Approximately 5% of inflammatory or allergic sinonasal polyps develop extensive vascular proliferation and ectasia with deposition of pseudoamyloid. These so-called angiectatic nasal polyps (ANPs) can grow rapidly and exhibit an aggressive clinical behavior that could simulate malignancy preoperatively.
To systematically address the differential histologic diagnosis of ANPs.
We evaluated by light microscopy, immunohistochemistry, and electron microscopy biopsy and resection specimens from 2 large ANPs (8 and 10 cm in diameter) that presented in 2 adult men with life-threatening epistaxis and facial deformity, respectively.
The tumors were firm, lobulated, and covered by smooth, partially ulcerated mucosa. Histologically, clusters of dilated, thin-walled blood vessels embedded in pools of Congo red-negative eosinophilic material, associated with patchy necrosis and atypical stromal spindle cells, were seen. Electron microscopy and immunohistochemistry (CD34, factor VIII) confirmed the endothelial nature of the cells lining the spaces, whereas the atypical stromal cells were classified as myofibroblasts.
These 2 cases represent extreme examples of ANPs that clinically simulate a malignant process. Awareness of the histological features of ANPs should prevent confusion of such lesions with other vascular or spindle cell lesions of the nasopharynx that would require different treatment and carry a different prognosis.