New Tumor Classification System Proposed

National Cancer Institute's Cancer Diagnosis Program (Bethesda, MD, USA). "This classification is simple (reducing the complexity of information received from the molecular analysis of tumors), comprehensive (providing a place for every tumor of man), and consistent with recent attempts to characterize tumors by cytogenetic and molecular features,” he explains.

Although tumors in the past have been classified by their morphologic appearance, he notes that tumors with similar histologic features can follow different clinical courses. Thus, a classification based solely on the molecular characteristics of tumors would sacrifice the clinical/pathologic experiences that inform almost every clinical decision related to the diagnosis and treatment of cancer patients. The type of cells from which a tumor derives as well as the molecular characteristics of those cells determine the behavior of the tumor, so both are important pieces of information to clinicians. Dr. Berman has organized his classification around these two features.

At the highest level of classification, tumors are grouped according to the developmental history of the component cells, or their histogenesis. For example, leukemia would be classified as a mesenchyme-derived tumor. Patterns identified from the gene expression and proteomic data from tumor samples can then be integrated as new groups in this classification.

"Some of these groupings will prove to have a specific biologic feature, for example, an increased tendency to metastasize, a higher response to a chemotherapeutic agent, or lengthened survival,” notes Dr. Berman.

Since each tumor is derived from a cell with an individual lineage, it will have a unique position within the classification. Currently, the commonly used tumor classifications list tumors by the body site of origin. However, each organ contains connective tissue, vessels, and lymphoid tissue. When listing the tumors that can occur in an organ, it becomes obvious that every organ can develop many of the same tumors. So classifications that are organized by anatomic site become massively redundant. This becomes a major problem when dealing with thousands of tumor terms that link to other biologic datasets.

"A good classification system should help drive down the complexity of enormous databases and help us discover relationships among different data elements by assembling data under sensible group hierarchies,” Dr. Berman points out. "The most important value of this classification is the disengagement of tumor type and tumor place of origin […]. This permits tumors with similar molecular profiles to be classified according to biological attributes rather than anatomical location.”

Dr. Berman's article on the classification system was published in the March 17, 2004, online journal BMC Cancer, of Biomed Central. Dr. Berman's classification outline and the latest version of the classification (with 55,000 entries) are available as supplemental open access documents that can be used or criticized freely by the biomedical community.




Related Links:
National Cancer Institute
Biomed Central