Comparative study of histological features between core needle biopsy and surgical excision in phyllodes tumor.

We analyzed histopathological features of core needle biopsy (CNB) and surgical excision specimen comparatively in 129 patients with surgically proven phyllodes tumor (PT). Stromal characteristics including cellularity, atypia, mitosis, overgrowth, tissue fragmentation, and the tumor margin were assessed. Benign/borderline/malignant phyllodes tumor (PT) were diagnosed in 90 (69.8%)/30 (23.3%)/9 (7.0%) patients. Among the 90 cases of benign PTs, 67 cases (74.4%) were diagnosed concordantly in CNB. For borderline and malignant PTs, three out of eight (26.6%) and four out of nine (44.4%) cases were diagnosed concordantly in CNBs. All 50 cases of discordant diagnosis were underestimated in matched CNBs, especially in their stromal cellularity and mitosis. The size of tumor is larger in discordant cases of PT (P= 0.013). The concordant rate of diagnosis between CNB and surgical excision was about 60% and accordingly, grading of PT based on the histological findings in CNBs has limitation. The discordance comes from heterogeneous stromal properties of PTs.