S3059 Clear Cell Sarcoma of the Jejunum: Dissecting an Obscure Malignancy

Abstract

Introduction: Clear Cell Sarcoma (CCS) of the jejunum is an extremely rare and mortiferous presentation of a poorly understood malignancy. CCS is a cancer of the soft tissue and aponeuroses of tendons, affecting young individuals with predilection towards the ankle. It is often confused for malignant melanoma, as it is also derived from neural crest origin and shares a similar histological appearance. Currently, the only definitive treatment is surgical resection. Even so, CCS is known to recur. Due to the sheer modicum of cases, our medical knowledge is limited. Case Description/Methods: We present a case of a 49-year-old gentleman from Cameroon with a past medical history of hypertension and diabetes mellitus type II, who presented to the emergency department with complaints of abdominal pain, nausea, and vomiting for a one-month duration. CT scan of the abdomen and pelvis revealed left-sided small bowel obstruction. The patient underwent diagnostic laparoscopy, which converted to open surgery, with small bowel resection and umbilical hernia repair. A 2.6 cm circumferential obstructing jejunal mass was identified and resected. The margins of resection were negative for malignancy. There was no lymph vascular invasion, and 12 lymph nodes were negative for malignancy as well. Immunohistochemistry stains resulted positive for S100, SOX 10, and EMA. FISH was positive for EWSR1. Recent studies have revealed a chromosomal translocation, t(12;22) (q13;q12), also known as the EWSR1 and ATF1 gene, respectively, which has been widely accepted as pathognomonic for CCS. At 2 years of follow-up, our patient had a drastic improvement in his symptoms, with active surveillance and close follow-up, as CCS has a high recurrence rate. Discussion: This case report aims to describe the clinical presentation and evolution of this unique soft-tissue malignancy, which can be found in the GI tract in extraordinary cases. We hope this rare case of Clear Cell Sarcoma can enhance our knowledge about this obscure cancer that we still have so much to learn.Figure 1.: This 2.6 cm tumor is present in the submucosa, muscularis propria and subserosa and shows nests and cords of patterns by network of delicate vascular septa. Neoplastic cells are plump with epithelioid, clear cell and focal spindle cell appearance. Mitotic figures are about 5/10HPF. Immunostains show that tumor cells are positive for S100, SOX-10, and EMA but negative for HMB-45, Melan A, carcinoma markers (AE1/AE3, CAM5.2, CK7 and CK20), gastrointestinal stromal tumor markers (CKIT, CD34, and DOG1), lymphoid markers (CD3 and CD20), and desmin and ASMA. EWSR1 is positive by FISH studies. A) (Magnification x40, lower power, hematoxylin-eosin) and B) (Magnification x400, high power, hematoxylin-eosin) show epithelioid and clear cell appearance. C) (Magnification x400, antibody for S100) and D) (Magnification x400, antibody for SOX-10) reveal positivity.