Malignant phyllodes tumor of the breast: report of two cases and a rare association

Leandro G. Oliveira, Barbara A. Barbosa, Elaine X. Machado, Thamires S. Lopes, Ana Cláudia G. Lima, Alexandre M.X. de

Jesus, Sebastiao A. Pinto, Juarez A. de Sousa – Instituto Goiano de Oncologia e Hematologia (INGOH).

Introduction:

Phyllodes tumors (PT) represent less than 1% of all breast tumors. Most of them are benign, but up to 30% show malignant

stroma. Malignant PT of the breast (MPTB) are characterized by marked stromal cellularity, atypia and high mitotic rate (> ou

= a 10 per 10 high-power fields). Unlike benign PT, MPTB can be clinically aggressive, with local recurrence rates ranging from

23–30%. Malignant change of the epithelium in MPTB is rare. The most frequent occurrence is infiltrating carcinoma of various

types while ductal carcinoma in situ (DCIS) is more rare. The purpose of this study was to present two cases of MPTB, one of

them with a concomitant DCIS.

Case reports:

Case 1: A 49-year-old female patient presented a history of mass in the right breast with accelerated growth. Core biopsy was

compatible with a fusocellular neoplasm. Patient underwent simple mastectomy with surgical margins free. Macroscopy

evidenced a 12x11cm lesion. Immunohistochemistry (IHC) showed a tumor with high mitotic rate (12 mitoses/hpf), ki-67 10%,

CD-34 and vimentin +, S-100 protein and AE1/AE3 ceratines -, compatible with malignant phyllodes tumor.

Case 2: A 54-year-old female patient presented with a firm mass in the left breast with accelerated growth. Core biopsy was

compatible with a low grade MPTB (6 mitoses/hpf). IHC was positive for CD-3 and vimentin and ki-6715%. Patient underwent

left adenomastectomy with sentinel node biopsy. The features were consistent with MPTB of 4,5 x 3,0cm. The epithelial

component showed a 0,7×0,6cm DCIS, nuclear grade 2, solid with hormonal-receptors positives (>90%). Surgical margins were

free of tumor.

Discussion:

PT represent a specific subset of breast soft tissue tumors composed of a connective stroma and epithelial elements. These

epithelial components may show a range of metaplastic (apocrine, squamous) and proliferative changes. However, DCIS in

association with PT is extremely rare, with only few cases reported in the literature. The role of adjuvant radiation or

chemotherapy following partial breast surgery (PBS) or mastectomy is still unclear due to the rarity of these tumors.

Conclusion:

In this study, we described a MPTB that harbored an intraductal carcinoma. This result could determine an absolute indication

for adjuvant radiotherapy if the patient underwent PBS. Although the stroma in these tumors is commonly the aggressive

component, the epithelial component also requires close and careful histological appraisal.

Key words:

Phyllodes tumors, malignant phyllodes, breast cancer, intraductal carcinoma.