What could cause an oval lump on your back below left shoulder blade?

There are several potential causes for an oval lump on your back below your left shoulder blade. Here are a few possibilities:

Lipoma: A lipoma is a slow-growing, benign tumor made of fat cells. Lipomas are typically soft, movable, and painless. They can occur anywhere on the body, including the back.

Muscle knot or strain: A muscle knot, also known as a trigger point, is a small, tight area of muscle that can cause pain and tenderness. Muscle knots can form in any muscle, including those in the back.

Cyst: A cyst is a closed sac filled with fluid or other material. Cysts can form anywhere on the body, including the back.

Swollen lymph node: Lymph nodes are small, bean-shaped glands that help filter bacteria and other foreign substances from the body. Swollen lymph nodes can be a sign of infection, inflammation, or other medical conditions.

Skin tag: A skin tag is a small, fleshy growth of skin that is attached to the body by a thin stalk. Skin tags are usually benign and painless, but they can sometimes become irritated or infected.

Birthmark: A birthmark is a mark on the skin that is present at birth. Birthmarks can vary in size, shape, and color. Most birthmarks are harmless, but some can be associated with medical conditions.

If you are concerned about a lump on your back, it's important to see a doctor for evaluation. The doctor can determine the cause of the lump and recommend treatment if necessary.