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

Principles and limitations of histologic diagnosis Standard parameters of diagnosis

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

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

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

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

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

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

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

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

Relative costs* (*Mayo, Clonitech)

Relative turnaround times

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

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.

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.