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Squamous cell carcinomas of the facial skin metastasize preferable into the lymph nodes located in the area of the parotid gland. In a small part of the patients suffering from squamous cell carcinomas of the scalp loco-regional metastatic spread is observed. In long-term investigations their metastatic rate is given with up to 5% while squamous cell carcinomas of the auricle lead to a higher metastasis of up to 10%. Those rates are valid for immuno-competent patients suffering from untreated and non-advanced carcinomas. In comparison so-called high-risk carcinomas show a significantly higher metastatic rate. The metastatic affection of the parotid lymph nodes and their close contact to the cervical lymph nodes has a high prognostic relevance with a 5-year survival rate of only 25-50%.
From April 1998 to May 2009, 31 patients were diagnosed and treated for parotid metastasis of squamous cell carcinomas of the scalp at the Department of Otolaryngology, Head & Neck Surgery, of the University of Marburg, Germany. All cases were analysed retrospectively by means of a data entry form and they were evaluated with regard to anamnestic, clinical, imaging, and histologic findings concerning the primary tumor, the parotid and cervical metastases, therapy, and the course of the disease. All primary tumors were treated surgically and the diagnosis was histologically confirmed. The first diagnosis of the metastases in the area of the parotid gland occurred at an average of 11.8 months after diagnosis of the skin malignoma. Cervical metastases were found in 16 patients (52%). Distant metastasis could be confirmed in 7 patients (23%).
In the discussion of possible risk factors for metastatic spread, several factors could be revealed in the present study. The location of the carcinoma, its size of more than 1.5 cm, initially incomplete resection of the primary tumor, high age of the patient, and immuno-suppression were identified to be the main risk factors for development of parotid metastases.
Regarding the parotid metastases of squamous cell carcinomas of the scalp, they result from very aggressive tumors with early infiltrative growth and frequently extraparotid extent. Because of the close topographic relation to the cranio-jugular lymph nodes there is a high risk of involvement of the cervical lymph nodes which could be identified in 52% of the evaluated patients.
According to the data given in the literature, beside the size of the parotid metastasis (> 3 cm) the prognosis of patients with a parotid metastasis of a squamous cell carcinoma of the skin depends mainly on the extent of cervical metastatic spread. In the present study, a significant reduction of the mean survival rate to 14 months was due to the presence of cervical lymph node metastases. Patients without cervical lymph node metastases achieved a mean survival of 32 months. The mean survival of all evaluated patients amounted to 23 months.
Currently there are no randomized data on the improvement of the survival rate of patients suffering from high-risk carcinomas achieved by elective therapy of the parotid and cervical lymph nodes. For future investigations it is of high importance to analyse with regard to loco-regional metastasis if sentinel lymph node biopsy, elective neck dissection, or lateral parotidectomy may improve the tumor-free or total survival rate of patients with high-risk tumors.
According to the literature, the early diagnosis of parotid metastases in an early stage may significantly improve the prognosis of patients. The better prognosis of patients with small parotid metastases without cervical metastatic spread has already been mentioned. So the follow-up of high-risk patients has a high clinical and prognostic relevance. In high-risk patients ultrasound in narrow intervals is required for examination of the lymph nodes in the area of the parotid gland and the neck in order to early detect such metastases, especially during the first two years after initial diagnosis of the cutaneous carcinoma.
If parotid metastasis of a squamous cell carcinoma of the scalp is confirmed, the therapeutic concept including surgical resection of the parotid gland completed by cervical lymph node dissection and complete adjuvant irradiation is decisive for the therapeutic success. The importance of postoperative radiation could be confirmed by the results of the present study.