The benign skin masses, skin lesions, or benign skin tumors of the skin are common and do not usually lead to a significant clinical outcome. Initially, these lesions should be considered because some lesions are not known to be benign or because some malignant “malignant” lesions can resemble the benign lesions. Some benign lesions are actually benign at first and can turn into the malignant lesions after a while. Such lesions are also “premalignant”, that is, a lesion that can turn into the cancer. These lesions are described below with their names. For these reasons, the benign lesions should not be neglected, and they should be treated with a definitive diagnosis from the first complaints.
The benign skin lesions are classified in several different ways. For easy recall, the lesions will be classified under the different headings according to their etiology, anatomical structure and morphological features.
The benign skin lesions can be classified as 
1- Virus-induced skin masses
2- Epidermal tumors
3- Tumors of the skin appendages
4- Cystic lesions of the skin
5- Tumors of the mesodermal or soft tissue origin
6- Colored “Pigmented” lesions.
Meanings of words used in the definitions:
Macule: The flat and well-defined lesions
Papule: The lesions which are raised from the skin and usually smaller than 0.5 mm
Plaque: The lesions that are raised from the skin but whose surface is more than its height
Nodule: The lesions larger than the papules and raised from the skin
Pigmented Color
Epidermis: The upper thin layer of the skin
Dermis: The thick layer of the skin underneath
Lesion: The general name of the formations different from normal such as wounds and masses.
Premalignant Pre-cancerous
Excision Surgical removal
Nevus Mole

1- VIRUS-CAUSED SKIN MASSES
Verruca Vulgaris: These are the lesions that are caused by the human papilloma virus (HPV) and can be transmitted by the direct interpersonal contact or autoinoculation. They are most commonly seen in the hands, dorsal surfaces of the fingers and periungeal area. They are gray-white lesions with a rough surface, swelling from the surface epithelium, and varying in size from 0.1 to 1 cm. Histologically, the epidermal hyperplasia (acanthosis), hyperplasia of the keratin layer (hyperkeratosis) and koilocytosis due to the HPV are observed. In its treatment, the entire lesion should be curetted from the normal epidermis border. Apart from this, the use of the topical irritants, cryotherapy and laser ablation are other treatment options.
Condyloma Acuminatum: The papillary lesions formed by the effect of the HPV in the anogenital region are called condyloma acuminatum. It is usually observed in the preputial region and perianal region of uncircumcised men. It can cause ulceration and urethral fistula formation. Sometimes it can develop into the verrucous squamous cell cancer. The treatment is complete surgical removal of the mass.
Molluscum Contagiosum: It is a light colored, slightly raised papule, usually 2-5 mm in diameter, partially pitted in the middle, which develops due to the Poxvirus infection. After a while, it can reach to 1-2 cm in diameter and an inflammatory reaction, hyperkeratosis and secondary infection can develop around it. In this case, it can be compared to the skin cancer. The lesions can be carried by the hand smearing. It is mostly seen on the face, body, axilla and extremities. It can be seen in the genital area in the adults. Unlike other virus lesions, it is not seen on the palms and soles. Its characteristic feature is that the pit in the middle becomes deeper over time and takes the shape of a belly. The lesions do not overgrow and usually disappear spontaneously in 6-9 months. Histopathologically, the virus-infected epithelial cells are dark and round. It disperses easily with a light pressure.
The spontaneous recovery can be expected in the treatment or curettage, cryotherapy, electrocautery or the laser can be performed in the adults. The surgical excision is not recommended.
2- EPIDERMAL TUMORS
Keratoacanthoma: They are benign, self-limiting lesions that resemble squamous cell carcinoma clinically and histologically, observed in the sunlight-exposed areas. It is a premalignant lesion. It begins as an erythematous papule and reaches to 2 cm or larger in diameter by 2-8 weeks. The umbilicus in the middle is filled with the keratinous plaque. Over time, the plaque in the central part is removed and takes on a volcanic crater-like appearance. The lesion usually regresses spontaneously and heals with scarring. It is believed to originate from the pilar epithelium. When the lesion is first diagnosed, if it is completely excised when it is small, the treatment is provided. The differentiation from the skin cancer is provided by the biopsy.
