Dermoscopy is a noninvasive technique utilizing a handheld magnifying device coupled with a transilluminating lift. It is often used in the evaluation of cutaneous lesions, but lacks the definitive diagnostic ability of biopsy-based tissue diagnosis. Histopathologic exam remains the gold standard

A lesion biopsy is performed if the diagnosis remains uncertain after a clinical physical exam. The most common tissue sampling techniques include shave or punch biopsy. When only a portion of the lesion can be removed due to its size or location, the biopsy should sample tissue from the thickest area of the lesion, as SCCs are most likely to be detected in that area. If a shave biopsy is performed, it should extend through to the level of the dermis in order to provide sufficient tissue for diagnosis; ideally, it would extend to the mid-reticular dermis. Punch biopsy usually extends to the subcutaneous fat when the entire length of the punch blade is utilized.

The disease often goes undiagnosed for several years, as it is sometimes not recognized and misdiagnosed as thrush or other problems and not correctly diagnosed until the patient is referred to a specialist when the problem does not clear up.

A biopsy of the affected skin can be done to confirm diagnosis. When a biopsy is done, hyperkeratosis, atrophic epidermis, sclerosis of dermis and lymphocyte activity in dermis are histological findings associated with LS. The biopsies are also checked for signs of dysplasia.

It has been noted that clinical diagnosis of LS can be "almost unmistakable" and therefore a biopsy may not be necessary.

Lichen planus has a unique microscopic appearance that is similar between cutaneous, mucosal and oral. A Periodic acid-Schiff stain of the biopsy may be used to visualise the specimen. Histological features seen include:

- thickening of the stratum corneum both with nuclei present (parakeratosis) and without (orthokeratosis). Parakeratosis is more common in oral variants of lichen planus.

- thickening of the stratum granulosum

- thickening of the stratum spinosum (acanthosis) with formation of colloid bodies (also known as Civatte bodies, Sabouraud bodies) that may stretch down to the lamina propria.

- liquefactive degeneration of the stratum basale, with separation from the underlying lamina propria, as a result of desmosome loss, creating small spaces (Max Joseph spaces).

- Infiltration of T cells in a band-like pattern into the dermis "hugging" the basal layer.

- Development of a "saw-tooth" appearance of the rete pegs, which is much more common in non-oral forms of lichen planus.

Lichen planus lesions are diagnosed clinically by their "lichen-like" appearance. A biopsy can be used to rule out conditions that may resemble lichen planus, and can pick up any secondary malignancies.

Discontinuing contact with the heat source is the initial treatment of erythema ab igne. If the area is only mildly affected with slight redness, the condition may resolve itself in a few months. If the condition is severe and the skin pigmented and atrophic, resolution is unlikely. In this case, there is a possibility that a squamous cell carcinoma or a neuroendocrine carcinoma such as a Merkel cell carcinoma may form. If there is a persistent sore that does not heal or a growing lump within the rash, a skin biopsy should be performed to rule out the possibility of skin cancer. If the erythema ab igne lesions demonstrate pre-cancerous changes, the use of 5-fluorouracil cream has been recommended. Abnormally pigmented skin may persist for years. Treatment with topical tretinoin or laser may improve the appearance.

The disease can last for a considerably long time. Occasionally, "spontaneous cure" may ensue, particularly in young girls.

Lichen sclerosus is associated with a higher risk of cancer. Skin that has been scarred as a result of lichen sclerosus is more likely to develop skin cancer. Women with lichen sclerosus may develop vulvar carcinoma. Lichen sclerosus is associated with 3–7% of all cases of vulvar squamous cell carcinoma. In women, it has been reported that 33.6 times higher vulvar cancer risk is associated with LS. A study in men reported that "The reported incidence of penile carcinoma in patients with BXO is 2.6–5.8%".

In 2015, an Italian team of scientists, led by Michele De Luca at the University of Modena, successfully treated a seven-year-old Syrian boy who had lost 80% of his skin. The boy's family had fled Syria for Germany in 2013. Upon seeking treatment in Germany, he had lost the epidermis from almost his entire body, with only his head and a patch on his left leg remaining. The group of Italian scientists had previously pioneered a technique to regenerate healthy skin in the laboratory. They used this treatment on the boy by taking a sample from his remaining healthy skin and then genetically modifying the skin cells, using a virus to deliver a healthy version of the LAMB3 gene into the nuclei. The patient underwent two operations in autumn 2015, where the new epidermis was attached. The graft had integrated into the lower layers of skin within a month, curing the boy. The introduction of genetic changes could increase the chances of skin cancer in other patients, but if the treatment is deemed safe in the long term, scientists believe the approach could be used to treat other skin disorders.

