VASCULAR LESIONS
Bloody hell
Blood Blister - these are caused by trauma (eg, friction). Since it is filled with blood, you can infer that the dermis is damaged (no vessels in the epidermis). The epidermis is intact, and it serves as the roof of the blister. Blood blisters are relevant because they can mimic some vascular tumors.
Benign
Hemangioma - benign blood/lymph vessel tumor.
Strawberry Hemangiomas - a bold red plaque common in babies. They appear a few days after birth. Self-resolving after a few years
Cherry Hemangiomas - tiny red dots that occur in old people
Pyogenic Granuloma - benign vascular tumor. Sometimes the body wants to regenerate and grow (eg, pregnancy and trauma). The body accomplishes this growth by flooding itself with growth signaling molecules. The molecules circulate via the blood vessels, and so sometimes the blood vessels happen to get an extra-huge dose of growth signal. Vascular hyperplasia ensues. Visually, this looks like a blood blister. They bleed profusely, and so they’re often removed surgically. THERE’S NO PUS OR FEVER, THE NAME IS MISLEADING!
Cystic Hygroma - a newborn’s lymph vessel gets blocked, and the vessel swells (“grows”) up into a cyst. It’s a benign congenital malformation. Usually on the neck. Associated with Turner's (XO). It can cause a miscarriage.
Glomus Tumor - benign Glomus Bodies. Glomus Bodies are special SMCs that help to regulate temperature, and they’re found in the dermis of our digits. So the tumors will predictably appear at the tips of our fingers and toes (sometimes subungual). These tumors retain some of their original functions, and when exposed to extreme temperatures they become quite painful.
Malignant
Angiosarcoma - malignant blood/lymph vessels. Bad prognosis, but they’re thankfully rare. They look like nasty blood blisters. Chronic lymphedema is a common risk factor (eg, after radical mastectomy). (Angiosarcomas can also occur in the liver following vinyl / arsenic exposure, or in the breast after radiation therapy).
AIDS Defining
Kaposi Sarcoma - an AIDS defining lesion of the skin. It looks like numerous red/purple nodules. This cancer is caused by the HHV-8 virus (Human Herpesvirus 8). On biopsy, there will be numerous lymphocytes.
Bacillary Angiomatosis - another AIDS defining skin lesion. It looks like Kaposi Sarcoma (numerous red/purple nodules), but it’s actually caused by Bartonella, a bacterial infection of blood vessels in the skin transmitted from cats. It’s essentially a disseminated Cat Scratch Fever. And since it’s a bacterial infection, you can spot Neutrophils, which will help you differentiate it from Kaposi. Kaposi only causes skin symptoms, but BA causes fevers, malaise and lots of other general symptoms.
