Zosteriform skin metastasis caused by retrograde lymphatic migration of metastatic squamous cell lung carcinoma

Background: Zosteriform skin metastasis (ZSM) is rare, and its etiology is not well understood. ZSM is possibly derived from the retrograde movement of cancer cells through the lymphatic vessels during disease development. However, it has been difficult to demonstrate it, as no specific findings have been observed. Case presentation: A 68-year-old man presented to our department with neck lymphadenopathy. After detailed examinations, squamous cell lung carcinoma (cT2aN3M1c) was diagnosed. Although cisplatin combined with gemcitabine was administered, his cancerous lymphangiopathy was exacerbated, and ZSM was observed on his right chest. Pembrolizumab was initiated as a second-line chemotherapy; however, the patient died 7 months after the initial presentation. In this case, fluorodeoxyglucose-positron emission tomography indicated the presence of skin metastasis and cancerous lymphangiopathy. Similarly, after performing an autopsy, tumor-cell filled lymph ducts were observed in the right subclavian and the cutaneous lymphatic vessel from the right hilar lymph nodes. Conclusions: To the best of our knowledge, this is the first study to demonstrate that the localization of ZSM in the cutaneous lymphatics was caused by the retrograde movement of cancer cells through the lymphatic vessels, using radiographical and pathological analysis. In addition, fluorodeoxyglucose-positron emission tomography may help predict skin metastasis induced by cancerous lymphangiopathy.