Characteristics of fibroepithelial tumor
Biplastic, having proliferation of both stromal and epithelial components,[notes 1] arranged into either a pericanalicular pattern (stromal proliferation around epithelial structures), or an intracanalicular pattern (stromal proliferation compressing the epithelial structures into clefts).
Characteristics of fibroadenoma
Fibroadenomas characteristically display hypovascular stroma compared to malignant tumors. Furthermore, the epithelial proliferation appears in a single terminal ductal unit and has duct-like spaces surrounded by a fibroblastic stroma. The basement membrane is intact.
Characteristics of phyllodes tumor
In contrast to fibroadenomas, phyllodes tumors display a leaf-like architecture, and an increased stromal cellularity. In needle biopsy specimens, phyllodes tumors can be diagnosed in a fibroepithelial tumor if there is prominent mitotic activity of ≥3 per 10 high power fields, or the finding of 3 or more of the following characteristic histologic features:
- Stromal overgrowth
- Fat infiltration
- Stromal fragmentation
- Subepithelial stromal condensation
- Stromal nuclear pleomorphism
After diagnosing a fibroepithelial tumor, still exclude another type of breast cancer, which may arise within it:
Breast cancer types
|Invasive ductal carcinoma (IDC)||Carcinomatous cells are seen below the basement membrane of lactiferous ducts. Otherwise, there are no specific histologic characteristics, essentially making it a diagnosis of exclusion.|
|Ductal carcinoma in situ (DCIS)||Malignant epithelial cells confined to the ductal system of the breast, without invasion through the basement membrane.|
|Invasive lobular carcinoma (ILC)||The "classic" pattern is round or ovoid cells with little cytoplasm in a single-file infiltrating pattern, sometimes concentrically giving a targetoid pattern.|
|Lobular carcinoma in situ (LCIS)||
Cells have indistinct cell borders, pale cytoplasm, and uniform small nuclei with evenly distributed chromatin and inconspicuous nucleoli.
If, even after consultation, it is not clear whether a tumor is a fibroadenoma or phyllodes tumor, then it can be reported as a cellular fibroepithelial lesion or a fibroepithelial neoplasm.
A phyllodes tumor warrants a comment whether margins are positive or negative for tumor, whereas fibroadenoma does not need such comment.
Example report of fibroadenoma:
|Right breast, lumpectomy:|
- The proliferation of two histological components is called "biplasia", from Latin bis (“twice”) and -plasia (“formation”), or "biphasic proliferation" (although the latter may refer to proliferation that has two chronological phases).
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