Coexistence of neuroendocrine carcinoma and squamous cell carcinoma of the skin after kidney transplantation: a case report.

Neuroendocrine carcinoma (NEC) is a rare aggressive tumor of the skin with a shared phenotype of both endocrine and neuronal features. Its behavior includes rapid progression, common local recurrence, frequent metastasis to local lymph nodes, and occasional systematic involvement. The risk factors for NEC are similar to those for other skin cancers and mainly include ultraviolet light exposure, older age, T-cell immunosuppression, fair skin, and male sex. NEC is seen more frequently in the immunosuppressed population, and we report a rare case of NEC combined with squamous cell carcinoma (SCC) in a patient who underwent kidney transplantation. A 66-year-old man was referred with a brownish plaque on left cheek, and a punch biopsy result indicated SCC in situ. Wide excision was performed, and the defect was reconstructed using a bilobed flap. The final biopsy confirmed SCC combined with carcinoma with neuroendocrine differentiation, and positron emission tomography-computed tomography confirmed the absence of lymph node metastasis or systemic involvement. The patient showed no evidence of recurrence or other postoperative complications.