Seborrheic Keratosis: The lesions seen in the elderly people, whose pigmentation and growth rate are directly related to the exposure to the sunlight. They are observed in the central parts of the body (chest, back, neck, face, scalp, proximal extremities). There is excessive keratin formation (hyperkeratosis) on their surface. The malignant transformation is not observed in these lesions. The curettage, shaving of the lesion from the skin surface, and introduction of the liquid nitrogen into the lesion are the methods used in the treatment.
Actinic Keratosis: It is the most common premalignant lesion on the skin. It is also called senile keratosis or solar keratosis. They are lesions that have erythematous borders scattered over the skin surface and can range in color from yellow to dark brown. Histologically, it contains a dense hyperkeratosis and sharply bordered areas of the parakeratosis. It usually occurs in the sun-exposed areas. The transformation into the squamous cell carcinoma is observed in up to 20% of the patients. The elliptic surgical excision can be applied in its treatment. Other than that, the liquid nitrogen, superficial curettage and electrocautery are acceptable treatment methods. The topical 5 fluorouracil can be used in very large lesions.
Cutaneous Horn: There is definitely another underlying pathology in these lesions. Usually the underlying pathology is the actinic keratosis. 10% of these lesions, which are not considered premalignant, are associated with the squamous cell carcinoma. It rarely arises from the basal cell carcinoma. It can also develop from the background of the keratoacanthoma, sebaceous adenoma and Kaposi's sarcoma. The treatment consists of the excision of the lesion with a 1-2 mm intact skin margin and treatment of the underlying pathology.
3- TUMORS OF SKIN ADNEXAL (Sweat gland, sebaceous gland, and hair root)
The tumors that develop from the hair root (follicles):
Pilomatrisoma (malherbe tm) are the solitary tumors observed on the face, neck or arm. Morphologically, it is in the form of a dermal nodule with a diameter of 0.5 cm. The treatment is the surgical excision.
             Trichoderma: It is observed as a single papule on the face. Multiple tricolemas can be seen in the Cowden syndrome.
             Trichoepithelioma: It begins as red papules 2-5 mm in diameter. It is more common in the nose, upper extremities and eyelids. The removal of the lesion is sufficient for its treatment.
The tumors that develop from the Sebaceous Glands:
Jadasson sebaceous nevus is present at birth and grows over time. In young patients, it has a smooth surface, yellow-brown color, and contains a small area of alopecia, while at puberty it thickens and acquires a varicose appearance. There is a possibility of malignancy in the future. It is a premalignant lesion. The prepubertal excision is the recommended treatment.
             Sebaceous adenoma is an angiofibromatous lesion and is not actually an adenoma. The presence of the multiple keratoacontomas with the multiple sebaceous adenomas is associated with the various internal malignancies and is characteristic of the Torre syndrome.
             Sebaceous Hyperplasia: It occurs in the middle age. The small, bright and white-yellow papules are the lesions that develop on the face.
Rhinophyma: It is the glandular form of the acne rosacea. It is not really a tumor, but its appearance and development are similar to the other skin tumors. It is characterized by the hypertrophy of the sebaceous glands in the skin covering the lower half of the nose, and the nose takes on a bulbous appearance. There is fibrosis, follicular plugs and fine vascular “telangiectasia” with the sebaceous hyperplasia on the nasal skin. Although the acne rosacea is 3 times more common in women, rhinophyma is 12 times more common in men than women. It has been reported that the risk of developing cancer from this background is 15-30%, and the basal cell cancer often develops. The most appropriate treatment is tangential excision.
Epidermal Nevus is an epidermal lesion characterized by the growth of superficial elements, epidermis, and skin appendage structures. It is also considered as a cutaneous hamartoma. It appears at birth or in early childhood. It is in the form of light or dark brown papules. There are also linear and verrucous forms. The diffuse epidermal nevi can be syndromic with the skeletal, ocular and central nervous system anomalies. It is more common in the leg and arm. The laser, cryotherapy and dermabrasion can be used for the treatment other than the surgical excision.
The tumors that develop from sweat glands:
Cylindrical (Turban tumor): It develops from the eccrine sweat glands during the puberty or later. It can be singly or multiple together. It is in the form of hard rubbery pink nodules. It is more common in the scalp and is treated by the surgical excision. It is a benign lesion, but the malignant change has been reported rarely.
Eccrine Poroma is a red, soft and often stalked, foot and sole lesions arising from the eccrine sweat glands at any age.
