UICC-2002 TNM classification is not suitable for differentiated thyroid cancer in children and adolescents.

Background. Recently the UICC-TNM classification for differentiated thyroid cancer (DTC) was changed neglecting the special circumstances for children affected by the disease. While the 1997 TNM classification grouped tumours <= 1 cm as T1, the 2002 system changed this to a margin of <= 2 cm. The consequences of this change were evaluated by analysing patients enrolled in the multicentre interdisciplinary therapy study of the German Society of Paediatric Oncology and Haematology (GPOH) on malignant endocrine tumours in children and adolescents, GPOH-MET 97. Procedure. Between 1998 and 2005, 82 patients with histologically proven DTC entered the study. Patients classified according to UICC-TNM classification 1997 were reclassified according to the new classification (2002/2003) and vice versa by cross checking with original pathologist's reports. Results. Twenty males and 62 females at a mean age of 12.5 years were evaluated. We observed a definite shift from patients formerly classified as T2 (1-4 cm) to category T1 (<= 2 cm) according to the 2002 TNM classification. Among these patients a threefold increase of lymph node involvement and/or distant metastases Could be demonstrated. Conclusions. The 2002 UICC-classification may have a disadvantage for children with tumours measuring between 1 and 2 cm, as those are now classified as T1. A high rate of lymph node involvement in this group reflects the risk of under-diagnosis and -treatment of this group. The current TNM classification for DTC in children should be changed taking the physiological and anatomical differences between children and adults into consideration.