Clear cell sarcoma

Clear Cell Sarcoma

Micrograph of clear cell sarcoma showing characteristic features.

Clear cell sarcoma is a rare type of soft tissue sarcoma that is often associated with tendons and aponeuroses. It is sometimes referred to as "malignant melanoma of soft parts" due to its histological and immunohistochemical similarities to melanoma.

Pathophysiology

Clear cell sarcoma is characterized by the presence of clear cells, which are so named because of their pale, clear cytoplasm when viewed under a microscope. This appearance is due to the presence of glycogen within the cells. The tumor cells typically form nests and are surrounded by fibrous septa.

A defining feature of clear cell sarcoma is the presence of a specific chromosomal translocation, t(12;22)(q13;q12), which results in the fusion of the EWSR1 gene on chromosome 22 with the ATF1 gene on chromosome 12. This genetic alteration is a key diagnostic marker and plays a role in the pathogenesis of the disease.

Clinical Presentation

Patients with clear cell sarcoma often present with a slow-growing mass that is typically located in the extremities, particularly the lower limbs. The tumor is usually deep-seated and may be associated with pain or tenderness. Due to its indolent nature, the diagnosis is often delayed.

Diagnosis

The diagnosis of clear cell sarcoma is based on a combination of clinical, radiological, and histopathological findings. Imaging studies such as MRI and CT scan are used to assess the extent of the tumor. A biopsy is necessary to obtain tissue for histological examination.

Histologically, clear cell sarcoma is composed of nests of uniform, round to oval cells with clear cytoplasm and prominent nucleoli. Immunohistochemical staining is positive for markers such as S-100 protein, HMB-45, and Melan-A, which are also seen in melanoma.

Treatment

The primary treatment for clear cell sarcoma is surgical resection with wide margins to ensure complete removal of the tumor. Due to the high risk of local recurrence and metastasis, adjuvant therapies such as radiation therapy and chemotherapy may be considered, although their effectiveness is limited.

Prognosis

Clear cell sarcoma has a poor prognosis due to its aggressive nature and tendency to metastasize, particularly to the lungs and regional lymph nodes. The 5-year survival rate is approximately 50%, and long-term follow-up is necessary to monitor for recurrence and metastasis.

Related Pages

• Soft tissue sarcoma
• Melanoma
• EWSR1
• ATF1