Lump in neck
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There is a large well circumscribed lesion located within the left carotid sheath displacing the internal carotid artery medially. The lesion is of low signal on T1 (similar to muscle) and high signal on T2 with a lower signal center giving it a target like appearance. It demonstrates vivid heterogeneous enhancement.
The patient went on to have the mass resected.
The core biopsy shows a proliferation of spindled stromal cells. They have elgonated nuclei with no significant nuclear pelomorphism. The cytoplasm is ill-defined. No mitoses or necrosis is seen. The background is loose and myxomatous with thin wavy bundles of collagen. The spindled cells are S-100 positive. They are synaptophysin, smooth muscle actin and CAM 5.2 negative. The features are those of benign peripheral never sheath tumour. The morphology is more suggestive of neurofibroma than schwannoma.
Left paraphyngeal mass: Benign peripheral nerve sheath tumour favouring neurofibroma.
Schwannomas are far more common in this region than neurofibromas, however both the histology and the imaging appearances (target appearance on T2 with peripheral high signal and lower central signal - thought to be due to a dense central area of collagenous stroma) favor a neurofibroma.