Molecular Particularity in Rare Tumour of Buttock: Case Report and Literature Review

Introduction: Hyalinizing spindle cell tumor with giant rosettes (HSCT) is a very uncommon mesenchymal tumor that has similar morphological and biological features to the low-grade fibromyxoid sarcoma (LGFMS). Case Report: Reported herein is a case of primary tumour of buttock HSCT that had rare FUS-CREB3L1 fusion transcripts, a product of characteristic chromosomal abnormality t (7, 16) (q33, p11) of HSCT and LGFMS. The patient was a 48-year-old man who had a large solitary mass in the buttock. Histologically, it was composed of bland spindle cells with variable cellularity deposited in a densely hyalinized stroma alternating with myxoid areas. Characteristic collagen rosettes were scattered in the cellular areas. Reverse transcription-polymerase chain reaction (RT-PCR) assay using formalin-fixed, paraffin-embedded tissue detected FUS-CREB3L1 fusion transcripts. In our knowledge is the second case may display a variant FUS/CREB3L1 fusion transcript in international literature. Conclusion: LGFMS and HSCT probably have a wider spectrum of morphologic features than previously thought, the awareness of which will help pathologists to avoid diagnostic pitfalls. Demonstration of the t (7, 16) translocation will help to diagnose difficult cases with unusual histologic features.