CA: A Cancer Journal for Clinicians, Vol 29, 66-77, Copyright
© 1979 by American Cancer Society
The Pathology of Tumors, Part III: Grading, Staging & Classification
Juan Rosai M.D.1 and
Lauren V. Ackerman M.D.2
1 Professor, Laboratory Medicine and Pathology and Director of Anatomic Pathology, Department of Laboratory Medicine and Pathology, University of Minnesota Medical School, Minneapolis, Minnesota.
2 Professor of Pathology, State University of New York, Stony Brook, New York.
Both grading and staging of neoplasms are used to give the therapist clues to the prognosis of cancer. Grading (I-IV) designates the relative differentiation of cells that compose the tumor (Grade I, highly differentiated to Grade IV, undifferentiated). In general, the prognosis deteriorates as the cells become less differentiated; however, grading gives no information about the prognosis of certain tumors (e.g., melanoma). Many pathologists prefer to grade tumors as well differentiated, moderately differentiated, poorly differentiated and undifferentiated rather than using the corresponding number.
Staging refers to the extent of tumor spread. Tumors are usually staged in numbers (I-IV); however, the clinical staging of some cancers has been standardized into the T (tumor) N (nodes) M (metastases) system of the International Union against Cancer.
The classification of tumors should be as simple as possible to avoid confusion and is most valuable when correlated with the clinical features, natural history and ultimate prognosis.
Carcinoma classification usually depends on the organ of origin, whereas sarcoma and lymphoma are generic terms and may be applied regardless of anatomic location. The designation of carcinoma in situ is used for a lesion that has all the histologic attributes of malignancy, except invasion. However, a small biopsy showing only carcinoma in situ may be the outer edge of an invasive cancer. In most cases carcinoma in situ will progress to invasive cancer if left untreated.
The classification of sarcomas has progressed from a descriptive (round cell or giant cell, etc.) to a histogenetic nomenclature (liposarcoma, leiomyosarcoma, etc.). The type, subtype and local extent of sarcomas will determine the best therapy for the tumor. In malignant lymphomas, exact histologic classification is particularly important, as some types (e.g., Hodgkin's disease) are now curable in most cases with appropriate therapy. The accurate diagnosis and classification of lymphoma is a difficult problem for the pathologist and requires great care in the preparation of tissue for examination.
