Zosteriform and epidermotropic metastatic primary cutaneous squamous cell carcinoma

The first case of primary cutaneous squamous cell carcinoma (SCC) to cause zosteriform and epidermotropic metastasis to skin is reported. The patient is a 72-year-old Japanese woman. A cutaneous SCC appeared on the lateral side of her right knee and was removed. After dissection of the right inguinal lymph nodes, which revealed metastases, and irradiation of the right inguinal region, the patient presented with slightly pruritic and painful erythematous papules on the right hip and small brownish papules and vesicles with crusts on the anterior side of the right thigh. The eruptions were in a zosteriform distribution along the right L1 to L3 dermatomes. Histologically neoplastic squamous cell nests were observed in the epidermis, below the epidermal-dermal junction, and within lymphatic vessels in the deeper reticular dermis. We postulate that neoplastic cells with the ability to fuse with adjacent squamous epithelium may have been carried beneath the basal lamina or to the epidermis via dermal lymphatic backflow, resulting in epidermotropic metastasis.