A lesion is the general medical term used for a localized abnormality occurring in the structure of any tissue or organ in the body as a result of cellular damage, infection, inflammation, or abnormal growth. These cellular abnormalities may present with lesion symptoms such as redness, swelling, tissue loss, or pain depending on the anatomical region in which they are located. Trauma, genetic factors, bacterial and viral infections, and immune system problems are among the main causes of lesions. Depending on the nature of the detected tissue damage, its potential to be benign or malignant, and the organ in which it is located, personalized medication-based treatments, conventional surgery, or innovative non-surgical lesion treatment methods are planned. This loss of structural integrity in the body is one of the most fundamental clinical signs of a pathological process beginning at the cellular level.
What Is a Lesion?
When reading a medical report or reviewing an imaging result, one of the words most commonly encountered and generally most concerning is lesion. When this word is heard, the worst possible scenarios often immediately come to mind, but this is not always the case. Fundamentally, a lesion is not the direct name of a specific disease. It is an extremely broad and general medical term used to describe any physical change, injury, infection, or abnormal growth occurring in the structure of the body’s tissues or organs.
You can think of the human body as an enormous and complex factory operating flawlessly. When the functioning of any part of this factory is disrupted, damage occurs, or a foreign condition enters the system, the tissues respond. The visible form of this response, damage, or change, or the form detectable with radiological devices, is called a lesion. A simple redness suddenly appearing on the skin surface, an insect bite, or a bruise caused by impact is a lesion, just as a cystic structure developing deep within the liver or a small nodule in the lung is also called a lesion. What matters is accurately identifying the location, shape, and cause of this structural change and determining the appropriate course of action.
What Are the Types of Primary Lesions Seen on the Skin Surface?
The skin is the largest organ protecting the body against all dangers of the outside world. Because it is in direct contact with the external environment, it is the region that reacts most quickly and displays this reaction most clearly when an internal or external problem occurs. The first and direct structural abnormalities the skin develops in response to an agent are called primary skin lesions.
The most common types of primary skin lesions include:
- Bulla
- Macule
- Nodule
- Papule
- Plaque
- Pustule
- Vesicle
Explaining what these structures mean through their everyday equivalents makes the condition much easier to understand. A bulla is essentially the blistering that everyone knows and experiences from time to time. These large blisters, more than ten millimeters in diameter and completely filled with clear fluid, usually occur in severe burns, intense friction of the skin, or certain allergic reactions. A macule is a completely flat change in skin color that does not rise above the skin surface and cannot be felt with the fingertips when the eyes are closed. Sun freckles, flat moles, or the flat spots covering the skin in diseases such as measles have a macular structure.
The term nodule describes firm masses that extend into the deeper layers of the skin and underlying tissues. If a hard and distinct marble-like structure is felt beneath the skin on palpation, it is a nodule; subcutaneous fatty lumps are among the most common examples. A papule, unlike a macule, is a solid lesion smaller than ten millimeters that protrudes outward from the skin surface and contains no fluid. Warts and skin tags are classified as papules. A plaque forms when these papules merge to create much larger, flat-topped, thickened areas of skin; the broad, scaly, raised lesions caused by psoriasis are typical plaques. A pustule is an infected blister containing yellowish pus and inflammation, commonly referred to as a pimple in everyday language. A vesicle is a much smaller fluid-filled blister; the tiny fluid-filled sacs that appear along the edge of the lip during a cold sore are vesicles.
Which Secondary Skin Lesions Change Over Time?
Primary lesions do not always remain the same. Over time, as they are exposed to external factors, scratched by the patient, or altered by the body’s own healing efforts, cellular changes occur in these structures. The new structures that develop as a result of this progression are called secondary skin lesions.
The main examples of secondary skin lesions include:
- Atrophy
- Crust
- Erosion
- Ulcer
- Fissure
Atrophy is the thinning of the skin over time because of inadequate nourishment or excessive exposure to chemicals, causing it to become almost paper-thin and transparent and to lose its tissue volume and elasticity. Skin atrophy is frequently seen after years of incorrect corticosteroid cream use. A crust is the hard protective layer that forms when blood, tissue fluid, or inflammation leaking onto the surface of a wound comes into contact with air and dries; it functions as a natural biological bandage produced by the body to cover the wound. Erosion is the superficial loss of the uppermost layer of the skin as a result of friction or rupture of a blister, exposing the red tissue underneath.
