Phyllodes tumors of the breast are fibroepithelial neoplasms that have the potential for recurrence and metastases. Grading into benign, borderline, and malignant categories is based on a constellation of histological characteristics that include the degree of stromal hypercellularity, stromal cytologic atypia and mitotic activity, stromal overgrowth, and circumscribed vs. invasive margins 2
. Although histological features have been helpful to some extent in predicting biologic behavior, specific parameters that can define the likelihood for recurrence are not universally accepted. Various investigators have found cellular pleomorphism, stromal overgrowth, tumor necrosis and heterologous stromal elements, or a combination of histological features to be prognostically useful. On the other hand, several authors have concluded that adequacy of surgical margins is of paramount importance and that histological factors have an inconsistent influence on biologic behavior 3
Sarcomatous stromal elements, including angiosarcoma, chondrosarcoma, leiomyosarcoma, osteosarcoma, and rhabdomyosarcoma, are rarely encountered in malignant phyllodes tumors 4
. Liposarcomas may also develop as stromal components of phyllodes tumors. Liposarcomatous differentiation in phyllodes tumors may consist of well differentiated, myxoid, round cell, and pleomorphic liposarcomatous elements 5
. The finding of a malignant heterologous element places the tumor into a malignant category 3
On gross examination, a typical phyllodes tumor is notable for leaf-like fronds projecting into cystic spaces. Many phyllodes tumors, however, are simply solid and vaguely lobulated. Well developed fronds consist of epithelial-lined stromal projections that protrude into dilated glands or cystic spaces. The glands are usually widely spaced, dilated, and irregular with prominent side branches. The epithelium is often hyperplastic, and atypical columnar cell hyperplasia is a common finding. Rare tumors show lobular and ductal carcinoma in-situ. Apocrine and squamous metaplasia is occasionally seen 6-8
To the best of our knowledge, we are reporting the first case in which an epithelial component of phyllodes tumor is identical to that of a tubular adenoma of the breast. And this is in addition to very rare liposarcomatous stromal differentiation in malignant phyllodes tumor. This tumor does not represent a collision tumor, i.e. tubular adenoma being immediately adjacent to the phyllodes tumor, because macroscopically cut section did not show separate masses, and microscopically lipoblasts widely infiltrated among epithelial glands. This tumor further expends the phenotypic features of phyllodes tumor.