Malignant phyllodes tumor of the male breast

Abstract

A 75-year-old male patient presented with a palpable left breast lump and bloody nipple discharge. He had previously received hormonal treatment for prostate cancer. Physical examination revealed a hard left retroareolar mass and bilateral gynecomastia. Mammograms revealed bilateral gynecomastia and a partly obscured dense ovoid left retroareolar mass (Figure 1); ultrasound showed a corresponding complex solid-cystic mass (Figure 2). USguided core biopsy revealed malignant phyllodes tumor. Staging CT and bone scan showed no distant metastases. The patient underwent bilateral mastectomy. Gross specimen showed a complex cystic tumor. Histologic examination confirmed findings of malignant phyllodes, demonstrating an ill-defined fibroepithelial tumor with the epithelium showing leaf-like architecture with hypercellular spindle cells and stromal overgrowth. Tumor cells displayed moderate-marked nuclear pleomorphism with multinucleated giant forms and mitoses up to 10/10HPF (Figure 3A-F). Phyllodes tumors (PT) are uncommon neoplasms constituting less than 1% of all breast tumors and 2%-3% of fibroepithelial tumors and show varying malignant and recurrence potential. Phyllodes tumors are categorized into benign, borderline, and malignant according to the degree of stromal cellularity and atypia, mitotic count, presence or absence of stromal overgrowth, and tumor margin/infiltration. While PT have been reported in male prostate, urethra, and seminal vesicles; PT of the breasts occur almost exclusively in females—a literature review in 2003 searching back to 1838 found only 12 cases in men. Usually, there is pre-existing gynecomastia with some patients having received hormone therapy for prostate cancer similar to our patient. On mammography, PT are usually ovoid or lobulated, generally well-circumscribed masses. Ill-defined margins are less common, suggesting a more aggressive histology. Ultrasound shows solid circumscribed ovoid or lobulated masses or complex cystic masses, often with increased vascularity on Color Doppler. Characteristic sonographic findings include intra-tumoral cystic spaces and linear