Cutaneous metastases are rare, occurring in 5%-10% of patients with a cancer diagnosis, and only 0.8%-3.5% occur as the initial presenting sign of a malignancy. They occur more often in men, at an average age of 55 years, and typically present as multiple painless nodules near the primary malignancy site.

Nail unit or subungual metastases are extremely rare, representing only 0.1% of cutaneous metastases. Direct extension from a bony lesion under the nail plate is the most common etiology. A nail unit metastasis may be the first presentation of a malignancy.

In a review of 133 patients with nail unit metastases, the lung was the most common primary tumor site (41%), then the kidney (11%) and the breast (9%). Other reported primary sites are the head and neck, bone (sarcoma), gastrointestinal tract organs, and liver. Lung cancer was the main primary tumor for all digit metastases, and genitourinary tract tumors were most common for metastases in the toes. The fingers are involved in 90% of nail metastases, and the thumb is most commonly involved.