A 43-year-old female patient previously treated for a deep lobe parotid tumour measuring 26 mm in greatest diameter and with previous FNA diagnosed as a basal cell adenoma. A conservative partial parotidectomy was performed and definitive histology showed an adenoid cystic carcinoma pT2N0M0, with a variable histological pattern, mostly tubular with solid areas, others trabecular and few cribriform, with foci of perineural and intraneural invasion, contacting the surgical boundary.
In the case of involvement of positive or close surgical margins in adenoid cystic carcinoma after surgery, there is no standard approach; both margin widening and postoperative radiotherapy or margin widening followed by postoperative radiotherapy are valid3 . A PET-CT scan was performed, showing a slight metabolic increase at the parotid level without being able to rule out malignant disease. The patient was referred to the Maxillofacial Surgery Department and a total parotidectomy was performed together with excision of the zygomatic, buccal and marginal branches of the facial nerve, which were included in the tumour mass. Immediate reconstruction with sural nerve graft and filling of the post-parotidectomy defect with temporo-parietal fascial flap was performed. Intraoperative biopsies of the resected nerve endings were negative for neoplasia, definitive pathology of the parotidectomy demonstrated perineural and intraneural invasion adjacent to the tumour. Postoperative radiotherapy was administered because of the solid histological pattern, perineural invasion and margin involvement at the first surgery. During clinical follow-up, good resting function at eye closure and smiling was achieved, with only a slight deficit at blowing one year after surgery. An electroneurophysiological study was carried out 6 months and 1 year after the operation, the latter showing a quasi ad integrum restoration. The electroneurogram at 6 months showed an amplitude of 0.33 mV and a latency of 5.52 ms; and at one year the values were an amplitude of 1.6 mV and a latency of 2.85 ms. With regard to the electromyogram of both the orbicularis oculi and orbicularis labii muscles, denervation-reinervation data were observed with a greater number of polyphasic motor units at one year after the intervention.

