Mammary Liposarcoma: A Clinicopathologic and Molecular Analysis.
Pamela L Lyle, Jean F Simpson, Julia A Bridge, Justin M Cates, David L Page, Melinda E Sanders. Vanderbilt University Medical Center, Nashville, TN; University of Nebraska, Omaha
Background: Primary sarcomas of the breast are rare, usually occurring in the setting of malignant phyllodes tumor. Heterologous differentiation can occur, most commonly as liposarcoma. Liposarcomas arising in this setting are histologically indistinguishable from liposarcomas of soft tissue, and include well differentiated, dedifferentiated, myxoid, and pleomorphic subtypes. In soft tissue, the different subtypes have distinct biologic behavior and genetic alterations including MDM2 and CDK4 amplifications, t(12;16) translocations, and polyploidy with complex structural rearrangements, respectively.
Design: We evaluated the clinicopathologic characteristics of mammary liposarcomas from the Vanderbilt Breast Pathology Consultive Practice. Liposarcomas were classified using criteria in the WHO classification system. A subset of cases was also subjected to FISH studies using a commercially available MDM2 probe and custom-designed CDK4 probe at the University of Nebraska Medical Center.
Results: Eighty cases of mammary liposarcoma were retrieved from the consultation files. All patients were women, ranging in age from 14 to 96 years, with a mean age of 52 years. All tumors were unilateral and showed an equal distribution of sidedness. Eighty percent of liposarcomas occurred in the presence of a phyllodes tumor. Liposarcoma was classified as follows: 50% well-differentiated, 30% myxoid, 15% de-differentiated and 5% pleomorphic. Molecular cytogenetic analysis revealed extra copies of chromosome 12, but not amplification for either CDK4 or MDM2 in two dedifferentiated liposarcomas.
Conclusions: Malignant phyllodes tumors often contain liposarcomatous elements that are histologically similar to those of soft tissue. Preliminary molecular studies suggest a lack of genetic alterations that are characteristically found in soft tissue liposarcomas. This may account for the markedly different clinical behavior of mammary liposarcoma which includes local recurrence but extremely rare incidence of distant metastasis.
Monday, February 28, 2011 1:00 PM
Poster Session II # 47, Monday Afternoon