A 49-year-old patient presented to our hospital with a mass on the left breast that had been growing during the past 4 years. On physical examination, the mass had a hard consistence and caused skin ulceration. No axillary nodes were found clinically.
Mammography and magnetic resonance could not be performed because of the tumoral size. Instead, an ultrasound was performed, followed by a CT scan. Cystic and solid components were found, as well as marked internal vascularity demonstrated by Doppler ultrasound. The mass occupied practically the whole breast and extension to the pectoral muscle was difficult to determine by physical examination.
On CT scan the mass appeared as a polilobulated lesion with areas of necrosis and heterogeneous density. The mass infiltrated the pectoral muscle without any invasion to other tissues in the anterior thoracic wall or metastatic extension to other organs.
Histology of a sample taken through fine needle biopsy of the mass was of a phyllodes breast tumour. As the mass infiltrated the pectoral muscle, the patient underwent unilateral mastectomy with reconstruction of the anterior thoracic wall. Final diagnosis after complete histological analysis of the resected mass was of a malignant phyllodes tumour, measuring 24 x 18 x 16 cm. with important stromal proliferation, partially sarcomatous degeneration, and 7 mitoses per field. As no signs of ganglionar extension were found, surgical treatment was consolidated with radiotherapy
Phyllodes tumours are fibroepithelial neoplasms that arise from epithelial and stromal breast tissue and that may have different tumoral behaviour according to the histological type (benign, borderline or malignant). The presence of an epithelial component differentiates the phyllodes tumours from other stromal sarcomas 
Clinically, Phyllodes tumours usually present as a big, smooth, macrolobulated, and painless mass with an initial slow growth pattern, and a latter accelerated growth phase. The average size for which the patients consult is around 4-7cm. Other signs such as skin ulceration, thoracic wall invasion or metastatic extension are uncommon. 
Some of the imaging characteristics might be related to the accelerated tumour growth, with areas of necrosis or cystic degeneration mixed with dense tumoral tissue and vast vascularization. A well-defined, lobulated mass that simulates a fibroadenoma is the typical appearance by mammography.
On ultrasound, it might be seen as a hypoechoic or heterogeneous mass with calcifications within it and increased vascularity on Doppler. . Although no specific radiological findings may be related to the histological type, some features on magnetic resonance imaging (such as the presence of a cystic component, strong lobulation, and heterogeneity on delayed-phase contrast-enhanced T1 weighted images) have been described and may helpful for distinguishing them from fibroadenomas. [1,3]
Final diagnosis is achieved through core needle biopsy by proving stromal and epithelial derangements that distinguish them from fibroadenoma and allow the histological differentiation of the tumour into benign, midline or malignant. 
Benign phyllodes tumours represent 60% to 75% of all phyllodes tumours. They exhibit uniform spindle-cell stromal nuclei, scarce mitoses (generally less than 5 per 10 high-power fields) and uniform borders. (X) As mitotic activity increases and stromal cellularity becomes greater, the tumour grade escalates.
Mitosis in borderline phyllodes tumours occurs more frequently (5 to 9 per 10 HPF), with focally invasive borders, increased stromal cellularity and moderate stromal overgrowth and atypia. They are usually diagnosed when criteria for malignant phyllodes is not met. 
Finally, malignant tumours have the highest grade of all histological variables: they exhibit marked nuclear pleomorphism of stromal cells, stromal overgrowth, 10 or more mitoses per 10 HPF, increased stromal cellularity which is usually diffuse, and infiltrative borders. 
Histological grade has been linked with prognosis and local recurrence (as well as inadequate local excision for this last one) and is considered a cornerstone for treatment individualization. Increased protein expression such as p53 and Ki-67 antigen have been detected in malignant phyllodes tumours and seem to correlate with negative prognostic factors as well. 
The treatment of phyllodes tumours is usually complete wide-local excision, with greater than 1 cm margins or mastectomy for large tumours. As 10% of patients with phyllodes tumours develop distant metastases, and these eventually occur in approximately 25% of malignant tumours, a more aggressive approach with chemotherapy and radiotherapy may be considered. The prognosis of Phyllodes tumours is good, with an 87% 10-year survival. [1,6]
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 Corso, D, et al, Tumor filoide. Estado del arte. Rev Colomb Cancerol.2016;20(2):79-86. DOI: http://dx.doi.org/10.1016/j.rccan.2015.10.001
 Takeshi Kamitani, et al. Differentiation between benign phyllodes tumors and fibroadenomas of the breast on MR imaging. European Journal of Radiology, 2014, 83;8, 1344-1349 DOI:https://doi.org/10.1016/j.ejrad.2014.04.031
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 Shashi Prakash Mishra, Satyendra Kumar Tiwary, et al. Phyllodes Tumor of Breast: A Review Article. ISRN Surg. 2013; 2013: 361469. (PMID: 23577269)
 Jing Wei, Yu-Ting Tan, et al. (2014), Predictive factors for the local recurrence and distant metastasis of phyllodes tumors of the breast: a retrospective analysis of 192 cases at a single center. Chin J Cancer. 2014 Oct; 33(10): 492–500. DOI: 10.5732/cjc.014.10048
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