Gastrointestinal stromal tumors (GIST) from risk stratification systems to the new TNM proposal: more questions than answers? A review emphasizing the need for a standardized GIST reporting.

Following the successful introduction of the receptor tyrosine kinase inhibitors (TKI) as the mainstay for the treatment of advanced and metastatic gastrointestinal stromal tumor (GIST), GIST has received a special attention in the recent literature. This resulted in major achievements on the surgical pathology diagnosis and improved our understanding of the molecular biology of the disease. Availability of the effective TKI therapy has emphasized the need for a more reliable and reproducible system for assessment of the malignant potential in GIST to allow for an optimal individualized patient treatment. All of the risk stratification systems proposed so far have emphasized the value of tumor size, mitotic count and anatomic site for risk estimation, at the same time appreciating the difficulty of classifying individual tumors as either benign or malignant. The newly proposed UICC TNM classification for GISTs represents the most recent hallmark on this topic; yet its usefulness remains to be tested in future clinical studies. This review briefly summarizes and discusses the most pertinent risk systems proposed for assessment of the malignant potential of GIST stressing their advantages and limitations and including some critical remarks on the newly proposed UICC TNM system for classifying GIST. Most importantly, an emphasis is made on the urgent need for a standardized approach for histopathological evaluation and reporting of GIST specimens to allow for a reproducible tumor size, mitotic count and tumor growth pattern, and hence for a better risk classification.