Malignant solitary fibrous tumor of the temporal bone with NAB2 ex6::STAT6 ex16 fusion: a case report with literature review.

BACKGROUND

Malignant solitary fibrous tumor is a fibroblastic tumor with rare cases involving head and neck. We herein report a new case in a 73-year-old female patient with a lesion in the right temporal bone, along with a literature review.

CASE PRESENTATION: A 69-year-old female patient presented to the ENT clinic in 2021 with a three-week history of right-sided otalgia and hearing loss. Incisional biopsy was taken at that time and revealed reactive changes with no evidence of neoplasia. She was lost to follow up until she presented to the clinic again on 2025 with enlarging mass. CT imaging demonstrated a progressively enlarging lytic lesion in the right mastoid bone, measuring 5.5 by 3.0 cm while MRI revealed a large, destructive lesion centered in the right mastoid air cells, with both intra- and extracranial extension. Excisional biopsy was taken and showed cellular spindle cell proliferation arranged in short fascicles and storiform architecture with alternating hyper and hypocellular region with staghorn blood vessels. The lesion showed moderate cytologic atypia and a mitotic rate of 12 per 10 high-power fields (HPFs). Tumor cells were reactive for STAT6, BCL2, and CD99, while CD34 was negative. NGS showed NAB2 ex6::STAT6 ex16 fusion consistent with malignant solitary fibrous tumor. The patient was treated by adjuvant radiotherapy with no evidence of disease after 2 months.

CONCLUSION

We report a new case of malignant SFT with NAB2 ex6::STAT6 ex16 Fusion managed with surgery and adjuvant radiotherapy with no recurrence after 2 months. This case highlights the diagnostic challenges of SFT and the importance of continued case documentation to guide recognition of this rare entity.