[Rare tumours--are they really rare in the Polish children population?].

Clear statement that pediatric neoplasms are really rare is not easy. Thus the incidence of rare tumours in children has not been defined so far. The paper efforts to assess the topic of rare tumours of childhood in the Polish population. Following two categories are proposed: tumours typical for adults, but possible in children (neoplasms of epithelial origin--mainly carcinomas, melanomas, carcinoids) and paediatric tumours consisting less than 10% of cases in corresponding clinical groups according to the ICCC classification. Data on 317 patients aged 0-18 years treated in centres associated in the Polish Paediatric Group for Solid Tumours (PPGST) were analysed. Classical adult malignancies were registered in 130 patients: carcinomas in 90 (mean age 12.6 +/- 4.5 years), melanomas in 25 (mean age 9.4 +/- 4.9) and carcinoids in 9 (mean age 14.5 +/- 1.2 years). Non epithelial neoplasms were registered in 187 patients (mean age 10.4 +/- 5.5). That group included rare tumours of soft tissue, CNS, bones and other organs. Treatments of certain groups were specified by separate therapeutic protocols within PPGST. Rare malignancies of adult-type among children under 18 years of age in Poland comprised 1.5% of all pediatric neoplasms. The incidence of adult-type neoplasms increased with age until 14 years. In patients over 15 years of age the number of registered cases decreased. It may suggest a first peak of incidence in early adolescence or an underestimation of number of patients with carcinoma aged over 15 years. In the analyzed group, the mean age of patients with carcinomas and other epithelial and unspecified tumours significantly exceeded the age of children with rare neoplasms of non-epithelial origin (12.1 +/- 4.7 vs 10.4 +/- 5.5 years; p<0.05). A very young age at diagnosis of malignant melanomas (mean 9.4 years) and numerous cases of carcinomas affecting the digestive tract (n=24; 27% of all carcinomas), especially those located in colorectal region (n=10), seem surprising. The preliminary analysis of the collected data on rare neoplasms in Poland encourage to undertake a prospective study, meant to link the epidemiology and characteristics of rare epithelial tumours in childhood with diagnostic and therapeutic suggestions for these types that are not coordinated within Polish Paediatric Group of Solid Tumours.