Aims: To present eight cases of a distinctive morphological subtype of lipomatous tumour of soft tissue.
Methods and results: The clinicopathological, immunohistochemical and molecular pathological features of these tumours were analysed. The tumours were characterized by dense stromal sclerosis containing singly scattered pleomorphic atypical cells with lipoblastic features. The tumours occurred in four women and four men, aged 39-90 years (mean = 63). They were located in the retroperitoneum, thigh, retropubic space, arm and spermatic cord. Four cases arose de novo and four cases presented as local recurrences of previously resected liposarcomas. MDM2 amplification and cyclophosphamide doxorubicin hydrochloride (adriamycin), vincristine and prednisolone (CHOP) translocation was studied in seven cases by fluorescence in situ hybridization. High-level amplification of MDM2 at 12q13-15 was observed in 4/7 cases. All cases were negative for the CHOP translocation; in one MDM2+ case, the CHOP gene showed amplification but no translocation. Three patients died from their tumours from 1 to 6 years after their last surgery with lung metastases.
Conclusions: The tumours described appear to represent an unusual morphological variant of poorly differentiated liposarcoma associated with aggressive behaviour, and may represent a common end-stage pathway for various types of liposarcoma.