1. Principles and limitations of histologic diagnosis Standard parameters of diagnosis Pattern recognition Resemblance to normal histology Cost and availability Adult vs. pediatric tumors

2. Principles and limitations of histologic diagnosis Standard parameters of diagnosis

3. Parameters used in diagnosis of pediatric tumors Clinical features Primary sites Metastatic patterns Radiographic features

4. Parameters used in diagnosis of pediatric tumors Gross appearance Microscopic appearance –histologic pattern –tumor cell cytology Immunohistochemistry Electron microscopy Cytogenetics/molecular pathology

5. Principles and limitations of histologic diagnosis Standard parameters of diagnosis Pattern recognition

6. Pediatric Pathology Review Groups Children’s Oncology Group –Pediatric Oncology Group –Children’s Cancer Group –Intergroup Rhabdomyosarcoma Study Group –National Wilms Tumor Study Group SIOP CWS

7. Principles and limitations of histologic diagnosis Standard parameters of diagnosis Pattern recognition Resemblance to normal histology

8. Cellula est cellulas omnia (i.e. tumor cells come from normal cells). Rudolph Virchow

9. Principles and limitations of histologic diagnosis Standard parameters of diagnosis Pattern recognition Resemblance to normal histology Cost and availability

10. Test availability hierarchy Routine histology Immunostains EM Cytogenetics Molecular testing Gene arrays

11. Relative costs* (*Mayo, Clonitech)

12. Relative turnaround times

13. Principles and limitations of histologic diagnosis Standard parameters of diagnosis Pattern recognition Resemblance to normal histology Cost and availability Adult vs. pediatric tumors

14. Summary Histologic diagnosis is part of a synthesis of clinical and pathological data. Pattern recognition is the major technique used in histologic diagnosis and is a talent akin to bird- watching. Diagnosis of tumors is based in part on their resemblance to normal cells.

15. Summary, cont. Histologic examination is currently the most cost effective, readily available, and time efficient method of diagnosis. Tumor diagnosis in children differs markedly from that of adults, but in some circumstances (e.g. sarcomas) it is the same.