Perineural spread from head and neck tumors most commonly occurs with squamous cell carcinoma and adenoid cystic carcinoma. Perineural spread most commonly involves cranial nerve V (all three divisions may be involved) and may be retrograde (toward the brain) or anterograde (toward the orbit). Perineural tumor extension is also seen in lymphoma, melanoma, rhabdomyosarcoma, and malignant nerve sheath tumors. To know - CN VII is the second most common cranial nerve affected by perineural invasion. Ref: Ophthalmic Oncology edited by Bita Esmaeli, 2010, Page 359; Textbook of dermatologic surgery by Rusciani Robins, Luigi Rusciani, Perry Robins, Page 454.