Malignant tumors: an introduction

Childhood cancer is fortunately rare. In the USA, 129.5 cases per million of white children and 104.1 cases per million of black children under the age of 15 years develop a cancer, only 5% of which occur in the head and neck. Pediatric head and neck malignancies represent a spectrum of histological types, which are totally different from those found in adults. In adult patients, squamous cell carcinoma accounts for over 90% of head and neck cancers if facial skin cancers are excluded. In pediatric patients, the majority of malignancies consist of small, blue, round cell tumors (neuroblastoma, peripheral neuroendocrine tumor, Ewing's sarcoma, non-Hodgkin's lymphoma, and soft tissue sarcomas). If central nervous system and hematological malignancies are excluded, then retinoblastomas, rhabdomyosarcomas and neuroblastomas are the most common cancers. Below the age of 3 years, retinoblastomas are the most common, followed by rhabdomyosarcomas and neuroblastomas; from 3 to 11 years, rhabdomyosarcomas are the most common, followed by lymphomas, while from 12 to 21 years this order is reversed.

Recent advances in molecular biology have led to increased understanding of the role of chromosomal changes, suppressor genes, and oncogenes in the etiology of these neoplasms. In addition, electron microscopy, histochemical staining, identification of cell markers, immunofluorescence, etc., have enabled better tumor typing and classification. In the clinical arena, multimodal therapy incorporating surgery, radiation and chemotherapy has increased long-term survival.