Giant Borderline Phyllodes Tumor Fungating Through the Skin as Fleshy Polypoid Outgrowths

We present the case of a 52-year-old female with a giant phyllodes tumor (GPT), which was fungating through the skin that showed fleshy polypoid outgrowths. Histological analysis revealed stromal atypia, mitotic activity, and stromal overgrowth; however, the tumor border was well-defined, and malignant heterologous elements were not observed. Therefore, as some but not all malignant histological characteristics were present, we diagnosed the patient with borderline GPT. In cases of phyllodes tumor (PT) with the unique gross findings of fungation through the skin as fleshy polypoid outgrowths, caution is required for the subsequent course because even if the PT is graded as benign histologically, a malignant process can occur. Pathologists should note that the sampling of the collection site and the ambiguity of the histological grading of PT may affect the final diagnosis of GPT. It is also important to perform surgery with adequate preservation of the resected margins to control recurrence for patients with GPT.