             Eccrine hydrocystoma is characterized by the multiple vesicular lesions. It is usually seen on the face of the elderly women, and temperature and sweating are the negative factors for the lesion.
             Syringoma develops from the eccrine sweat glands and is common in the puberty and women. They are the multiple vesicular lesions mostly seen on the face, eyelid, neck and upper thoracic wall. It has no malignant potential.

4- CYSTIC LESIONS OF THE SKIN
             Epithelial Cysts:
The epithelial cysts occur as a result of the occlusion of the pilosebaceous follicles or traumatic displacement of the epidermal cells into the dermis. The skin surface rises, and a punctum filled with keratin can be seen right next to it. Its treatment is excision to remove the entire epidermal remnant.
Pilar cysts:
They are the cysts originating from the outer root sheath of the hair follicle seen on the scalp. Its appearance is the same as epidermal cysts; the distinction can be made histologically. The treatment is excision.
Milia:
They are small superficial epidermal keratin cysts, usually 1-2 mm in size, seen on the face. It is considered to develop from the pilosebaceous follicles. The treatment is the removal of the contents with an incision made at the top of the lesion.
Dermoid cyst:
They are the congenital lesions located subcutaneously, usually in the lateral part of the eyebrow or in the medial canthal region of the midline (nasal midline). They are located at the embryological junction lines and are the lesions very close to or adjacent to the bone tissue. The treatment is excision.
5- TUMORS WITH THE MESODERMAL OR SOFT TISSUE ORIGIN
Leiomyoma is a tumor arising from the smooth muscle tissue. It is a benign tumor of the “erector pili” muscle located in the hair follicle of the skin. It can be found singly or in multiples. They are usually painful nodular erythematous masses. The surgical removal is the most appropriate treatment option.
Hemangiomas are the lesions that develop as a result of the vascular tissue (or endothelial) proliferation. They are present at birth or appear in the first 2-4 weeks after the birth. They mostly grow until the age of 2-4, and about 50-60% of them regresses spontaneously (by showing spontaneous regression) and disappears after this period. Those who do not show spontaneous regression are necessarily treated.
Lipoma develops from the adipose tissue or adipose cells. It can occur at any age and on any part of the body. The body is more common in the arms and legs. They are pale yellow, dirty yellow masses with the soft pseudo-encapsulated, non-adhesive to surrounding tissues. They are usually painless and slow growing masses. They are mostly located in the subcutaneous adipose tissue, but sometimes they are located in the different places such as the muscle. It can be painful when in the form of an angiolipoma.
Neurofibromas are the tumors that can occur at any age, consisting of the Schwan cells and endoneural fibroblasts. They are the masses of the medium hardness that are not tightly connected to the surrounding tissues. It is more common in the body, arms and legs. When they are more than one, it is usually called neurofibromatosis, and when it is accompanied by the brown spots, it is called Von Recklinghousen's syndrome, which is a hereditary disease.
Acrochordon (skin tag): They are the papillomatous lesions that begin in middle adulthood. It is observed on the neck, upper part of the trunk and axilla. It is numerous and is the same color as the skin. The large lesions can be stalked. The treatment is the superficial removal with the help of surgery.
Dermatofibroma: Dermatofibroma is a lesion usually observed as the papules or nodules on the extremities. It usually tends to be solitary and can be multiple in only 20% of the patients. The dermal papule, which tends to grow slowly and attaches to the overlying skin, can range in size from a few mm to 1-2 cm. There is a collapsed part in the middle. Sometimes the lesion is dark brown in color and can be confused with the malignant melanoma. The treatment is surgical removal.
Dermatofibrosarcoma Protuberans: It is a malignant fibrohistiocytic tumor that is not known exactly whether it spreads to the body or not. The subcutaneous fatty tissue can infiltrate the bone. These are lesions that tend to recur. It is more common in males in the third decade of life. It usually originates from the dermis tissue of the body and upper arm. It begins as a plaque-like nodular lesion fixed to the skin. It can move freely over the deep tissues. It has a color ranging from brown to red. Its treatment is very wide and deep excision. The patients should be followed up because of the possibility of recurrence.
Granular Cell Tumor: It is a tumor of unknown origin, which is thought to arise from the Schwann sheath of the nerve fiber. It is common in blacks in their 40s, 50s and 60s. 50% originates from the tongue; the remaining 50% originates from the head and neck. It is mainly located in the skin and subcutaneous tissue, but can be involved in the deeper tissues. There is a 3% risk of malignancy. The treatment is the surgical removal.
