A Case of Metastatic Skin Cancer of the Right Hallux from Squamous Cell Carcinoma of the Lung

Abstract

A 75-year-old male noticed redness and swelling of the right hallux during chemotherapy for lung cancer. Antibiotics were administered by his primary doctor. His cutaneous symptoms initially improved ; however, they relapsed shortly afterwards, and he was referred to our department. At the rst visit, he had redness, swelling, and heat sensation in the right hallux. Whitlow was suspected and he was treated with intravenous antibiotics. Three weeks later, a bloody nodule was newly found on the right hallux. CT of the right foot showed osteolytic changes in the distal phalanx of the right thumb and a 38 mm large solid mass contiguous with the bone. Histopathology showed proliferation of tumor cells with nuclear atypia and mitotic gures. Immunohistochemically, the tumor cells were positive for both p40 and CK5/6. Based on these ndings, we made a diagnosis of skin metastasis from lung cancer to the right hallux. Although cutaneous metastasis of malignant tumors of the internal organs to the digits is very rare, lung cancer and esophageal cancer are frequently reported as primary lesions of metastasis. Our ndings suggest that it is necessary to differentiate metastatic skin tumor in patients presenting with possible paronychia or whitlow-like lesion. Skin Research, 22 : 24-29, 2023