Grading and tissue-specific diagnosis

Abstract

Characterization consists of both grading and tissuespecific diagnosis. While tissue specific diagnosis implies pathological typing, grading implies a differentiation between benign and malignant tumors and definition of malignancy grade. Although pathology will always remain the gold standard in the diagnosis of soft tissue tumors, prediction of a specific histologic diagnosis remains one of the ultimate goals of each new imaging technique [34]. Moreover, decisions regarding biopsy and treatment could be simplified if a specific diagnosis or a limited differential diagnosis could be provided on the basis of imaging [1, 36]. Sundaram stressed the importance of naming soft tissue masses based on MR imaging criteria,working on the premise that ones inability to name, or provide a succinct differential diagnosis requires the lesion to be considered indeterminate and biopsied. The approach to such indeterminate lesions is that they are sarcomas until microscopically proven otherwise [38]. Benign soft tissue tumors outnumber their malignant counterparts by about 100 to 1. Otherwise most cutaneous and subcutaneous masses are very small and are often excised without imaging studies. As a consequence 60% of the soft tissue tumors in adults who are referred for evaluation by medical imaging are benign, this proportion increasing to 75% in the pediatric age group. The major role of grading consists merely in recognizing benign soft tissue tumors which will be excluded from further invasive diagnostic and therapeutic procedures. The statement that disease stage and grade are more important than tumor type with respect to five-year survival (American Joint Committee of Soft Tissue Sarcomas) [23] was discussed at the 20th anniversary meeting of the Soft Tissue and Bone Sarcoma Group of the European Organization for Research and Treatment of Cancer (EORTC) in Amsterdam (April 1113, 1996). There was a broad consensus that staging and grading systems should always be based on tumors of one specific histological type, because conventional staging and grading parameters are of different importance in different tumor types.Also the significance and the predictive value of the various histologic parameters vary in different types of sarcoma. And because of morphologic variations in different portions of the tumor, the grade is determined on the basis of the least differentiated area and its extent [19, 24, 53]. The pathologists perspective on grading is well described in Chap. 8.