Cavernous hemangiomas (also called angioma cavernosum or cavernoma) are similar to strawberry hemangiomas but are more deeply situated. They may appear as a red-blue spongy mass of tissue filled with blood. Some of these lesions may disappear on their own -- usually as a child approaches school age.

In most cases, a health professional can diagnose a red birthmark based on the appearance of the skin. Deeper birthmarks can be confirmed with tests such as MRI, ultrasound, CT scans or biopsies. Read more about red birthmarks.