A mother brings her 3 month-old infant to the office with a red, vascular growth on the back. What is the most likely diagnosis?

The red, vascular growth described is most likely a hemangioma. Hemangiomas are benign tumors composed of a proliferation of blood vessels and commonly appear in infants, often in the first few months of life. They can present as raised, red lesions on the skin, typically on the head or neck, but can occur anywhere on the body.

These growths usually undergo a pattern of natural regression over time, often resolving by the age of 5 to 10 years. The presentation of a solitary red lesion in a young infant aligns well with the characteristics of a hemangioma, making this diagnosis appropriate.

In contrast, a pigmented nevus generally presents as a brown or black lesion and does not typically appear in the early months of life. A salmon patch, commonly known as an angel's kiss or stork bite, appears as a flat, pink mark and is also not raised or vascular in nature like a hemangioma. Malignant melanoma in an infant is exceedingly rare and would typically present with other concerning signs, which are not indicated in this scenario. Thus, the characteristics of the growth observed in this infant strongly suggest that it is a hemangioma.