I would agree with the original hospital’s diagnosis: benign lipophyllodes tumor.

This is apparently a fibroepithelial tumor, but with adipose tissue component. The following features of this case support the above diagnosis: 1. Age 30 and tumor size 12 cm. 2. Not encapsulated, but it is demarcated. 3. The distribution of the stroma and epithelium is not symmetrical all around the tumor. It is disturbed in photo #4, with possible leave-like structures, even though the photo did not show the full view of it. Periductal concentration of the stroma cells is somewhat present, while the tumor stroma is not really that much hypercellular. 4. There is no stroma atypia, and no stroma mitosis identified. Those mitoses shown in the photo seem from epithelial cells.

The relatively unique feature for this case is the abundant adipose tissue as part of the fibroepithelial tumor, which is well documented in phyllodes tumor as lipomatous metaplasia.

The main differential diagnosis for this case is the periductal stromal sarcoma, which should be infiltrative, not as demarcated as in this case. The adipose tissue in periductal stromal sarcoma is not part of the tumor, but the adipose tissue being infiltrated by tumor, while in lipophyllodes tumor, the adipose tissue IS part of the tumor. Further, there should be no leave like structures in periductal stromal sarcoma. Most importantly, there are no sarcomatous features in this tumor (stromal cell atypia, mitosis).

I think “Chiang” could be the winner for this case. Even though his original comment was too simple, the comment he made latter on has hit the points.

Merry Christmas and Happy New Year!