An ulcer is an open wound that extends into the deeper layers of the skin and causes tissue loss, requiring greater medical attention and care. Healing is often difficult, and ulcers usually leave a visible scar after closure. Deep wounds that develop on the feet of patients with diabetes due to impaired circulation are among the best-known examples. Finally, a fissure is a thin, deep, and highly painful crack in the skin, particularly caused by excessive dryness, cold weather, or severe eczema.
Can a Lesion in the Body Be a Sign of Malignant Disease or Cancer?
The most critical issue concerning a lesion detected on the skin surface or in internal organs through advanced imaging methods is determining whether it is a benign and harmless structure or a malignant process containing cancer cells. Early detection of malignant lesions is life-saving because they may grow uncontrollably, invade the tissue in which they arise, and eventually spread to other organs.
If an existing skin lesion suddenly begins to grow rapidly, changes from having smooth circular borders to an irregular and asymmetrical shape, develops color changes, and particularly turns into a continuously bleeding open wound that fails to heal despite many months, this may be a strong sign of skin cancer. Malignant lesions developing in internal organs usually progress much more silently at first. Sudden and rapid weight loss without dieting or exercise, prolonged fatigue that does not improve with rest, unexplained internal bleeding, or firm masses palpable beneath the skin are important warning signs. In such suspicious cases, advanced imaging devices that perform molecular-level evaluation and visualize the high glucose uptake of tumor cells are used to clarify the nature of the lesion, followed by cellular confirmation.
Is a Lesion or Nodule Detected in the Lung Always Frightening?
Small, round opacities surrounded by clear air may be seen within the lung tissue on X-rays or CT scans performed because of symptoms or during routine health screening. In medical terminology, structures smaller than three centimeters in diameter are called solitary pulmonary nodules. If the lesion exceeds this size, it is no longer referred to as a nodule but as a mass, and its potential danger is considerably higher. However, seeing a lung nodule does not automatically mean that a person has cancer.
The vast majority of these incidentally detected nodules are actually harmless scars left behind by past conditions that may have gone unnoticed. Particularly in regions where diseases such as tuberculosis are common, previous lung infections may calcify over time and appear as nodules on CT scans. Benign lung structures known as hamartomas may also produce this appearance. If the CT examination shows popcorn-like calcifications within the nodule or very small surrounding spots known as satellite nodules, the lesion is considered highly likely to be completely benign. However, if the edges of the nodule are star-shaped and spiculated, if its calcification pattern is irregular, and especially if the nodule is larger than twenty-five millimeters, this may indicate a malignant process and requires further investigation.
Which Interventional Diagnostic Methods Are Used for a Suspicious Lung Lesion?
In individuals with a suspicious lung nodule, a risk profile is created by considering the lesion’s growth rate and the patient’s previous medical history. In low-risk cases, no needle-based or surgical intervention is required, and the size of the lesion is monitored through imaging at regular intervals. However, if the risk is calculated to be moderate or high, the cells within the lesion must be examined under a microscope through biopsy to reach a definitive decision.
These diagnostic procedures, which previously required opening the chest, can now be performed without large incisions using modern interventional radiology methods. During this procedure, performed under the guidance of computed tomography, the patient does not need to be placed under general anesthesia. Only the skin area where the needle will enter is numbed with local anesthesia. A very thin needle is then inserted through the skin and advanced under millimeter-by-millimeter CT guidance directly into the center of the target lung nodule. Small tissue samples obtained from the lesion are sent to the pathology laboratory. The procedure is completed by applying only a small adhesive bandage, and the patient can return to normal life within a short time. The rare occurrence of air leaking between the lung membranes after the procedure generally resolves spontaneously with rest. In addition, modern methods that search for tumor genetic material circulating in blood samples taken from the arm are emerging as promising developments that may support needle biopsy.
What Types of Cystic Lesions Are Detected in the Kidneys?
The kidneys are remarkable filtration systems that filter the blood and remove waste. As people age, cysts resembling small fluid-filled bubbles may form within these tissues. These cysts are generally discovered completely incidentally during ultrasound examinations performed because of abdominal pain or routine evaluation. Although most are harmless fluid-filled sacs, some kidney tumors may also develop in a cystic form, making accurate classification of these lesions very important. For this purpose, the Bosniak classification, based on radiological imaging and accepted worldwide as a standard, is used.
