A Case of Extra-nodal Rosai-Dorfman Disease.

Rosai-Dorfman disease (RDD) doesn't cause major health issues for most people. That said, it can present in many different ways and often resembles more serious conditions, including certain types of cancer. Because RDD is so rare, it is often overlooked, partly due to the absence of clinical algorithms for classifying its subtypes and guiding management. Thus, it is significant to consider advancements in the various clinical manifestations of RDD, which can effectively guide concise clinical management. This case report will discuss a 50-year-old female who had a soft tissue mass for over 15 years, which recently began to enlarge exponentially over the course of a few months. CT imaging revealed a cutaneous mass on the left flank. The initial diagnosis was leaning towards a lipoma. However, a core needle biopsy was performed and examined histopathologically to rule out malignancy. The findings of the biopsy confirmed the diagnosis of extra-nodal cutaneous RDD by using specific immunohistochemistry markers. The patient underwent a wide, local surgical excision, with resolution of symptoms. This case shows an unusual form of RDD that appears outside the lymph nodes, specifically in the skin's soft tissues. Though skin manifestations can be seen in extra-nodal RDD, the majority of RDD is confined to the lymph nodes. This case presents an opportunity to expand knowledge of a rare benign disease that presents with diverse clinical manifestations that can mimic a lipoma or malignancy (lymphoma), enabling clinicians to accurately diagnose and differentiate it from malignancies that may have similar presentations.