[49] Diagnostic Value of aP2/FABP4 Expression in Soft Tissue Tumours

Takeshi G Kashima, Helen Turley, Arundhati Dongre, Francesco Pezzella, Nicholas A Athanaosu. Nuffield Orthopaedic Centre, University of Oxford, Oxford, United Kingdom; Oxford Radcliff Hospital, University of Oxford, Oxford, United Kingdom

Background: FABP4 (fatty acid-binding protein-4), also known as aP2 (adipocyte P2), is a fatty acid binding protein found in the cytoplasm of adipocytes. We have previously shown that aP2/FABP4 is useful in detecting lipoblasts using monoclonal and polyclonal antibodies. In this study, using a commercially available polyclonal antibody, we examined the diagnostic utility of aP2/FABP4 expression in a wide range of soft tissue tumours.
Design: Expression of aP2/FABP4 was determined by indirect immunoperoxidase immunohistochemical staining with the polyclonal antibody (Sigma, HPA002188), in paraffin sections of (formalin-fixed) normal adipose tissue and a wide range of soft tissue tumours.
Results: Fat cells in normal adipose tissue and lipomas (n=21) showed aP2/FABP4 expression around cytoplasmic fat. Some capillary endothelial cells also expressed aP2/FABP4, but fibroblasts, muscle and other cell types were negative. Other benign adipocytic tumours, hibernomas (n=3) and lipoblastomas (n=5) showed strong aP2/FABP4 staining of brown fat cells and lipoblasts respectively. Spindle cell lipomas (n=5) showed positive staining of fat cells but not spindle cells. In intermediate and malignant adipocytic tumours, the antibody labelled lipoblasts in atypical lipomatous tumour/well differentiated liposarcoma (n=26), myxoid/round cell liposarcoma (n=8) and pleomorphic liposarcoma (n=3). aP2/FABP4 expression was not seen in myxoid and other soft tissue tumours showing myxoid change containing (lipoblast-like) vacuolated cells including myxoma (n=10), low grade fibromyxoid sarcoma (n=2), myxofibrosarcoma (n=10), ossifying fibromyxoid tumour (n=2), leiomyosarcoma (n=2), rhabdomyosarcoma (n=3), solitary fibrous tumour (n=4) and chordoma (n=2).
Conclusions: aP2/FABP4 expression is seen in mature and immature fat cells. Expression of aP2/FABP4 aids in the identification of fat cells and lipoblasts in adipocytic tumours and is particularly useful in distinguishing myxoid/round cell and pleomorphic liposarcomas from myxoid (eg myxofibrosarcoma), spindle cell (eg leiomyosarcoma) and pleomorphic (eg rhabdomyosarcoma) sarcomas that contain vacuolated tumour cells which morphologically resemble lipoblasts.
Category: Bone & Soft Tissue

Monday, March 19, 2012 1:00 PM

Poster Session II # 32, Monday Afternoon


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