Case 10 Clinical history Female 42 years. Six years previously she had a fibroadenoma removed from each breast. She was sent back to the Breast Clinic because she had developed two further lumps in the right breast. Ultrasound showed both to be solid and well defined. FNAC from both showed benign cells only - C2. Excision biopsies were performed because the larger of the lesions measured more than 3 cm clinically. Histological appearances - A-D Two blocks from the larger lesion are provided. In one the typical appearances of a fibroadenoma are seen (A) with an intracanalicular pattern and loose cellular stroma. The latter shows no nuclear atypia. In the other block from a different area of the lesion (B-D) there are definite leaf-like structures with deep epithelial clefts, and the stroma is very cellular with closely packed spindle-shaped nuclei, some showing slight nuclear atypia. Mitoses are infrequent. Differential diagnosis 'Cellular' fibroadenoma Phyllodes tumour The combination of the leaf-like pattern and cellular stroma in part of the lesion point to a diagnosis of phyllodes tumour arising in a pre-existing fibroadenoma. The edge is well defined, there is little nuclear pleomorphism and the mitotic count is low, all features of a benign phyllodes tumour. NB The other lesion in the breast was a simple fibroadenoma. Final diagnosis Benign phyllodes tumour arising in a fibroadenoma. Learning points - Cases 9 and 10 · Size alone is not a helpful distinguishing feature between fibroadenoma and phyllodes tumour. · A diagnosis of phyllodes tumour requires a combination of deep epithelial clefts and a cellular stroma. · Some phyllodes tumours appear to arise in pre-existing fibroadenoma. · Adequate sampling is required to make the correct diagnosis in large fibroepithelial lesions. · The main points of distinction between benign and malignant phyllodes tumour are margin definition, stromal nuclear pleomorphism and mitotic counts. |
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