This glossary is a contribution made by Francisca Daza M.D. Department of Dermatology, Hospital Clinico U.Chile, University of Chile, Santiago, Chile
Abscess: A common infection characterized by a localized accumulation of polymorphonuclear leukocytes with tissue necrosis involving the dermis and subcutaneous tissue.
Acrochordon: Benign fleshy growth due to epidermal hyperplasia overlying a pedunculated papular dermal stalk. They are located preferentially in the flexures and on the neck of those over middle age.
Angiomas: Benign vascular tumor of the skin. Red to purple 1-3 mm circumscribed domed lesions scattered over the body surface. The first lesions typically appear by age 40, increasing in number subsequent to that. They are asymptomatic.
Angiokeratoma: A group of vascular ectasias that involve the papillary dermis and may produce papillomatosis, acanthosis, and hyperkeratosis of the epidermis. These lesions are most commonly found on the lower extremities as an asymptomatic solitary papule or plaque, but they can also be found in the upper extremities and the trunk. These lesions are of clinical importance because they may clinically mimic a malignant melanoma.
Angiokeratoma corporis diffusum (Fabry's disease): An x-linked recessive disease characterized by the deposition of ceramides within blood vessel walls. It is a lysosomal storage disease that is caused by deficient activity of lysosomal enzyme α -galactosidase A. Clinically it manifests with angiokeratomas on the thighs, scrotum or buttocks, although lesions can be anywhere. Other systemic manifestations are corneal dystrophy, acroparesthesias and vasomotor disturbances. Cardiac and renal disease is common, with death typically occurring by age 40.
Angiolymphoid hyperplasia with eosinophilia (ALHE): Uncommon idiopathic condition that manifests in adults as isolated or grouped papules, plaques, or nodules in the skin of the head and neck. Most patients present with lesions in the periauricular region, forehead, or scalp. Rare sites of involvement include the hands, shoulders, breasts, penis, oral mucosa, and orbit. This condition is marked by a proliferation of blood vessels with distinctive large endothelial cells. These blood vessels are accompanied by a characteristic inflammatory infiltrate that includes eosinophils. Whether ALHE represents a benign neoplasm or an unusual reaction to varied stimuli, including trauma, remains unclear.
Apocrine hidrocystoma: Apocrine hidrocystomas are benign cystic proliferations of the apocrine secretory glands. Most commonly appear as solitary, soft, dome-shaped, translucent papules or nodules and most frequently are located on the eyelids, especially the inner canthus. Apocrine hidrocystomas grow slowly and usually persist indefinitely.
Bacillary angiomatosis: A systemic disease caused by two Bartonella species, Bartonella henselae and Bartonella quintana. Most cases are concomitanta with AIDS. It appears as multiple subcutaneous nodules characterized histologically by a vascular proliferation. Skin lesions can resemble those seen in Kaposi's sarcoma.
Basal cell carcinoma: A nonmelanocytic skin cancer that arises from basal cells of the epidermis. It is a well demarcated, translucent papular or nodule with evident telangiectasia. There may be central ulceration, the so-called "rodent ulcer". Most commonly, they are localized in exposed to sun areas with significant actinic damage. Tumor size can vary from a few millimeters to several centimeters in diameter.
Cellulitis: A diffuse inflammation of connective tissue with severe inflammation of dermal and subcutaneous layers of the skin. Streptococcus is the commonest bacteria involved.
Chondrodermatitis Nodularis Helices: is a common, benign, painful papule of the helix or antihelix of the ear. Pain is experienced when sleeping. The exact cause is unknown, although most authorities believe it is caused by prolonged and excessive pressure.
Clear cell acanthoma: A benign tumor of the epidermis. Clinically it appears as a well marcated pink plaque/nodule, often with a scale. The characteristic, sharply demarcated edge shows a raised rim of keratin at the base.
Dermatofibroma: A common cutaneous nodule that consist of a benign proliferation of fibroblasts in association with an increased number of mast cells and, often, blood vessels. Clinically, the lesion is a tethered, firm, intracutaneous nodule of 0.5 to 2 cm in diameter, often with associated hyperpigmentation in the overlying skin. If rubbed, urtication from mast cell release of mediators can occur. Because of the tethering, squeezing the lesion results in a central umbilication, the dimple sign.
Elastosis perforans serpiginosum: Altered elastin, possibly secondary to a genetically determined defect, is extruded through the epidermis. Typically appearing in late childhood to early adulthood, keratotic papules with a horny plug occur in a serpiginous pattern. These rings of papules can expand peripherally, leaving atrophic skin in their wake. Typically, lesions occur on the sides and back of the neck. Many cases are associated with connective tissue syndromes such as Ehlers-Danlos syndrome, Marfan's syndrome, pseudoxanthoma elasticum and osteogenesis imperfecta. It has also been associated with Down's syndrome, and can occur in otherwise normal individuals. Drug induced causes include penicillamine.
