PDP INSIGHTS

Excerpt

The most common malignant tumor of the soft tissues in children is rhabdomyosarcoma (RMS), and as such, pediatric pathologists are in general well acquainted with the many variants of this neoplasm. However, RMS also affects, although rarely, the adult population, and a reported phenotypic variety of this tumor appearing in older patients prompted a review of the Intergroup Rhabdomyosarcoma Study Group and Children’s Oncology Group files to identify possible pediatric examples with this morphologic variation. This work (pages 583–594, DOI: 10.1007/s10024-004-5058-x) confirms previous observations published by Bale and Reye in 1975, and more recently by Zambrano et al. (Lab Invest 2004; 82:277), and also a recently reported example of this form of RMS published in our Journal (Pediatr Dev Pathol 2004 7:391–396) by Vagdama et al. The sclerosing variant of RMS is now a well-established phenotypic variant that may escape diagnosis by virtue of its abundant hyalinizing matrix that mimics osteosarcoma or chondrosarcoma, or because of the presence of carcinomatoid and pseudovascular patterns. In total, 17 patients appear to be on record in the recent literature (thirteen of these patients are included in the current report), in addition to the 5 juvenile patients described by Bale and Reye almost 30 years ago. Other unusual features of sclerosing RMSs include a weaker staining with myogenin, and predominantly negative gene-fusion results, which casts doubts of their inclusion within the alveolar group, as it has been suggested. Based on these observations, we need to be aware of tumors that may mimic osteosarcoma and/or other more rare forms of malignancy in the soft tissues of children. Undoubtedly, additional genetic, clinical and morphological information will become available as investigators acquire more familiarity with this group of tumors. …