Clear Cell Sarcoma

Introduction: Clear sell sarcoma is a very rare type of sarcoma. The diagnosis of this subtype of sarcoma is very challenging. Case report: Male 45 years old. He presented with a non typical skin lesion in the area of left heel in Sep 2019. Initially some focal treatment maybe with ablation or a kind of laser took place by a dermatologist without any improvement. Afterwards, in Oct 2019 a biopsy from that lesion took place and the pathology examination revealed a neoplasm without necrosis, number of mitoses around 3-4 and Ki-67 around 10%. The more possible diagnosis was clear cell sarcoma or malignant melanoma. Further molecular diagnosis in Nov 2019 confirms the diagnosis of clear cell sarcoma with the presence of EWSR1 in approximately 50% of tumors cells (typical 49% and not typical 29%). Moreover, BRAF mutation analysis was negative. Therefore, a proper surgical approach by our plastic surgeons took place in Dec 2019. In particular excision of left calcaneum with sentinel lymph node took place. Pathology examination revealed a neoplasm of 1.3cm max diameter with clear cell sarcoma characteristics. Regarding surgical margins tumor the nearest was 2.2mm. There were multiple small metastatic lesions-infiltrations in the sentinel lymph node the largest one was >2.5mm (without any exocapsic infiltrations). Moreover, in sentinel lymph node some neoplasmatic emboli in veins were found (vascular invasion). Regarding TNM stage it was evaluated as pT1N1Mx by the pathology report. Further and extensive work up with clinical and radiological examinations took place (CT scans, MRIs, Bone-scan and PET-Scan) and was negative for any distant metastases. Additional, due to the close surgical margins a second surgical excision in left heel took place but fortunately the histology examination of new tissue biopsies was negative for any remaining neoplasm or any tumor infiltration. In summary, this gentleman is diagnosed with a Clear Cell Sarcoma of left calcaneum EWSR1 positive that was resected. It is stage IV (T1N1M0) probably G3, without necrosis, number of mitoses around 3-4 and Ki-67 10%, with some vascular invasion and questionable surgical margins in some areas of surgical excision (second surgical excision took place that was negative for any remaining tumor). Conclusion: Clear Cell Sarcoma is a very uncommon type of sarcomas that should be differentiated from melanoma. The diagnosis sometimes is very difficult and challenging. Molecular diagnosis is recommended.