[272] The Spectrum of Osteosarcomatous and Chondrosarcomaous Differentiation in Malignant Breast Lesions

Corinne L Stephenson, Jean F Simpson, David L Page, Melinda E Sanders. Vanderbilt University Medical Center, Nashville, TN

Background: Osteosarcomatous (OSD) and chondrosarcomatous differentiation (CSD) in malignant breast lesions is rarely encountered. These heterologous sarcomatous elements have an identical histologic appearance as their extramammary counterparts. However, limited cytogenetic and molecular studies suggest that they do not share the same changes which may explain their usually less aggressive behavior in the breast.
Design: We reviewed the histopathology of malignant breast neoplasms with OSD and/or CSD received by the Vanderbilt Breast Consultation Service from July 1997 to September 2011 to identify features useful for their correct classification. Available slides and reports were reviewed and diagnostic features were recorded. Immunohistochemical (IHC) studies had been performed on select cases.
Results: Eighty-seven cases with OSD and/or CSD were identified and had been diagnosed as follows: metaplastic carcinoma (n=51), malignant phyllodes tumor (n=17), and sarcoma only (n=19). Patients with sarcomas were slightly older (average 69 vs. 60 yrs) than patients with metaplastic carcinomas and phyllodes tumors, but there was no size difference among the 3 groups. Within the metaplastic carcinomas, 25 showed OSD, 18 had CSD and 8 were mixed. In addition, 15 metaplastic carcinomas contained no special type carcinoma components (one of which had 2 positive lymph nodes) and 6 had associated ductal carcinoma in situ (DCIS). Ten phyllodes tumors contained osteosarcoma (OS), 2 contained chondrosarcoma (CS) and 2 were mixed. One phyllodes tumor also contained a no special type carcinoma component and one had associated DCIS. There were 15 pure OS or CS, and 2 mixed sarcomas (OS with CS or fibrosarcoma). No cases of sarcoma or phyllodes tumor had involved lymph nodes. IHC studies performed on 29 metaplastic carcinomas showed expression of keratin and p63. None of the 12 pure sarcomas studied by IHC showed any cytokeratin expression.
Conclusions: In the breast, OSD and CSD arise in 3 settings: a heterologous component of a metaplastic carcinoma, part of a malignant phyllodes tumor, or as pure sarcoma. IHC using antibodies to keratin and p63, as well as the presence of DCIS in adjacent ducts, assist in the recognition of metaplastic carcinoma. Phyllodes tumors with dominant sarcoma components are recognized by focal residual epithelial elements. Lymph node sampling is only useful in cases with no special type carcinoma components.
Category: Breast

Monday, March 19, 2012 1:00 PM

Poster Session II # 42, Monday Afternoon

 

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