Late skip lymph node metastasis of oral squamous cell carcinoma or metastasis of unknown second primary tumor? Answer by mitochondrial DNA analysis

Patients with head and neck squamous cell carcinoma (SCC) are at risk of developing additional tumors in the head and neck. The detection of a late lymph node metastasis poses a problem to the clinician: it could be a delayed regional metastasis or a new metastasis from a yet unknown second primary tumor. Differentiation between metastasis and recurrence of primary tumors versus second primary tumor may be difficult because all lesions have the histologic appearance of SCC. Differentiation between these possibilities, however, carries important differences in therapeutic and prognostic consequences. In the following case report we present an unusually late regional lymph node metastasis in a patient who was treated 4 years earlier for an SCC in the inferior alveolar ridge. The purpose of the present study was to apply mitochondrial DNA D-loop analysis to assess the clonal relationship between oral tumor and node metastasis.