Abstract

Phyllodes tumors are uncommon fibroepithelial breast tumors accounting for less than 1 percent of all breast neoplasms. To the best of our knowledge, only two cases of cutaneous metastatic malignant phyllodes have been reported in the literature (scalp and trunk). We report a third case of cutaneous metastatic malignant phyllodes tumor to an extremity. A 71- year old female presented with two distinct cutaneous lesions, one involving her left proximal lateral arm (2.5 cm) and one involving her left lateral chest (1 cm). Concurrently the patient was noted to have mass lesions in her lung and right breast. A punch biopsy of the arm lesion was performed. Histological examination revealed a dermal infiltrate of severely atypical epithelioid cells with pleomorphic nuclei and frequent mitoses. The findings were initially concerning for melanoma; however, the tumor cells were negative for Melan A and SOX-10. Review of the patient’s clinical history was significant for a malignant phyllodes tumor of left breast treated with wide local excision with > 1 cm tumor free margins followed by adjuvant radiation therapy. Subsequently, the dermal infiltrate was found to be morphologically similar to the patient’s primary breast tumor supporting the diagnosis of cutaneous metastatic malignant phyllodes tumor. This case demonstrates the importance of clinical history and immunohistochemistry when evaluating cutaneous poorly differentiated epithelioid neoplasms.

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