Clear Cell Sarcoma: A Clinicopathologic Study And Molecular Cytogenetic Analysis

PurposeThe present study investigates the clinicopathologic characteristics,imaging findings and immunophenotype of clear cell sarcoma(CCS).In advance,we are aiming to evaluate the molecular genetics in the diagnosis and differential diagnosis of CCS.Methods1.92 cases of clear cell sarcoma were retrieved from the files of the Department of Pathology,Cancer Hospital,Fudan University between January 1993 and December 2007 and all the histological slides were reviewed for confirmation of pathologic diagnosis by two professional pathologists.The clinical and histopathologic features were analyzed and patient follow-up were continued.30 cases of malignant melanoma and 30 cases of synovial sarcoma were collected as a control group.2.A panel of antibodies were applied in the immunohistochemical staining of CCS, including S-100,HMB45,A103,PNL2,MITF,Tyrosinase,EMA and AE1/AE3 proteins, to characterize the immunophenotype of CCS.3.RT-PCR was performed to detect the abnormality of the fusion ofEWS-ATF1 gene. Analysis was performed to investigate the value of the fusion gene in diagnosis and differential diagnosis of CCS,as well as the relationship with the clinicalpathologic features.Results1.Clinical characters:(1) Sex:There were 38 male patients and 54 female patients(male to female; 1∶1.4).(2) Age:The age of the patients ranged from 10 to 80 years with the median age of 37 years(average 37.6 years).48.9 percent of patients were aged 20～40 years.(3) Site:The most common tumor site were the limbs,a total of 77 cases(86.5%, 77/89),of which 46 cases occurred in the extremities(51.7%,46/89),33 cases occurred in the foot and ankle,accounting for 37.1%of all cases,12 cases occurred in the uncommon site,including six cases of the trunk,and six cases of the head and neck.The site of three cases remained uncertain.(4) Clinical findings:The vast majority of the cases presented with a local slow-growing tumor or swelling,half of the patients presented with pain or tenderness.The course of the patients ranged from two months to seven years in all 31 cases with follow-up data.(5) Imaging findings:X-ray showed the soft tissue shadow,CT and MRI could clearly show the mass.On T1-weighted images,the lesions exhibited intermediate to low signal intensity,whereas on T2-weighted images,they were high to low signal intensity according to the quantity of the melan pigments. Isotopes and PET-CT scan helped to identify metastases.(6) Treatment:All patients were treated with tumor resection.4 cases of the 31 patients with follow-up data had radiotherapy,11 had chemotherapy,6 had both chemotherapy and radiotherapy in the treatment and 10 patients didn't have any aftertreatment;(7) Prognosis:A follow-up data of 31 patients with clear cell sarcoma showed that nine cases had recurrence with a time of a month to 5 years(average,33.8 months),11 cases had lymph nodes or lung metastases,5 patients died of the tumor,the survival time from 4 months to 5 years,with an average of 18 months after the operation.2.Pathologic findings:(1) Gross findings:All except three were described as a solitary firm mass,with a nodular or lobulated appearance.The tumor measured from 1.0 to 7.0 cm in diameter(average,3.2 cm) with grayish color on cut surfaces.Hemorrhage, necrosis or cystic changes were seen in some cases,and the pigmentation was seen in 20%of the cases.(2) Histological findings:The tumors were composed of uniform round,ovoid or polygonal cells arranged in nests or fascicles that separated by thin fibrous septa.On light magnification,the tumor cells contained clear,pale to eosinophilic cytoplasm and round to ovoid nuclei with prominent nucleoli. Multinucleated giant cells were noted in about 40%cases.Intracytoplasmic melan pigments were noted in 20%cases.Myxoid change was seen in a few cases.The mitotic figures ranged from 0/10HPF to 5/10HPF(mean,1/10HPF).3.Immunohistochemical findings: S-100 protein(39/40,97.5%),HMB-45(37/42,88.1%),A103(11/23,47.8%), PNL2(21/25,84.0%),MITF(6/11,54.5%),Tyrosinase(6/14,42.9%),EMA (3/23,13%),AE1/AE3(2/23,8.7%)。4.Molecular genetics:The fusion transcripts of EWS-ATF1,derived from t(12;22)(q 13;q 12),were detected by RT-PCR in 29 cases of CCS with available paraffin blocks.The value of molecular assay in the diagnosis and differential diagnosis of CCS was evaluated.The relationship between fusion variants and the clinicopathological representations was also discussed.12 of 23 cases showed the fusion transcript. Subsequent analysis of the PCR product revealed that 11 cases of which represented type 1 EWS-ATF1 fusion transcript consisting of an in-frame fusion between EWS exon 8 and ATF1 exon 4 and 4 cases represented type 3 fusion transcript.Type 2 fusion transcript was not found.No fusion transcript was found in the cases of control group.5.Control group:(1) In 30 cases of malignant melanoma,there were 18 male patients and 12 female patients(male to female;1∶1.5).The age of the patients ranged from 30 to 80 years with the median age of 63.5 years(average,61.3 years).19 cases occurred in the limbs and 11 cases occurred in the other sites,including six cases of the viscus,two cases of the nasal cavity,one case of parotid,one case of cheek and one case of the lymph node metastasis.Immunohistochemically,S-100 protein(29/30,96.7%),HMB-45(29/30,96.7%),A103(24/26,92.3%), PNL2(25/26,86.2%),MITF(10/16,62.5%),Tyrosinase(6/12,50%),EMA (0/30,0%),AE1/AE3(0/30,0%).The EWS-ATF1 fusion transcript was not found by RT-PCR.(2) In 30 cases of synovial sarcoma,there were 15 male patients and 15 female patients(male to female;1∶1).The age of the patients ranged from 12 to 64 years with the median age of 33 years(average,35.6 years).20 cases occurred in the limbs and 10 cases occurred in the other position,including two cases of head and neck,four cases of thorax,two cases of abdomen and two cases of abdominal wall.Immunohistochemically,S-100 protein(9/30,30%),HMB-45 (0/20,0%),EMA(21/25,84%),AE1/AE3(24/27,88.9%).The EWS-ATF1 fusion transcript was not found by RT-PCR. Conclusions1.Clear cell sarcoma is a rare soft tissue tumor mainly occurs in young and middle-aged adults with a female predilection.2.The most common site was the extremity,and the foot and ankle were by far the most common single location of the tumor,followed by the thigh,hand and forearm and the knee,a small number of cases may occur in the head and neck,trunk and other positions. The vast majority of cases showed a locally slow-growing tumor or swelling.Tumors were often found in the deeper position attaching to the tendon or aponeurosis,without skin adhesion.3.X-ray often showed the soft tissue shadow and CT and MRI examination could clearly show that mass.Isotopes and PET-CT could find metastasis.4.Histologically,the tumor cells contained clear,pale to eosinophilic cytoplasm and round to ovoid nuclei with prominent nucleoli.Multinucleated giant cells were noted in about 40%cases.Intracytoplasmic melan pigments were noted in 20%cases.The mitotic figure was scarce.5.Immunohistochemically,similar as malignant melanoma,the tumor cells of clear cell sarcoma had been detected expressed S-100 protein,HMB-45,A103 and PNL2.6.Clear cell sarcoma is now characterised cytogenetically and molecularly by a characteristic chromosomal translocation,t(12;22)(q13;q12),which leads to the fusion of EWS-ATF1 gene.The detection of the gene mutations will be useful in correct diagnosis of CCS.7.The fusion transcript does not affect the clinicopathological representations of clear cell sarcoma.