details including radiographic findings were procured. All specimens were fixed in 10% Formalin and then subjected to macroscopic examination. Representative samples were taken, processed and stained with routine Hematoxylin & Eosin stains. Special stains and IHC were used where ever necessary. https://doi.org/10.18231/j.ijpo.2019.127 2394-6784/© 2019 Innovative Publication, All rights reserved. 671