Clear Cell Sarcoma-like Tumor of GI Tract
Clear cell sarcoma-like tumor of the gastrointestinal tract is positive for S-100 protein but generally negative for melanoma markers (HMB-45, Melan A, and MiTF. SOX10 may be expressed. Synaptophysin, NSE, neurofilament, CD56, and CD57 may be positive, creating confusion with neuroendocrine tumors. CD117 (C-kit) and keratins are negative. Ultrastructurally, there are no melanosomes. On the other hand, the cells may show dense-core secretory granules. Molecular Genetics: Majority of the tumors show t(2;22)(q32.3;q12) translocation resulting in EWSR1-CREB1 fusion protein. A smaller subset shows the balanced translocation t(12;22)(q13;q12) resulting in EWSR1-ATF1 fusion protein. The latter translocation is more typical of the clear cell sarcoma of soft tissue. These genetic abnormalities can be detected by RT-PCR or FISH assays. Even though CCS-like tumor of the gastrointestinal tract shares some resemblance with clear cell sarcoma of soft parts, there are enough morphologic, immunohistochemical and genetic differences that some consider it to be a distinct entity. It is a highly aggressive tumor with a tendency to local recurrences as well as distant metastases. Most patients die within 3-yrs. of diagnosis. The image shows a clear cell sarcoma-like tumor of gastrointestinal tract showing a focus of necrosis (upper two-thirds of the image).