CGPD is known to be a temporary skin disease with a benign course. The skin papules typically resolve after a few months to a few years. After CGPD resolves, the skin may return to normal without scarring or may have small atrophic depressions with collagen loss, milia, or small pit-like scars.

These include:

- "Generalized atrophic benign epidermolysis bullosa" is a skin condition that is characterized by onset at birth, generalized blisters and atrophy, mucosal involvement, and thickened, dystrophic, or absent nails.

- "Mitis junctional epidermolysis bullosa" (also known as "Nonlethal junctional epidermolysis bullosa") is a skin condition characterized by scalp and nail lesions, also associated with periorificial nonhealing erosions. Mitis junctional epidermolysis bullosa is most commonly seen in children between the ages of 4 and 10 years old.

- "Cicatricial junctional epidermolysis bullosa" is a skin condition characterized by blisters that heal with scarring. It was characterized in 1985.

Oral antibiotics of the tetracycline class such as minocycline, doxycycline, and tetracycline have been recommended for CGPD. However, their use is limited by side effects such as nausea, vomiting, and sensitivity of the skin to sunlight. Tetracycline antibiotics are not recommended for children under the age of 8 since tetracyclines are known to deposit in teeth (thereby staining them) and impair bone growth in children. The use of calcineurin inhibitor creams such as tacrolimus or pimecrolimus on the skin is controversial and results have been mixed. Certain studies have found the use of topical calcineurin inhibitors led to resolution of CGPD whereas others found incomplete resolution or prolonged symptoms. Topical azelaic acid has also been used successfully to treat CGPD.

The differential diagnosis includes oral lichen planus, erythematous candidiasis, leukoplakia, lupus erythematosus, glossitis, and chemical burns. Atrophic glossitis is usually distinguished from benign migratory glossitis on the basis of the migrating pattern of the lesions and the presence of a whitish border, features which are not present in atrophic glossitis, which instead shows lesions which enlarge rather than migrate. Rarely, blood tests may be required to distinguish from glossitis associated with anemia or other nutritional deficiencies. Since the appearance and the history of the condition (i.e. migrating areas of depapillation) are so striking, there is rarely any need for biopsy. When biopsy is taken, the histopathologic appearance is quite similar to psoriasis:

- Hyperparakeratosis.

- Acanthosis.

- Subepithelial T lymphocyte inflammatory infiltrate.

- Migration of neutrophilic granulocytes into the epithelial layer, which may create superficial microabscesses, similar to the Munro's microabscesses described in pustular psoriasis.

Clinical evaluation and identification of characteristics papules may allow a dermatologist to diagnose Degos disease. The papules have a white center and are bordered with a red ring. After lesions begin to appear, the diagnosis for Degos disease can be supported by histological findings. Most cases will show a wedge-shaped connective tissue necoris in the deep corium. This shape is due to the blockage/occlusion of small arteries.

Individuals may be diagnosed with the benign form if only the papules are present. However, an individual may be diagnosed with the malignant form if involvement of other organs like the lungs, intestine and/or central nervous system occurs. The malignant, or systematic form of this condition may suddenly develop even after having papules present for several years. In order to quickly diagnose this shift to the malignant variant of the disease, it is important for individuals to have consistent follow-up evaluations.In these evaluations, depending on which organs are suspected to be involved, the following procedures and tests may be conducted: skin inspection, brain magnetic resonance tomography, colonoscopy, chest X-ray, and/or abdominal ultrasound.

PVA usually has an underlying cause, attributed to existing skin diseases and disorders associated with a cutaneous lymphoma or inflammation. Mycosis fungoides is the common lymphoma believed to cause PVA, although it may be considered a precursor when the lymphoma is (hidden) and undiagnosed. Large plaque parapsoriasis is another common causes of PVA. Less common causes include autoimmune-related connective tissue diseases such as lupus, dermatomyositis and scleroderma. Dermatoses and those that are genetically inspired, called genodermatoses, may also be an underlying cause of PVA. Among them, xeroderma pigmentosum and Rothmund-Thomson syndrome (poikiloderma congenita) are thought to be the most prominent. Ingestion of substances containing arsenic, such as arsphenamine, has also been suggested as a least common cause. PVA can also be idiopathic (of unknown cause), as seen in a small number of cases.

