Lipomatous lesions show a broad morphological spectrum and clinically range from benign to highly malignant diseases. Over the last few years, studies focusing on lipomatous tumors have led to the delineation of new variants of lipomatous proliferations as well as to the introduction of new concepts, mainly as a result of the fruitful interactions between molecular genetics and pathology [1
]. As a result, chondroid lipoma has been described and considered a benign tumor of soft tissue that may mimic a variety of soft tissue tumors [1
At gross examination, chondroid lipoma resembles lipoma, presenting as a solitary, slowly growing mass that is located either within skeletal muscle, muscle fascia, or in the deep subcutis. The main cytological features consist of clustered, variably mature, multivacuolated hibernoma-like cells enmeshed in a capillary plexus, in a background of chondromyxoid material. This tumor may show histologic features resembling myoepithelioma, myxoid liposarcoma, extraskeletal myxoid chondrosarcoma, hibernoma, and other lipomatous or chondroid neoplasms, resulting in diagnostic and consequently therapeutic dilemmas [8
Cytogenetic data on a few cases of chondroid lipoma are available and show a balanced translocation t
(11;16) (q13-p12) [9
]. The typical and recurrent involvement of 11q13 has also been described in other classes of lipomatous tumors such as ordinary lipoma and hibernoma, but not in association with 16p12-13. Several genes at the breakpoint regions may be relevant candidate genes, and recently MKL/myocardin-like 2 (MKL2) has been implicated. Recent findings show that cyclinD1 (CCND1
) is not only involved in cell cycle regulation, but also in the regulation of cellular metabolism, cellular migration, and especially fat cell differentiation, making this a relevant candidate gene [12
]. Another candidate fusion gene is the FUS
gene located on chromosome 16p11. This gene is involved in one of the typical mimics of chondroid lipomas: myxoid liposarcoma. Although FUS
is located at a different chromosomal location (16p11 versus 16p12) and therefore involvement in chondroid lipomas is not highly likely, it has not been properly investigated.
Here, we describe a histopathological, immunohistochemical and fluorescence in situ hybridization analysis in a series of chondroid lipomas and histological mimics.