Infantile Digital Fibromatosis: 1/3 of the total lesions are present at birth and the remaining part occurs primarily in the hands and feet in the first year of life. As long as they do not cause the functional impairment and joint deformity, they do not cause complaints. There is a recurrence rate of 60% after the surgery. In order to reduce this possibility when surgically removed, it should be removed as a whole without leaving any tumor tissue behind.
6- PIGMENTED LESIONS
 A- Nevuses
The word nevus means spot or spot in Latin. It is a benign proliferation of the cells and is considered as a skin hamartoma. The word nevus usually refers to the melanocytic nevus. The melanocytes develop from the neural bud cells. The cells that leave the neural root during the development period in the mother's womb migrate and settle on the epidermal side of the dermo-epidermal junction. These cells produce the melanin pigment by giving the skin its color and protecting the skin from ultraviolet damage.
The melanocytic nevuses are divided into 3 groups.
- “Compound nevus”
- “Junctional nevus”
- “Intradermal nevus”
Furthermore, the nevuses are classified as congenital or acquired according to their occurrence.
The congenital giant hairy nevuses can occur all over the body, but usually occur on the head and buttocks. It carries a risk of 5-20% malignant changes throughout life. Therefore, it is recommended to remove them.
The acquired melanocytic nevuses typically appear between 6 and 12 months of life. They are usually less than 5 mm in diameter. Towards the age of 40, their number increases and then they begin to regress. If their numbers are high, the risk of the conversion to malignancy is higher.
The dysplastic or atypical nevus occurs at the puberty. They are larger than normal nevus. It has irregular borders and inhomogeneous pigmentation. They are more common in the closed areas of the body. The risk of developing into the malignant melanoma is quite high.
B- Special Nevuses
 Blue nevus (Blue nevus) occurs as a result of the accumulation of the melanocytic cells in the deep dermal tissue. It is blue, gray or blackish in color due to the deep settlement. It can be confused with the Malignant Melanoma. Rarely, it can become malignant. It is removed by the surgical excision and the definitive diagnosis is made and the treatment is done.
Spitz nevus is a melanocytic nevus mostly seen in the childhood. It manifests itself as a small pink nodule on the face or lower extremities. Its borders are clear and it has a distinct border that separates from the normal skin. It is of various colors and is higher than the skin. It is used to be called "juvenile melanoma" in the past. Histologically, the pleomorphic structure of the atypical cells draws attention. Sometimes it can be confused with the malignant melanoma.
Congenital Melanocytic Nevus is the nevus present at the birth and carries a risk of the malignancy in proportion to their size. Generally, they carry the risk of the malignant change in the period before the age of 9.
Atypical “junctional” melanocytic hyperplasia (Malignant Lentigo or Hutchinson's spot) is considered a precursor lesion of the malignant melanoma. It is like a dysplastic nevus but is lighter in color and has more irregular borders. When it is seen, the wide excision (with 5 mm of healthy tissue around) is recommended.
Becker Nevus is hairy and hyperpigmented lesion usually found on the chest, back and shoulders of men.
Ota Nevus is the nevus changing from blue to gray on the skin, mucous membranes and conjunctiva. It is present at birth and occurs in the area of the Trigeminus nerve distribution.
Ito nevus is the nevus of the ota that appear on the shoulders and neck.
Mongolian Spots are the hyperpigmented colored lesions found congenitally in the hip, coccyx, inguinal and genital (sacrococcygeal) areas. It usually disappears by itself when the child is 3-5 years old.
Spilus Nevus is in the irregularly shaped and light brown macula structure. The lesions are scattered dark macules and papules inside of it.
Labial Lentigo is the hyperpigmented macules that usually develop on the lips of women at a young age.
Epidermal Nevus (Linear nevus): It is actually an epidermal lesion and can be associated with the developmental anomalies. It appears at birth or in early childhood. It is in the form of light or dark brown linear papules. It is more common in the extremities. The laser, cryotherapy and dermabrasion can be used in the treatment other than the surgical excision.
Inflammatory Linear Verrucous Epidermal Nevus: It is similar to the epidermal nevus but in the form of erythematous, rough and scaly papules. It is also an epidermal lesion that appears at birth or in early childhood. They are itchy lesions and are more common in the extremities.