Rhabdomyosarcomas: structural distribution and analysis of an immunohistochemical profile

Abstract

To qualitatively and quantitatively assess the expression of myogenic transcription factors on a large sample, to identify potential phenotypic differences, and to estimate the distribution and frequency of aberrant markers, such as ALK, PAX5, WT1, PCK, CAM5.2, SIX1, and Synaptophysin. The investigation included 202 tumor tissue samples. Five tissue microarrays were assembled from the obtained material for subsequent histological and immunohistochemical studies. Embryonal RMS (ERMS) was diagnosed in 103 cases; alveolar RMS (ARMS) was detected in 80; spindle-cell/sclerosing RMS (SRMS) was found in 16 cases; epithelioid RMS (EpiRMS) was diagnosed in 2 patients. The expression of Myogenin and MyoD1 was detected in all the examined RMS tissue samples. ARMS was more characterized by staining at 1+ and 2+ intensities; at the same time, more than 50% of ERMS, SRMS, and EpiRMS cases showed staining at 1+ intensity. ALK expression was investigated using the D5F3 and p80 clones. The D5F3 clone displayed a higher staining intensity than the p80 clone (p<0.05). The expression of PAX5 was observed in 13 of 75 ARMS cases. That of WT1 and SIX1 was found in all RMS groups. The morphological diagnosis of RMS requires a careful assessment of all of the above factors, especially taking into account the variability in the expression of myogenic transcription factors and the high level of phenotypic aberration.