Phyllodes Tumor Phyllodes tumors are rare fibroepithelial tumors that display a spectrum of clinical and pathologic behaviors that are benign, borderline, and malignant (154,155). The distribution of phyllodes tumors demonstrates that most tumors are benign (70%) compared with malignant (23%) and borderline lesions (7%) (156). This distribution is similar to a larger, older study that reported an incidence of 64% benign, 21% malignant, and 14% borderline phyllodes tumors (157). The incidence in some studies should be viewed with caution because of variation in histologic interpretation (156). Phyllodes tumors may occur at any age but tend to be more common in women who are in their late 30s, 40s, and 50s (156,158–162). These lesions are rarely bilateral and usually appear as isolated masses that are difficult to distinguish clinically from a fibroadenoma. Patients often relate a long history of a previously stable nodule that suddenly increases in size. Reported sizes range from 1.0 to 50 cm (154,163,164). Size is not a dependable diagnostic criterion, although phyllodes tumors tend to be larger than fibroadenomas, probably because of their rapid growth. There are no good clinical criteria by which to distinguish a phyllodes tumor from a fibroadenoma. Whereas observation of a fibroadenoma is acceptable, excision of a phyllodes tumor is necessary for local control and for determination of benign or malignant features. To avoid unnecessary excision of benign fibroadenomas that are indistinguishable from phyllodes tumors on clinical examination, imaging criteria were sought to aid in identifying patients who require EB for complete histopathologic evaluation and local control. Mammography may show a halo around a phyllodes tumor mass but cannot reliably distinguish a fibroadenoma from a phyllodes tumor (165–167). Ultrasonography evaluation has limitations even when color and pulse Doppler ultrasonography are used in conjunction with it (163).
Microscopic evaluation of a lesion is important to determine the diagnosis. The histologic distinction between fibroadenoma, benign, borderline, and malignant phyllodes tumor can be very difficult on minimal tissue sampling with FNAC or CNB (168,169). It may be easier to distinguish benign phyllodes from malignant phyllodes tumors than benign phyllodes tumors from fibroadenomas (170). Histologic features that stratify lesions include number of mitoses per high power field, stromal cellularity, pushing or infiltrating tumor margin, cellular atypia, tumor necrosis, and stromal overgrowth (171).
If a lesion cannot be clearly characterized as a fibroadenoma, excision may be necessary.
Factors that are considered in recommending excision include older age, new mass in a well-screened individual, rapid growth, size greater than 2.5 to 3 cm, suspicious FNAC or CB, and mammographic or ultrasonographic features that demonstrate lobulation and intramural cysts. If observation is elected, repeat clinical examination and imaging in a short interval is essential to evaluate change in size.
Treatment of biopsy-proven phyllodes tumor is wide local excision, attempting to obtain a 1-to 2-cm margin (156–161). Massive tumors, or large tumors in relatively small breasts, may require mastectomy; otherwise, mastectomy should be avoided, and axillary lymph node dissection is not indicated. Often, however, a patient will undergo excisional biopsy of a mass believed to be fibroadenoma, and final histologic examination reveals a phyllodes tumor. Reexcision with normal breast margins is recommended for borderline and malignant phyllodes tumors (159). An expectant approach is an option for unanticipated diagnosis of benign phyllodes tumors (157).