Cytogenetic abnormalities of alveolar soft-part sarcomas using interphase fluorescent in situ hybridization : trisomy for chromosome 7 and monosomy for chromosomes 8 and 18 seem to be characteristic of the tumor

Four alveolar soft-part sarcomas were investigated by means of standard immunohistochemistry and interphase cytogenetics to further characterize the immunophenotype and proliferative activity of this tumor. The main goal of this study was to explore the chromosomal changes of this rare soft-tissue sarcoma. One epithelial (KLI), three neurogenic [neuron specific enolase (NSE), PGP 9.5, and S100], and five myogenic (desmin, myoglobin, alpha-smooth mnuscle actin, alpha-sarcomeric actin, and MyoD1) markers were used for the immunophenotypical analysis. Proliferative activity was assessed using the Ki67 index. Twelve (peri)centromeric (1, 3, 4, 6, 7, 8, 10, 12, 15, 17, 18, and X) and one telomeric (17q25-qtel.) chromosomal probes were used for interphase cytogenetic analysis. Three of the cases showed cytoplasmic desmin and/or myoglobin, and one showed smooth muscle actin positivity. All of the four tumors had granular, cytoplasmic, possibly nonspecific MyoD1 and sarcomeric actin positivity. Two of the tumors were positive for vimentin, four gave focal and weak staining with neurogenic markers (four of four NSE, one of four S100, and four of four PGP 9.5), but none of them was positive with KLI. Alveolar soft-part sarcomas may show myogenic immunophenotype in a number of cases, which supports myogenic differentiation. Fluorescent in situ hybridization using alpha satellite chromosomal probes revealed significant alterations in all of the cases. Most frequent and repeated numerical changes, which seem to be characteristic of the neoplasm and may play an important part in its pathogenesis and/or progression, were trisomy 7, monosomy 8 and monosomy 18.