ALVEOLAR SOFT PART SARCOMA: AN IMMUNOHISTOCHEMICAL AND FLOW-CYTOMETRIC STUDY

The aim of this study is to investigate the nature, the tissue type and ploidy pattern of alveolar soft part sarcoma (ASPS) which is rare tumor of uncertain origin. Four cases of ASPS were obtained from pathology files. The tumors were stained with PAS-Diastase, PAS, Grimellius, Masson-Fontana and were analysed immunohistochemically for Neurofilament, S-100 protein, Desmin, Smooth Muscle Actin, Neuron Specific Enolase (NSE), Chromagranin, Synaptophysin, Cytokeratin. Flow cytometric analysis was performed using Becton-Dickenson Facscan Flow Cytometer One case of paraganglioma was used for comparison. All ASPS's were characterised by increased nuclear hyperchromatism pleomorphism and distinct nesting pattern. PAS for diagnosis of ASPS, revealed characteristically PAS positive, diastase resistant rhombdoid or rod-shaped crystals. Except for weak Desmin Smooth Muscle Actin (SMA) in two cases and focally weak NSE and S-100 positivity in one case, no immunoreactivity was detected. In flow cytometric study, all were aneuploid. DNA index ranged between 1,14-1,23. The average of the S-Phase fraction was 30,5% (15-42%). Paraganglioma showed both ploidy and aneuploidy changing from one area to other. ASPS is an uncommon but distinct soft tissue sarcoma. PAS staining still remains the efficient method in differential diagnosis. Weak desmin positivity may suggest myoid origin. Without the application of other nueroendocrine markers, NSE positivity may lead to misinterpretation towards paraganglioma diagnosis due to it's morphological resemblance. But flow cytometric analysis could not be used to differantiate ASPS from paraganglioma for the 4 cases studied.