O’Brien investigated neck metastases in a series of 242 patients with P+N0 disease. 110 Elective neck dissection of the cN0 can be selective based on the primary tumor site. 109 Parotidectomy and elective RT to the N0 neck is an option, with equivalent control shown to surgery and RT. If the rate of occult metastases to the neck is greater than the 20% threshold suggested by Weiss, elective neck dissection may be indicated. If facial paresis is present, then the nerve should be resected in the course of a radical parotidectomy with consideration of FS control of the proximal facial nerve stump.
Parotid metastases not involving the facial nerve should be treated with a therapeutic superficial or total parotidectomy depending on the clinical and radiographic evidence of involvement of the deep lobe. If the result is still nondiagnostic, a lymph node biopsy within an access incision, placed with mindfulness of the possibility of later surgery, is indicated. 108 A nondiagnostic result should prompt repeat testing, which, if a cytologist is present in the clinic, incurs no delay. The confirmation of metastatic cutaneous SCC in the parotid or neck is usually initially by needle aspiration cytology, preferably ultrasound guided, which has a specificity of 98%. 107 Disease staged as P1N0 ( Table 42.5) have an overall 5-year survival rate of 65–70%, reducing to 30% with N2 disease. 106 Patients with involved parotid nodes have a high incidence of clinical (26%) or occult (35%) neck metastases, which correlates with 5-year survival. O’Brien suggested a staging system for metastatic cutaneous SCCs based on involvement of the parotid. 105 Positive margins and local recurrence are also risk factors. 103 The seventh edition of the staging classification by the American Joint Committee on Cancer (AJCC) incorporates these additional risk factors in the T-staging of cutaneous SCC, including the 2-mm cutoff.
103,104 It is suggested that given the thin skin of the face, SCCs at this anatomic site merit the lower thickness threshold of 2 mm. 101,102 SCCs are considered high risk when they are greater than 2 cm in maximum diameter (three times more likely to metastasize), are greater than 4 mm thick, involve the subdermal fat, are poorly differentiated or of histologic desmoplastic subtype, or show perineural and/or lymphovascular invasion, or when the patient is receiving immunosuppressant therapy. Overall 5% of cutaneous SCCs will metastasize, but the rate increases to over 20% for those involving the scalp, external ear, temple, and periocular region. Metastatic basal cell carcinomas are exceedingly rare and arise from neglected giant basal cell carcinomas (BCC) or the basosquamous subtype. SCC, malignant melanoma, and Merkel cell tumors are the most common skin malignancies that affect the parotid. Cutaneous malignancy of these areas can manifest with parotid lymph node metastasis, often with features of aggressiveness such as fixity, skin ulceration, facial nerve weakness, and concurrent cervical metastases. The parotid lymph nodes are frequently the first-echelon nodes to the skin of the ear, cheek, temple, forehead, and anterior scalp. David Tighe, in Oral, Head and Neck Oncology and Reconstructive Surgery, 2018 Surgical Management of the Parotid and Neck for Metastatic Cutaneous Malignancy