Needle core biopsy in the diagnosis of phyllodes neoplasm.

BACKGROUND: Accurate identification of phyllodes neoplasms without surgical intervention is difficult, reducing the ability to manage "benign" lumps non-operatively and impacting on the open benign biopsy rate. Needle core biopsy is considered to be a highly accurate technique in the diagnosis of breast carcinoma. Its accuracy in the diagnosis of phyllodes neoplasm has not been established.
METHODS: A series of 3729 core biopsies performed between January 1999 and July 2005 were examined. All core biopsies followed by surgical excision were identified. Histologic concordance between core biopsy and excision specimen was analyzed.
RESULTS: Twenty-three patients had phyllodes neoplasm on excisional biopsy with prior core biopsy findings as follows: phyllodes neoplasm (n=2), "equivocal" for phyllodes neoplasm (n=12), fibroadenoma (n=3), benign (n=6). The false negative rate for phyllodes neoplasm was therefore 39% (n=9/23). Of the total biopsy series, 35 patients had a core biopsy suggesting the possibility of phyllodes neoplasm. Of these, 32% (n=11) were found to be phyllodes neoplasm on excision, 3% (n=1) phyllodes neoplasm with breast carcinoma, 6% (n=2) breast carcinoma, and 3% (n=1) sarcoma. When a preference for phyllodes neoplasm (n=4) was stated on the equivocal core biopsies, excision correlated with the stated preference; this correlation also occurred in 90% (n=9/10) of core biopsies where fibroadenoma was favored.
CONCLUSIONS: Needle core biopsy rarely produces a definite preoperative diagnosis of phyllodes neoplasm. A diagnosis of fibroadenoma or equivocal phyllodes neoplasm on core biopsy should not prevent excision if clinical suspicion remains.