Clinicopathological features, diagnosis and treatment of clear cell sarcoma/melanoma of soft parts.

BACKGROUND Clear cell sarcoma of tendons and aponeuroses is a rare, high grade malignant soft tissue tumor resembling melanoma and soft tissue sarcomas. Clinical and Imaging Presentation: The median age at presentation is 27 years and the most common location are the foot and the ankle. MR imaging typically shows a benign looking, well defined, homogenous mass; on T1-weighted MR images, it is usually homogeneous and isointense or slight hyperintense to muscle, whereas on T2-weighted MR images, it is usually more heterogeneous with variable signal intensity. Pathology: Microscopically, the clear cell appearance is due to the accumulation of glycogen. The cells show no or minimal pleomorphism, and paucity of mitotic figures that is in concordance with the slow-growing behavior of the tumor. Scattered multinucleated giant cells are commonly present; areas of necrosis and melanin pigment may be identified. The reciprocal translocation t(12;22)(q13;q12) is observed in more than 90% of clear cell sarcoma cases. In addition, polysomy of chromosome 8 has been observed as a secondary abnormality in many cases of clear cell sarcoma. The differential diagnosis of clear cell sarcoma should include melanoma, epithelioid malignant peripheral nerve sheath tumor, melanotic schwannoma, paraganglioma-like dermal melanocytic tumor, perivascular epithelioid cell neoplasms (PEComas), cellular blue naevus, synovial sarcoma (monophasic type), alveolar soft part sarcoma, paraganglioma, epithelioid sarcoma and carcinomas. Treatment and Prognosis: The treatment of choice for clear cell sarcoma is wide surgical resection. If complete excision is achieved, adjuvant treatments are not unnecessary. Chemotherapy is predominantly employed in patients with metastatic disease. The 5 to 20 year survival of the patients with clear cell sarcoma range from 67% to 10%. The rates of local recurrence ranges up to 84%, late metastases up to 63%, and metastases at presentation up to 30%.