High resolution MRI of nail tumors and tumor-like conditions.

Although the nail is a small anatomical structure, it can be affected by various tumors and tumor-like conditions. Because of the distinctive nail anatomy, the clinical presentation of tumors is modified, thus rendering the diagnosis challenging. As nail biopsy and surgery are painful procedures associated with an increased risk of permanent onychodystrophy, pre-operative diagnosis is desirable. Although conventional radiographs are still the first-line radiologic examination for the assessment of bony structures beneath the nail matrix, they do not allow detailed evaluation of the phalangeal soft tissues. High resolution MRI allows accurate detection and mapping of nail lesions and can suggest a specific diagnosis. This review focuses on high resolution MRI of nail tumors and tumor-like lesions. We review the nail anatomy and the optimal MRI protocol. We then discuss a variety of tumors and tumor-like lesions in relation to the clinical presentation, anatomic location, histological features and imaging characteristics. We herewith describe common benign tumors (glomus tumor, onychomatricoma, keratoakanthoma, fibroma, subungual exostosis, hemangioma, chondroma, pyogenic granuloma), malignant tumors (subungual melanoma, subungual squamous cell carcinoma), as well as tumor mimics (mucoid cyst, epidermoid cyst). Although not entirely specific, MRI is a valuable tool in treatment planning of these tumors.