Hyalinizing spindle cell tumor with giant rosettes arising in the lung: report of a case with FUS-CREB3L2 fusion transcripts.

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). Lung involvement of HSCT is extremely rare, and only one case has been reported in the English-language literature. Reported herein is a case of primary pulmonary HSCT that had FUS-CREB3L2 fusion transcripts, a product of characteristic chromosomal abnormality t(7;16)(q33;p11) of HSCT and LGFMS. The patient was a 50-year-old woman who had a large solitary mass in the lung. 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-CREB3L2 fusion transcripts. Despite its bland morphology, it is known as low-grade sarcoma and its recognition in the lung would be helpful for accurate diagnosis and proper management of this rare tumor. RT-PCR for detection of FUS-CREB3L2 fusion transcripts is a useful method for differential diagnosis of primary pulmonary HSCT.