[310] Histological Features Differentiating Cellular Fibroadenoma from Benign Phyllodes Tumor on Core Needle Biopsies

Saba Yasir, Roberto G Gamez, Daniel W Visscher, Aziza Nassar. Mayo Clinic, Rochester, MN

Background: Fibroepithelial lesions (FEL) of the breast are a heterogeneous group of tumors ranging from cellular fibroadenoma (CFA) to benign phyllodes tumor (BPT). Distinction between the two is challenging on core needle biopsy (CNB) and has a great impact on appropriate clinical management. The objective of this study is to evaluate the histological features of FEL on CNB that can help differentiating BPT from CFA on core needle biopsy.
Design: All patients diagnosed with FEL on CNB between 2002 and 2012 were retrieved from our anatomic pathology data base. Patients with subsequent excision were selected for further evaluation. Histopathological features were evaluated on CNB blinded to the excision diagnoses. These features included stromal overgrowth, mitoses per 10 high power fields (HPF), increased stromal cellularity, stromal fragmentation, adipose tissue infiltration, stromal heterogeneity, subepithelial condensation and stromal pleomorphism.
Results: See table #1

Table #1: Clinicopathologic Characteristics that Differentiate Cellular Fibroadenoma from Benign Phyllodes Tumor
 Fibroadenoma (N=43)Phyllodes (N=25)p-value
Age, mean (SD)39.0(14.5 )43.9(12.8)0.1499**
Stromal overgrowth17(39.5%)14(56.0%)0.1887
Mitosis =021(48.8%)4(16.0%)<0.0001
Increased stromal Cellularity38(88.4%)24(96.0%)*0.4024
Stromal Fragmentation24(55.8%)19(76.0%)0.0960
Adipose tissue infiltration9(20.9%)10(40.0%)0.0911
Subepithelial Condensation10(23.3%)16(64.0%)0.0009
Stromal pleomorphism20(46.5%)17(68.0%)0.0863
* Fisher's exact test, ** t-test, all of the rest chi-square test.

Conclusions: The presence of subepithelial condensation, stromal heterogeneity and more than 2 mitotic figures per 10 HPF on core needle biopsy are more predictive of benign phyllodes tumor than of cellular fibroadenoma. Other features studied, including stromal overgrowth, increased stromal cellularity, stromal fragmentation, adipose tissue infiltration and stromal pleomorphism are not helpful in differentiating these two entities on needle core biopsy.
Category: Breast

Monday, March 4, 2013 1:00 PM

Poster Session II # 42, Monday Afternoon


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