Grading of spindle cell sarcomas in fine-needle aspiration biopsy specimens

We studied whether histologic criteria for grading sarcomas could be applied to fine-needle aspiration biopsy (FNAB) specimens of adult spindle cell sarcomas, without knowledge of the sarcoma subtype, by reviewing 36 specimens. Grade 1 was assigned for minimal nuclear atypia and overlap, no necrosis, and rare mitotic figures, and grade 2 for moderate nuclear atypia, at least moderate nuclear overlap, appreciable mitotic figures, and necrosis. Severe nuclear atypia distinguished grade 3 from grade 2. A major noncorrelation between FNAB and histologic grades was defined as a misclassification of grade 1 vs grade 2 or 3. FNAB grades assigned were grade 1, 1; grade 2, 25; and grade 3, 10. There was 1 major noncorrelation due to a probable FNAB interpretation error. In 15 of 16 FNAB specimens of grade 2 or 3 sarcomas lacking mitotic figures, necrosis, or both, the nuclear atypia reflected the grade. In the remaining case, the degree of nuclear overlap and necrosis determined the grade. The histologic grading of sarcomas can be applied accurately to most FNAB specimens of spindle cell sarcomas without knowledge of the sarcoma subtype.