Soft tissue Sarcomas: Immunohistochemistryevaluation by Desmin, Myosin, Smooth muscle Actin and Vimentin


Background:Soft tissue sarcomas (STS) are relatively rare tumors, representingless than 1% of adult malignancies based on report from American Cancer Society. The crude incidence rate in Iraq for soft tissue sarcomas was 219/ 100,000 populationsduring 2014 with a male: female ratio of 1.2:1, and the highest age peak falling between 30-34 years.The histological subtype and microscopic criteria are two parameters that influence the tumor grade which is the best predictor for aggressiveness.Objectives:A retrospective evaluation of soft tissue sarcomas, using immunohistochemical (IHC) study of Myosin, Desmin, Smooth muscle Actin (SMA) and Vimentin, aiming to reviewthe primary diagnosis and whether IHC assessment in soft tissue sarcoma is mandatory to reach a final interpretation.Patientsand methods:A total of 50 cases of soft tissue sarcomas were reviewedretrospectively from case archives of histopathology department/ Central Public Health LaboratoryandGhazi Al Hariri Hospital for Specialized Surgeries for the period (2011-2018). Hematoxylinand Eosin (H&E) stain and IHC staining of unstained sectionsfrom formalin-fixed, paraffin-embedded tissuewereperformed using SMA, Vimentin, Desmin and Myosin.The staining intensity was assessed based on the percentage of positive cell expression of the four IHC monoclonal antibodies.Results:The staining interpretation of the four monoclonal antibodies were confirmatory for the original diagnosisin 40% of cases,while 60% of the final diagnoses werere-evaluated and a different interpretation was givensupported bythe IHC findings for Desmin, Myosin, SMAand vimentin, under the clinical and radiological context.Conclusions: The co-expression of SMA and Desminhelped in the diagnosis of leiomyosarcoma (LMS).Myosin expression was helpful in the diagnosis of rhabdomyosarcoma (RMS)and alveolar soft part sarcoma(ASPS).SMAand Vimentinwere not specific for the diagnosis of malignant fibrous histiocytoma (MFH). By applying IHC markers, 60% of soft tissue sarcomas were found to be different from the preliminary diagnosiswhile 40% of cases were supportive of the original H&E diagnosis