Epidermoid cysts: cysts with an epithelial lining that contain keratin. The cyst begins as a nidus of epidermis below the epidermis. Keratin is produced, and with nowhere to be expelled, therefore the cyst slowly enlarges. As the epidermis grows over the cyst, the epidermis typically stretches, allowing the white to yellow color of the cyst to be evident. Cysts may become inflamed and resemble furuncles. Epidermoid cysts can occur sporadically, or as a part of a syndrome, such as Gardner’s syndrome.
Erythema elevatum diutinum: A rare type of leukocytoclastic vasculitis characterized by red, purple, brown, or yellow papules, plaques, or nodules. These lesions are usually distributed symmetrically on the extensor surfaces of the body. The etiology is unknown.
Erythema induratum (nodular vasculitis): Is considered a multifactorial syndrome of lobular panniculitis in which tuberculosis may be among the multiple causes. Clinically, it shows as persistent or recurrent ill-defined nodules that usually occur on the posterior calves of women. Nodules can develop irregular, shallow ulcers, often with a violaceous edge.
Erythema nodosum: An acute, nodular, erythematous eruption that usually is limited to the extensor aspects of the lower legs. Is presumed to be a hypersensitivity reaction and may occur in association with several systemic diseases or drug therapies, or it may be idiopathic. The inflammatory reaction occurs in the panniculus.
Fibrous papule of the nose: A solitary, firm, skin colored or pink papule occurring on the nose, less commonly elsewhere on the face. There is a distinct histological picture of fibrosis, ecstatic vessels and multinucleate cells of undetermined origin.
Glomus tumor: Benign lesions that typical present in young adults as small, blue-red papules or nodules of the distal extremities, with a predilection for subungual sites. Glomus tumors are typically painful, often causing paroxysmal pain in response to temperature changes or pressure. Glomus tumors are thought to arise from the glomus body, a thermoregulatory shunt concentrated in the fingers and toes. Two variants are noted: solitary glomus tumors and multiple glomus tumors, which are also known as glomangiomas or glomu-venous malformations.
Hemangiomas: Benign vascular neoplasms that have a characteristic clinical course marked by early proliferation and followed by spontaneous involution. During the proliferative phase in the neonatal period or early infancy, a rapidly dividing endothelial cell proliferation is responsible for the enlargement of infantile hemangiomas. Finally, an involutional phase occurs, whereby most infantile hemangiomas are clinically resolved by age 9 years.
Hematoma: A localized, tumor-like collection of blood.
Hidradenitis suppurativa: A chronic condition characterized by swollen, painful, inflamed lesions in the axillae, groin, and other parts of the body that contain apocrine glands. The disease is a chronic acneiform infection of the cutaneous apocrine glands that also can involve adjacent subcutaneous tissue and fascia. The hallmark of the disease is sinus tracts (which can become draining fistulas) in the apocrine gland body areas.
Juvenile xanthogranuloma: An idiopathic benign tumor of histiocytes. Usually asymptomatic; self-healing; red, yellow, or brown papules and nodules composed of histiocytic cells that predominantly occur in infancy and childhood. Papules or nodules occur in the skin, eyes, and viscera.
Kaposi's sarcoma: A neoplasm of proliferating blood vessels that often manifests with multiple vascular nodules in the skin and other organs.
Keratoacanthoma: A relatively common low-grade malignancy that originates in the pilosebaceous glands and pathologically resembles squamous cell carcinoma. It is characterized by a rapidly evolving tumor with a "volcano-like" appearance, rising sharply from the surrounding skin as a smooth edge tumor. Centrally, within the cone of the "volcano", is rough, keratotic tissue. Keratoacanthomas usually spontaneously resolve within eight weeks.
Leiomyoma: A benign tumor of smooth muscle usually derived from the erector pili muscle. A variant, angioleiomyoma, arises from the muscle of blood vessels. A leiomyoma typically is a round nodule less than 1 cm in diameter. Lesions may be painful. Secondary to contraction of the muscle elements, some lesions show evident clinical contraction associated with pain development.
Lipomas: Benign accumulations of fat cells. They are clinically seen as ill defined, soft, occasionally tender, masses in the subcutaneous tissue.
Lobular Capillary Hemangioma (Pyogenic granuloma): an exophytic vascular proliferation, usually in response to obvious trauma. The deep red to red-black nodule or polyp is typically 3-5 mm in diameter, although larger lesions can occur. Pyogenic granulomas are misnamed; they are neither infectious nor granulomatous.
Lymphangioma: Lymphangiomas are uncommon, hamartomatous, congenital malformations of the lymphatic system that involve the skin and subcutaneous tissues. The classification most frequently used divides these lesions into 2 major groups based on the depth and the size of these abnormal lymph vessels. The superficial vesicles are called lymphangioma circumscriptum. The more deep-seated group includes cavernous lymphangioma and cystic hygroma.
Lymphangioma circumscriptum: Consist of clusters of transparent to red vesicles and papules, resembling "frog spawn". There may be a lymphangioma (clear) and hemangioma (purple-red) component in a single lesion. Lesions commonly present in early childhood.
