Existence of MRI-negative clinical (large nerve) perineural squamous cell carcinoma spread.

To the Editor: As we are conducting research on perineural invasion of head and neck cancer in squamous cell carcinoma (SCC), we had great interest in reading the article by Jackson et al published online in Jan 2009. Although patients with microscopic perineural invasion of SCC (intermediate risk as per authors’ definition) had shown good local control rate at 5 years (84%), patients with clinical perineural invasions fared much worse (57%). Interestingly, within this group, patients who had radiologically positive disease did worse (38%) than those with radiologically negative disease (64%). This finding had been consistent with Galloway et al’s series by the group from the University of Florida. During our research, we have identified patients with symptoms such as paresthesia of trigeminal nerve resembling clinical perineural invasion following local excision. These patients had negative radiologic evidence of perineural invasion on MRI. Subsequent surgery involving resection of the same nerve causing paresthesia showed no perineural invasion. Therefore, it was plausible in these patients that symptoms of clinical perineural invasion, particularly with the trigeminal nerve, could result from the treatment of the primary cutaneous malignancy from the incision, rather than from disease invasion. Indeed, data published by the well-known group from the University of Florida had shown that patients who had clinically perineural-positive disease with negative radiologic evidence had outcomes comparable to the patients who had microscopic perineural disease in 2 separate studies (local control at 5 years: 76% vs 78%). While we acknowledge that the number of patients with clinical perineural invasion in this study was small and the authors had conducted subgroup analysis for radiologically negative patients, the inclusion of radiologically negative patients in the clinically perineural group could potentially lead to patients being counseled with higher cure rates than actually exist for true large nerve perineural spread.