INK4-ARF and p53 mutations in metastatic cutaneous squamous cell carcinoma: case report and archival study on the use of Ink4a-ARF and p53 mutation analysis in identification of the corresponding primary tumor

So far, histopathologic, immunohistochemical and molecular properties of metastatic cutaneous squamous cell carcinomas (CSCCs) are relatively unexplored. In patients with multiple CSCCs, as for instance renal transplant recipients (RTRs), it might prove difficult to identify the primary tumor responsible for metastasis. We report a case of an RTR with multiple CSCCs, one of which metastasized. By using p53 and INK4a-ARF mutation analysis, we identified the responsible primary tumor due to an identical mutation in exon 2 of the INK4a-ARF locus. Archival study yielded 14 cases of metastatic CSCC (present case included). In only 8 of 14 metastases, DNA quality was sufficient to perform PCR reactions. In 7 of 8 metastases, either an INK4a-ARF (6 of 8 cases) and/or p53 (3 of 8 cases) mutation was present. In 6 of 7 cases, the corresponding primary could be identified by an identical mutation in p53 and/or INK4a-ARF. In conclusion, molecular analysis using a combination of p53 and INK4a-ARF mutation analysis can identify the corresponding primary skin tumor in case of CSCC metastases in the majority of cases. This is facilitated by the high frequency of these mutations in metastatic CSCC when compared with frequency spectra reported in the literature in primary CSCCs. The major limitation was formed by insufficient DNA quality in archival tissue.