Isolated extra nodal soft tissue Rosai-Dorfman disease, masquerading as soft tissue neoplasm: A rare entity

Abstract

Rosai–Dorfman disease (RDD) is a rare, nonmalignant disorder of histiocyte proliferation which usually involves the cervical lymph nodes. Isolated extranodal RDD is rare which mimics other neoplastic processes thus causing diagnostic difficulties to the clinicians and radiologists. Here we report a case of 32 year old lady who presented with swelling in right thigh, clinically diagnosed as soft tissue neoplasm. Histopathology revealed pathognomonic findings of RDD showing sheets of large pale histiocytes showing emperipolesis along with dense lymphplasmacytic infiltrate. In extranodal RDD the typical histological findings of RDD are less common and there is pronounced fibrosis compared to nodal disease. The pathological diagnosis may be challenging in such cases. The surgical pathologist should have a high index of suspicion in such cases so that aggressive therapy can be avoided. The course of extranodal disease is generally less indolent and can be aggressive if vital organs are involved.