The stages of this frequently used classification system include:
- Bosniak Type One
- Bosniak Type Two
- Bosniak Type Two F
- Bosniak Type Three
- Bosniak Type Four
When examining the meaning of these categories, Type One and Type Two cysts are harmless cysts with walls as thin as paper, containing completely clear fluid without any solid clot or thick septum. They carry no risk of becoming cancerous and require neither follow-up nor surgery. Type Two F cysts are structurally somewhat more complex and contain very thin internal septa. Although the risk of cancer is low, they are usually monitored closely with annual imaging for five years to ensure stability. Type Three cysts are suspicious lesions with significantly thickened walls, irregular internal structures, and strong enhancement after intravenous contrast administration. Because their risk of malignancy is approximately fifty percent, they must be treated. Type Four cysts contain fleshy, solid tumor components within their walls, clearly exhibit malignant characteristics, and require intervention without delay.
What Non-Surgical Interventional Treatment Options Are Available for a Cystic Kidney Lesion?
The treatment applied to kidney cysts varies according to the structure of the lesion and the discomfort it causes the patient. Completely benign Type One or Type Two cysts may sometimes grow so large that they exceed ten centimeters, impair kidney function, or cause unbearable pain in the patient’s flank. In such cases, a non-surgical procedure is performed to collapse the cyst. A thin needle is inserted into the cyst under ultrasound guidance, and the fluid inside is completely drained. However, simply removing the fluid is not enough because the cyst will refill. To prevent this, chemical drying agents such as pure alcohol are injected into the cyst cavity to destroy the cyst wall. This allows the patient to be relieved of pain without any incision.
The situation is different for Type Three and Type Four cysts that carry a risk of malignancy or for small kidney tumors. In the past, the only option was surgical removal of a large part or all of the kidney, whereas today interventional ablation technologies are available. In tumors smaller than four centimeters, a thin probe is advanced through the patient’s skin directly into the center of the tumor under the guidance of specialized devices. Various energy sources are used either to heat the tumor internally to high temperatures or freeze it to extremely low temperatures, completely destroying the tumor cells. The patient’s organ remains in place while the tumor is successfully treated.
What Are the Types of Benign and Malignant Lesions Seen in the Liver?
The liver is essentially the body’s chemical factory and one of its most richly supplied organs. Within this intensive activity, various masses and lesions may occasionally develop. The most important stage in evaluating liver lesions is determining their precise nature.
The main types of lesions encountered in the liver include:
- Hemangioma
- Adenoma
- Focal Nodular Hyperplasia
- Hepatocellular Carcinoma
- Metastasis
To summarize these structures briefly, hemangiomas are the most common lesions in the liver and are completely benign structures consisting essentially of congenital tangles of blood vessels. Adenomas are benign masses generally associated with long-term use of birth control pills, but when they enlarge, they may carry a risk of bleeding or structural change. Focal nodular hyperplasia is also a harmless cellular growth that carries no risk. Among malignant lesions, hepatocellular carcinoma is the primary tumor of the liver that develops on a background of diseases such as cirrhosis. Metastases are malignant secondary tumors that form when cancer originating in another organ, such as the colon, lung, or breast, spreads through the bloodstream and settles in the liver.
How Does Interventional Radiology Contribute to the Treatment of Liver Lesions?
Interventional methods have revolutionized the treatment of liver lesions. For example, benign hemangiomas larger than five centimeters may rupture even after a minor blow to the abdomen and cause severe internal bleeding that threatens the patient’s life. Instead of open surgery, angiographic embolization methods are preferred in the treatment of these large vascular tangles. Very thin catheters are inserted through the groin and advanced directly to the main artery feeding the hemangioma, where a sclerosing medication is administered to permanently close the vascular mass from within. An important detail is that these vascular tangles, which are completely filled with blood, must never be treated with heat or burning procedures; otherwise, the destroyed blood cells may cause serious kidney damage.
Thermal ablation procedures are highly effective in treating cancerous liver lesions. In primary liver cancers, there is a tissue barrier surrounding the tumor that traps heat inside. Because the heat cannot escape, the tumor reaches extremely high temperatures as though it were inside an oven and is completely destroyed. However, this barrier is absent in metastatic lesions that have spread from another organ, and the surrounding blood flow may carry the heat away and cool the tumor. In such cases, chemoembolization, in which a high dose of chemotherapy is injected directly into the vessel feeding the tumor and the vessel is blocked, or radioembolization, in which radioactive particles are delivered into the tumor, can be successfully used to treat the lesions.
What Are the Types of Life-Threatening Lesions That Develop in the Brain Vessels?
The human brain requires an extraordinary amount of blood flow to function and is supplied by an extensive and highly complex vascular network. Within this delicate system, very serious vascular lesions carrying life-threatening risks may occasionally develop.
