Spontaneous regression is seen in all except -a) Salmon patchb) Small Cavernous hemangiomac) Portwine staind) Strawberry angioma

**Core Concept**
Spontaneous regression refers to the natural resolution or disappearance of a condition without any treatment. In the context of vascular lesions, certain types of birthmarks are known to regress over time due to changes in hemodynamics or other factors.

**Why the Correct Answer is Right**
Spontaneous regression is a characteristic feature of small cavernous hemangiomas, which are benign vascular lesions composed of small, dilated blood vessels. These lesions are commonly seen on the skin and are known to regress over time due to the involution of the vascular channels. This process is thought to be mediated by the natural involution of the endothelial cells lining the blood vessels.

**Why Each Wrong Option is Incorrect**
**Option A:** Salmon patches are a type of birthmark that typically appear as pinkish-red macules on the face, particularly around the cheeks and nose. They are caused by the dilation of blood vessels and are not known to regress spontaneously.
**Option C:** Port-wine stains are a type of vascular birthmark that are caused by an abnormality in the formation of blood vessels. They are characterized by a persistent discoloration of the skin and do not regress spontaneously.
**Option D:** Strawberry angiomas, also known as infantile hemangiomas, are a type of benign vascular tumor that are commonly seen in infants. While they may regress spontaneously, they often require treatment to prevent complications.

**Clinical Pearl / High-Yield Fact**
It's essential to note that not all vascular lesions regress spontaneously, and some may require treatment to prevent complications. A thorough understanding of the natural history of these lesions is crucial for making accurate diagnoses and developing effective treatment plans.

**Correct Answer: B. Small Cavernous hemangioma**