Abstract
Introduction:
Solitary fibrous tumors (SFTs) are mesenchymal neoplasms associated with characteristic NAB2::STAT6 gene fusion. They frequently occur in extra-thoracic sites but are not uncommon in the head and neck (HN) region where 10–20% of all SFTs occur. Around 10% of HNSFTs recur, usually following incomplete resection. Myxoid SFT is a rare morphologic subtype of SFT, the features of which overlap with those of other myxoid-appearing tumors, making the diagnosis challenging.
Objective
To describe the distinctive histopathological and immunohistochemical features of myxoid SFT that aid in diagnosis
Materials and Methods
This 32-year-old male presented with a recurrent swelling in the nasal vestibule, which had previously been excised four years prior and diagnosed as neurofibroma. Examination revealed a firm swelling measuring 2x1cm.
Results
Histological examination showed a nodular tumor composed of short spindle shaped cells in an abundant myxoid stroma. Nuclei were ovoid, with minimal pleomorphism. Occasional intervening slender vascular channels were present; staghorn vasculature was absent. Tumor cells were diffusely immunopositive for STAT6, CD34 and Bcl-2, while S100, SOX10, EMA, ER and CD10 were negative, confirming the diagnosis of myxoid SFT.
Conclusion
Myxoid SFTs are unusual in the HN, with potential for misdiagnosis. Due to their propensity for local recurrence if incompletely excised, a high index of suspicion is required to include them in differential diagnosis of myxoid mesenchymal neoplasms occurring at this location. STAT6 is a reliable immunohistochemical marker that aids in diagnosis, reducing the necessity for molecular testing.