# A Rare Case of Extranodal Rosai-Dorfman Disease Involving the Entire Colon

## TL;DR

A rare case of a non-cancerous histiocytic disease affecting the entire colon in a 47-year-old man is reported and successfully treated.

## Contribution

This paper presents a rare extra-nodal variant of Rosai-Dorfman Disease involving the entire colon in an adult patient.

## Key findings

- RDD was diagnosed in a 47-year-old male with chronic abdominal symptoms and colon involvement confirmed via imaging and histology.
- The patient underwent total abdominal colectomy and has remained in remission for four years.
- Histopathological analysis confirmed extra-nodal RDD with transmural involvement of the colon and mesentery.

## Abstract

Previously known as sinus histiocytosis accompanied by massive lymphadenopathy, Rosai-Dorfman Disease (RDD) is an extremely uncommon idiopathic histiocytic condition that does not have a malignant cause. In young patients, RDD often manifests as a painless cervical lymphadenopathy. However, some cases present as the extra-nodal variant of the disease, which might show a mass in the skin, soft tissue, nasal cavity, eye, bone, or other sites. RDD's involvement in the gastrointestinal (GI) tract is exceedingly uncommon. We reported a case of extra-nodal RDD affecting the GI tract in a 47-year-old Indian male patient who presented with chronic lower abdominal pain and constipation. On computed tomography, there was circumferential thickening of the ascending, transverse, and descending colon and recto-sigmoid junction with luminal narrowing and pericolic enlarged lymph nodes. Similar short segment lesions were noted in the duodenum without luminal narrowing. Colonoscopy showed luminal narrowing at the sigmoid colon with inflammatory changes of the mucosa. After receiving treatment at different centres for almost a year, the patient underwent total abdominal colectomy with ileorectal anastomosis and was diagnosed with RDD, extra-nodal type. Microscopy showed histiocytic disease with transmural involvement of the entire colon and surrounding mesentery. The histiocytes were negative for c-kit but positive for S100 and CD68. Related literature was reviewed and compared with this case. The patient is regularly followed up in the outpatient department and is under remission for four years of follow-up.