Osteosarcoma - Transmission Electron Microscopy and Molecular Biology and Diagnostics Update

Pediatric small round blue cell tumors are a vast category of tumors occurring in infancy and childhood. Light microscopy of small round blue cell tumors reveals round cells. They usually have a hyperchromatic nucleus and relatively sparse basophilic cytoplasm. Pediatric small round blue cell tumors encompass various entities, including nephroblastoma (Wilms’ tumor), neuroblastoma, rhabdomyosarcoma, Ewing sarcoma, retinoblastoma, and malignant lymphoma. These tumors represent the most prevalent diagnoses of solid malignancies in pediatric and adolescent populations. The differential diagnosis of these neoplasms can be intricate or contentious at the light microscopic level, even with immunohistochemistry. Occasionally, subtle staining or an unclear background may impede pathologists’ ability to reach an accurate diagnostic conclusion. Molecular biology can generate large volumes of data that are difficult to distinguish. Consequently, electron microscopy can be beneficial for accurately validating the findings from light microscopy. Moreover, the ultrastructural state can provide insights into findings that may be relevant in cases of unclassifiable tumors, informing treatment and supplying data useful to single-cell scientists. This report highlights the electron microscopy findings of osteosarcoma. In this chapter, transmission electron microscopy is reviewed, and the current advantages and disadvantages of electron microscopy relative to molecular diagnosis are presented. Moreover, the most updated knowledge of the molecular biology and pathology of osteosarcoma is reported.