Erythema ab igne was once commonly seen in the elderly who stood or sat closely to open fires or electric heaters; however, erythema ab igne has been reported in both young and elderly individuals. Women have a higher incidence of erythema ab igne than men. Although wide use of central heating has reduced the overall incidence of erythema ab igne, it is still sometimes found in people exposed to heat from other sources such as heating pads, space heaters, hot water bottles, and electronic devices.

Many conditions affect the human integumentary system—the organ system covering the entire surface of the body and composed of skin, hair, nails, and related muscle and glands. The major function of this system is as a barrier against the external environment. The skin weighs an average of four kilograms, covers an area of two square meters, and is made of three distinct layers: the epidermis, dermis, and subcutaneous tissue. The two main types of human skin are: glabrous skin, the hairless skin on the palms and soles (also referred to as the "palmoplantar" surfaces), and hair-bearing skin. Within the latter type, the hairs occur in structures called pilosebaceous units, each with hair follicle, sebaceous gland, and associated arrector pili muscle. In the embryo, the epidermis, hair, and glands form from the ectoderm, which is chemically influenced by the underlying mesoderm that forms the dermis and subcutaneous tissues.

The epidermis is the most superficial layer of skin, a squamous epithelium with several strata: the stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale. Nourishment is provided to these layers by diffusion from the dermis, since the epidermis is without direct blood supply. The epidermis contains four cell types: keratinocytes, melanocytes, Langerhans cells, and Merkel cells. Of these, keratinocytes are the major component, constituting roughly 95 percent of the epidermis. This stratified squamous epithelium is maintained by cell division within the stratum basale, in which differentiating cells slowly displace outwards through the stratum spinosum to the stratum corneum, where cells are continually shed from the surface. In normal skin, the rate of production equals the rate of loss; about two weeks are needed for a cell to migrate from the basal cell layer to the top of the granular cell layer, and an additional two weeks to cross the stratum corneum.

The dermis is the layer of skin between the epidermis and subcutaneous tissue, and comprises two sections, the papillary dermis and the reticular dermis. The superficial papillary dermis with the overlying rete ridges of the epidermis, between which the two layers interact through the basement membrane zone. Structural components of the dermis are collagen, elastic fibers, and ground substance. Within these components are the pilosebaceous units, arrector pili muscles, and the eccrine and apocrine glands. The dermis contains two vascular networks that run parallel to the skin surface—one superficial and one deep plexus—which are connected by vertical communicating vessels. The function of blood vessels within the dermis is fourfold: to supply nutrition, to regulate temperature, to modulate inflammation, and to participate in wound healing.

The subcutaneous tissue is a layer of fat between the dermis and underlying fascia. This tissue may be further divided into two components, the actual fatty layer, or panniculus adiposus, and a deeper vestigial layer of muscle, the panniculus carnosus. The main cellular component of this tissue is the adipocyte, or fat cell. The structure of this tissue is composed of septal (i.e. linear strands) and lobular compartments, which differ in microscopic appearance. Functionally, the subcutaneous fat insulates the body, absorbs trauma, and serves as a reserve energy source.

Conditions of the human integumentary system constitute a broad spectrum of diseases, also known as dermatoses, as well as many nonpathologic states (like, in certain circumstances, melanonychia and racquet nails). While only a small number of skin diseases account for most visits to the physician, thousands of skin conditions have been described. Classification of these conditions often presents many nosological challenges, since underlying etiologies and pathogenetics are often not known. Therefore, most current textbooks present a classification based on location (for example, conditions of the mucous membrane), morphology (chronic blistering conditions), etiology (skin conditions resulting from physical factors), and so on. Clinically, the diagnosis of any particular skin condition is made by gathering pertinent information regarding the presenting skin lesion(s), including the location (such as arms, head, legs), symptoms (pruritus, pain), duration (acute or chronic), arrangement (solitary, generalized, annular, linear), morphology (macules, papules, vesicles), and color (red, blue, brown, black, white, yellow). Diagnosis of many conditions often also requires a skin biopsy which yields histologic information that can be correlated with the clinical presentation and any laboratory data.

