Leptomeningeal carcinomatosis from a recurrent cutaneous squamous cell carcinoma with perineural invasion in a lung transplant patient.

Leptomeningeal carcinomatosis occurs when tumor cells infiltrate the leptomeninges of the brain, spinal cord, and cerebrospinal fluid.1 Although seen with greater frequency in breast cancer, lung cancer, and malignant melanoma, it is extremely rare in cutaneous squamous cell carcinoma (CSCC). We present a case of recurrent CSCC with perineural invasion (PNI) that progressed to leptomeningeal carcinomatosis.