Intranodal palisaded myofibroblastoma originating from retroperitoneum: an unusual origin

A 72-year old man presented with abdominal pain in right upper quadrant with an incidental finding of abdominal mass in the right flank. The computerised tomogram scan of abdomen confirmed acute cholecystitis with a 5 x 5 cm retroperitoneal mass. He underwent cholecystectomy with excision of this mass. He recovered well following his operation and was discharged from the hospital. Histological examination confirmed the diagnosis of intranodal palisaded myofibroblastoma.To our knowledge, this is the first case of intranodal palisaded myofibroblastoma originating from retroperitoneum. Along with the rarity of this case, we also discussed its typical histopathological findings, aetiology and pathogenesis.In comparison to secondary mesenchymal tumours, primary mesenchymal tumours involving lymph nodes are very rare. The most common primary mesenchymal tumours include Kaposi's sarcoma, pseudosarcomatous malignant melanomas and melanocytic naevi [1]. Intranodal palisaded myofibroblastoma (IPM), one of the rare primary mesenchymal tumours, was first described in English literature in 1968, though not classified as Intranodal palisaded myofibroblastoma [2]. These tumours arise from the lymph nodes and are almost always seen in the inguinal lymph nodes, although few cases of mediastinal and submandibular lymph node origins have also been reported [3]. Its unique microscopic, macroscopic and immunohistochemical features differentiate it from other mesenchymal tumours. IPM shows both myofibroblastic and smooth muscle differentiation with the formation of the "amianthoid fibres". To date only about 55 cases of IPM have been reported in the English literature [4-6]. In this case report we presented another case of IPM, but originating from retroperitoneum. To our knowledge, this origin of IPM has not yet been reported. Apart from the rarity of this tumour, we also discussed its characteristic features, aetiology and pathogenesis.A 72 year-old man presented in the emergency depar