The primary differential was initially felt to be lymphoma, although some of the features were not typical (vessels encased rather than displaced, minimal enhancement). There was a history of latent tuberculosis in the family, but this was felt to be an unlikely cause for this presentation. Neuroblastoma was also considered. 

The degree of airway compression was critical on admission, and so the patient was started on steroids before biopsy. Further scans following this showed no change in the size of the mass, which meant the mass was unlikely to represent lymphoma. 

The patient underwent an ultrasound guided biopsy of the cervical component. The histology was reported as: "Specimen comprises a lesion comprising spindled cells with spindled collagen strands with prominent myxoid stroma. There are occasional foci with nuclear pallisading reminiscent of Verocay bodies. There is no significant mitotic activity or atypia. Immunohistochemistry shows that there is fairly diffuse positivity for S100 and CD34. There is focal positive staining for CD56 and Factor XIIIa. Calretinin staining is negative. Ki67 shows a proliferation rate of <1%. While the presence of Verocay body-like areas is noted, the overall morphologic features and immunophenotype are most in keeping with plexiform neurofibroma. There is no evidence of atypia or malignancy."

On examination the patient was noted to have multiple cafe-au-lait spots. Together with the plexiform neurofibroma, this was sufficient for a diagnosis of neurofibromatosis type 1.