Melanoma: A malignant tumor of melanocytes. It accounts for only 4% of all skin cancers; however, it causes the greatest number of skin cancer related deaths worldwide. The development of melanoma is multifactorial and appears to be related to multiple risk factors, including fair complexion, excessive childhood sun exposure and blistering childhood sunburns, an increased number of common and dysplastic moles, a family history of melanoma, the presence of a changing mole or evolving lesion on the skin, and, importantly, older age. The most common warning sign for melanoma is a new or changing mole or blemish. Variation in color and/or an increase in diameter, height, or asymmetry of borders of a pigmented lesion are noted by more than 80% of patients with melanoma at the time of diagnosis.
Milia: Benign, keratin-filled cysts. Primary milia are typically seen in infants but also may occur in children and adults. Secondary milia are observed in a number of blistering disorders and following dermabrasion.
Molluscum contagiosum: A cutaneous eruption consisting of one or more, 1 to 3 mm. diameter, flesh colored papules with a central umbilication. It is caused by a member of the pox virus family.
Morphea (Localized scleroderma): A disorder characterized by excessive collagen deposition leading to thickening of the dermis, subcutaneous tissues, or both. Morphea is classified into plaque, generalized, linear, and deep subtypes according to the clinical presentation and depth of tissue involvement.
Neurofibroma: A neural tumor that can evolve from a papule to a nodule or polyp. These lesions can be single or multiple. When multiple, they may be indicative of the presence of neurofibromatosis. With direct pressure the lesion seems to "button hole" into the skin. Malignant transformation, while possible, is uncommon.
Pilomatrixoma: A pilomatrixoma is a benign appendageal tumor with differentiation toward hair cells. It usually manifests as a solitary, asymptomatic, firm nodule on the head. They are characterized by a lobular appearance and can be hard when palpated if there is extensive calcification within. It is more common in children, but occurrence in adults is increasingly being recognized. There may be an associated inflammation. Malignant transformation can occur, but is uncommon.
Pseudoxanthoma elasticum: An inherited disorder of connective tissue, characterized by abnormal elastotic fibers in the skin, blood vessels and eye. Both autosomal dominant and recessive variants show skin laxity, 1-3 mm yellowish papules involving the lateral aspect of the neck, upper trunk and elsewhere, and angioid streaks of the retina. Biopsy of the papules shows the characteristic elastotic change with calcium deposition.
Schwannoma: a tumor of the nerve sheath composed of Schwann cells. Typically firm 1-2 cm nodules on the head and neck of middle-aged individuals, these tumors are usually sporadic and solitary. When multiple, they are associated with an increased incidence of neurofibromatosis.
Sebaceous adenomas: Benign skin tumors that show histological differentiation towards sebaceous gland structures. Lesions of yellowish color that are usually 2 to 4 mm, but can reach 1cm in size.
Sebaceous carcinoma: Presents as a firm, usually yellowish, somewhat translucent nodule, most commonly on the face. Histologically, there is a malignant tumor with sebaceous differentiation. Metastases can occur.
Squamous carcinoma: A malignant tumor of epidermal keratinocytes. It frequently arises on the sun-exposed skin of middle-aged and elderly individuals. It is usually seen as an erythematous to skin-colored scaling plaque or nodule. Squamous carcinoma can also occur at the site of chronic irritation such as a chronic ulcer from any cause.
Syringoma: A benign adnexal neoplasm formed by well-differentiated ductal elements. They are skin-colored or yellowish, small, dermal papules. Usually multiple, arranged in clusters, and symmetrically distributed. Most commonly, syringomas are limited to the upper parts of the cheeks and lower eyelids.
Sclerosing hemangioma: (Pyogenic granuloma) is an exophytic vascular proliferation, usually in response to obvious trauma. The deep red to red-black nodule or polyp is typically 3-5 mm in diameter, although larger lesions can occur. Multiple grouped lesions can occur. Pyogenic granulomas grow rapidly over weeks.
Trichilemmal cyst: A scalp cyst containing keratin, with a cell wall histologically similar to the external hair root sheath. While often intracutaneous, lesions may become polypoidal. Asymptomatic lesions can become tender from trauma or secondary infection. The tendency to multiple lesions can be inherited as an autosomal dominant trait.
Trichoepitheliomas: Hamartomas with pilosebaceous differentiation. Clinically, these small, skin-colored papules can resemble milia, syringomas, or other benign skin tumors, in addition to nodular basal cell carcinomas.
Tuberous xanthomas: Yellow-orange nodules up to 2 cm in diameter, often located over knees and elbows in patients with hypercholesterolemia and other lipid abnormalities. All patients with tuberous xanthomas should have a lipid profile.
Xanthelasma: A soft, superficial, yellow-orange papule, most common on the medial upper eyelid. They are usually multiple and symmetrical in distribution. Although they are of considerable value in identifying hyperlipemic patients at risk for occlusive vascular disease, lesions can occur in normolipemic individuals.
Xanthomas: Lesions characterized by accumulations of lipid-laden macrophages, forming yellow-pink lesions visible to the eye. Xanthomas can develop in the setting of altered systemic lipid metabolism or as a result of local cell dysfunction.