Phyllodes Tumor Containing Invasive Ductal Carcinoma: A Rare Case Description & Review of Literature

Phyllodes tumors are uncommon, often benign, malignancies of the breast and account for approximately 0.5% of all breast malignancies. These tumors were first described in 1838 by Johannes Muller as cystosarcoma phyllodes and were later more aptly renamed phyllodes tumors (as they were neither cystic nor sarcomatous).(1) As a mixed connective tissue and epithelial tumor, these behave similar to benign fibroadenomas, though their growth is much more rapid and they tend to occur in older patients.(2) Hallmarked by their large size at presentation, these tumors average between 4 and 7 cm at the time of diagnosis. The only known risk factor for development of a phyllodes tumor is Li-Fraumeni syndrome.(1) Pathology of a phyllodes tumor is similar to that of a fibroadenoma though with increased cellularity and added whorled stroma which forms large clefts lined by epithelium resembling leaf-like clusters.(2) Mammography and ultrasound are unable to distinguish these tumors from a fibroadenoma as they show similar rounded borders. As a result, core needle biopsy is the preferred method of diagnosis, followed by complete wide excision with 1 cm margins to prevent local recurrence. Lymph node dissection is not required as lymph node metastasis is rare.(3) Review of SEER data showed only 8 of 498 women with phyllodes tumors had nodal involvement.(1) 50% of phyllodes tumors are entirely benign, however the remaining 50% are split between histologic designations of borderline (25%) and malignant (25%) after excision. Borderline and malignant histologies are characterized by increased stromal cellularity, atypia, mitotic rate, and presence of stromal overgrowth with infiltrative margins. These borderline and malignant tumors tend to have courses most similar to sarcoma of the trunk and spread hematogenously.(1) Only rarely in the literature have cases of invasive ductal cancer been reported in the background of a benign or borderline phyllodes histology