These critical problems affecting the brain vessels include:
- Brain Aneurysm
- Arteriovenous Malformation
- Ischemic Stroke
- Carotid Artery Stenosis
Explaining how these conditions develop provides a clearer understanding. A brain aneurysm occurs when the wall of a blood vessel weakens over the years because of factors such as high blood pressure or genetic predisposition and bulges outward like a balloon under the pressure of the blood flowing through it. It resembles a worn car tire developing a bulge and may cause a fatal brain hemorrhage if it suddenly ruptures. An arteriovenous malformation occurs when the arteries supplying the brain and the veins draining the blood become abnormally tangled together without forming a normal capillary network, creating a vascular mass that carries a constant risk of bleeding. Ischemic stroke occurs when a blood clot that has broken away from somewhere in the body suddenly blocks one of the major vessels supplying the brain. Because brain tissue is deprived of oxygen within minutes, sudden paralysis develops. Carotid artery stenosis is the dangerous reduction of blood flow caused by years of calcification and fatty plaque accumulation within the major vessels carrying oxygenated blood from the neck to the brain.
Which Non-Surgical Interventional Methods Are Used to Treat Lesions in the Brain Vessels?
In the past, treatment of lesions in the brain vessels required extremely long and risky brain surgeries in which the skull was opened. Today, thanks to the highly specialized field known as interventional neuroradiology, most of these problems can be treated entirely through minimally invasive, non-surgical methods without making any incision in the skull.
Procedures generally begin by entering the patient’s vascular system through the groin or wrist artery using extremely delicate tubes called catheters that are even thinner than a millimeter. These catheters are advanced through the blood vessels directly into the brain. If the patient has a brain aneurysm at risk of rupture, hair-thin platinum coils are delivered through the catheter and packed inside the aneurysm, preventing blood from entering it and completely eliminating the risk of rupture. In vascular malformations, the catheter is advanced to the center of the abnormal vascular tangle, where tissue-compatible medical adhesive substances are injected to solidify and permanently close the defective vessels from within. One of the most dramatic and life-saving situations is an acute stroke. When a clot blocks a brain vessel and the patient is experiencing paralysis, the patient is taken to the angiography unit. Very thin wire cages or high-suction vacuum catheters are used to capture the clot and remove it from the body. Once the vessel is reopened, the patient’s paralysis may begin to improve rapidly. In cases of narrowing in the neck arteries, protective filters are deployed to prevent clot migration, the narrowed area is expanded with a balloon, and metal mesh tubes known as stents are placed to keep the vessel open.
Which Interventional Ablation Procedures Are Used for Different Types of Lesions in the Body?
Ablation is the general name given to non-surgical treatments used to destroy benign lesions that have grown excessively and compress surrounding tissues, as well as cancerous tissues. These procedures are modern and safe medical technologies that spare the patient the difficulties of open surgery and are generally performed by numbing only the area where the procedure will be carried out.
The advanced ablation methods most frequently used in clinics to burn or freeze tumors include:
- Radiofrequency Ablation
- Microwave Ablation
- Cryoablation
- Irreversible Electroporation
- Chemical Ablation
The mechanisms of action of these methods are highly interesting. In radiofrequency ablation, electrical current delivered into the body causes ions in the target tissue to vibrate at extremely high speed. This intense vibration creates frictional energy, rapidly raising the temperature inside the tumor and causing the cancer cells to be destroyed by heat. Microwave ablation works according to the same principle as household microwave ovens; it rapidly vibrates the water molecules within the tissue, suddenly generating very high kinetic heat and destroying the tumor. Because it acts quickly, it is less affected by the cooling effect of nearby blood vessels.
Unlike heating methods, cryoablation is based on destroying tissue by freezing it. Special gases delivered through the tip of a needle rapidly lower the internal temperature of the tumor to approximately minus forty degrees Celsius. Ice crystals form inside the cancer cells, rupture their membranes, and kill them. The procedure is completely painless. Irreversible electroporation neither heats nor freezes the tissue. It delivers very high-voltage electrical pulses lasting only microseconds directly into the tumor. These shock waves create permanent nanoscale pores in the cancer cell membrane, causing the cell to collapse and die completely. Because no heat is used, it does not damage surrounding tissues in dangerous tumors attached to nerves or major blood vessels. Finally, chemical ablation is a procedure in which pure alcohol or similar substances are injected directly into relatively small and benign fluid-filled lesions through a needle, chemically destroying and drying out the affected area.
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