Keratin 19-positive cutaneous squamous cell carcinoma with elevated serum cytokeratin 19 fragment 21-1 level: A case report

Cytokeratin 19 fragment 21-1 (CYFRA21-1) is a marker of lung cancer useful for evaluating clinical diagnosis and prognosis. To the best of our knowledge, there have been no reports of cutaneous squamous cell carcinoma (SCC) with high levels of CYFRA21-1 to date. We herein report a case of a 79-year-old man with a large subcutaneous tumor of the left shoulder, which was diagnosed as primary cutaneous poorly differentiated SCC. The tumor nests were composed of poorly differentiated atypical squamous cells exhibiting high-grade malignancy and mitotic figures; multinuclear cells were also identified inside lymph vessels. Keratin 19 (K19) was intensely expressed in tumor cells. A significantly elevated level of CYFRA21-1 (33 ng/ml) was observed preoperatively. After surgery, the level of CYFRA21-1 was significantly decreased (from 33 to 5.0 ng/ml). Our case demonstrated that K19-positive primary cutaneous undifferentiated SCC induced high levels of CYFRA21-1 in the serum. Thus, CYFRA 21-1 may be a marker indicative of poorly differentiated cutaneous SCC exhibiting K19 expression.