[43] FNCLCC Grading for Core Needle Biopsies of Soft Tissue Sarcomas Using Ki-67 Proliferative Activity and Radiologic Assessment of Necrosis

S Davion, X Lin, I Omar, W Laskin. Northwestern Memorial Hospital, Chicago, IL

Background: Optimal patient management for high grade soft tissue sarcomas (STS) may involve preoperative chemoradiation therapy. Core needle biopsies (CNB) are preferred for initial diagnosis of STS because of their efficiency and lack of morbidity, but grading such small samples proves difficult. FNCLCC combines mitotic index, % necrosis, and differentiation, for a three-tiered grading system and is used on surgical resection specimens. However it is poorly transferrable to the limited tissue of CNB.
Design: In this study, we correlated FNCLCC grade on CNB with final surgical excision FNCLCC grade for 17 biopsied and resected STS. For CNB we used Ki-67 immunoexpression instead of mitotic count and evaluated the amount of necrosis radiographically.
Results: The CNB FNCLCC grade accurately predicted the surgical specimen FNCLCC grade in 10 out of 16 cases (r = .60 , p = .005). FNCLCC grade between surgical excision and CNB never differed by more than one. Radiologic assessment of necrosis accurately predicted surgical specimen necrosis in 10/12 malignant cases (100 % sensitive, 75 % specific), and 2 out of 7 benign soft tissue tumors used as controls (28% specific). The FNCLCC CNB differentiation grade accurately predicted the surgical excision differentiation grade in 11 out of 16 (r = .38, p = 0.14) cases. Most discrepancies in differentiation grade occurred in the well differentiated liposarcoma group where more cellular/dedifferentiated areas, or areas not diagnostic of liposarcoma, were not sampled on the CNB. The Ki-67 index accurately predicted the surgical specimen FNCLCC mitotic grade in 8 of 13 cases (r=.48 p= .09). All CNBs with a Ki-67 index of less than 13% had a surgical mitotic FNCLCC grade of 1. The Ki-67 index of all 7 benign soft tissue lesions used as controls was less than or equal to 1%.
Conclusions: FNCLCC grading of CNB using radiologic assessment of necrosis and Ki-67 index to supplant mitotic activity shows a moderate degree of correlation with the surgical resection specimen grade using conventional FNCLCC criteria. CNB assessment of differentiation is least reliable in the well-differentiated liposarcoma group. Absence of radiologic necrosis in a malignant STS virtually assured its absence in the surgical resection specimen.
Category: Bone & Soft Tissue

Monday, March 9, 2009 9:30 AM

Poster Session I Stowell-Orbison/Autopsy Award # 15, Monday Morning