The diagnosis is usually made on the clinical appearance, and tissue biopsy is not usually needed. The histologic picture is one of superficial candidal hyphal infiltration and a polymorphonuclear leukocytic inflammatory infiltrate present in the epithelium. The rete ridges are elongated and hyperplastic (pseudoepitheliomatous hyperplasia, which may be mistaken for carcinoma).

The condition may disappear over time, but it is impossible to predict if or when this may happen.

The most common treatment is the acne medication isotretinoin. It may be combined with prednisone. Dapsone, which is normally used to treat leprosy, is a riskier medication but is sometimes prescribed in cases where the normal therapy is ineffectual. Antibiotics such as tetracycline or erythromycin may also be prescribed. An alternative option is to treat with carbon dioxide laser therapy, followed by topical tretinoin therapy.

Surgery may be necessary to remove large nodules. Alternatively, nodules can be injected with corticosteroids such as triamcinolone.

Actinic granuloma (also known as "O'Brien granuloma") is a cutaneous condition characterized histologically by a dermal infiltrate of macrophages.

Actinic granuloma is an asymptomatic granulomatous reaction that affects sun-exposed skin, most commonly on the face, neck, and scalp.

It is characterized by annular or polycyclic lesions that slowly expand centrifugally and have an erythematous elevated edge and a hypopigmented, atrophic center.

Advise to reduce exposure to the sun and to use sunscreen.

Treatment with topical halometasone cream, pimecrolimus cream.

The cause is unknown but is thought to be associated with diabetic neuropathy and vascular complications; because the lesions are more common on the shins, some suggest it represents an altered response to injury. It is seen more commonly in patients with longstanding diabetes and poor glucose control.

Rombo syndrome is a very rare genetic disorder characterized mainly by atrophoderma vermiculatum of the face, multiple milia, telangiectases, acral erythema, peripheral vasodilation with cyanosis and a propensity to develop basal cell carcinomas.

The lesions become visible in late childhood, began at ages 7 to 10 years and are most pronounced on the face, At that time a pronounced, somewhat cyanotic redness of the lips and hands was evident as well as moderate follicular atrophy of the skin on the cheeks. In adulthood, whitish-yellow, milia-like papules and telangiectatic vessels developed. The papules were present particularly on the cheeks and forehead, gradually becoming very conspicuous and dominating the clinical picture. Trichoepitheliomas were found in 1 case. In adults, the eyelashes and eyebrows were either missing or irregularly distributed with defective and maldirected growth. Basal cell carcinomas were a frequent complication. The skin atrophy was referred to as vermiculate atrophoderma. Basal cell carcinomas may develop around the age of 35. Histological observations during the early stage include irregularly distributed and atrophic hair follicles, milia, dilated dermal vessels, lack of elastin or elastin in clumps. After light irradiation a tendency to increased repair activity was observed both in epidermis and in the dermal fibroblasts.

Histologic sections showed the dermis to be almost devoid of elastin in most areas with clumping of elastic material in other areas. The disorder had been transmitted through at least 4 generations with instances of male-to-male transmission.

The course of ACA is long-standing, from a few to several years, and it leads to extensive atrophy of the skin and, in some patients, to the limitation of upper and lower limb joint mobility.The outlook is good if the acute inflammatory stage of ACA is treated adequately. The therapeutic outcome is difficult to assess in patients with the chronic atrophic phase, in which many changes are only partially reversible.

Physicians should use serologic and histologic examination to confirm the diagnosis of ACA. Treatment consists of antibiotics including doxycycline and penicillin for up to four weeks in the acute case.

Poikiloderma vasculare atrophicans (PVA), sometimes referred to as parapsoriasis variegata or parapsoriasis lichenoides is a cutaneous condition (skin disease) characterized by hypo- or hyperpigmentation (diminished or heightened skin pigmentation, respectively), telangiectasia and skin . Other names for the condition include prereticulotic poikiloderma and atrophic parapsoriasis. The condition was first described by pioneer American pediatrician Abraham Jacobi in 1906. PVA causes areas of affected skin to appear speckled red and inflamed, yellowish and/or brown, gray or grayish-black, with scaling and a thinness that may be described as "cigarette paper". On the surface of the skin, these areas may range in size from small patches, to plaques (larger, raised areas), to neoplasms (spreading, tumor-like growths on the skin).

Mycosis fungoides, a type of skin lymphoma, may be a cause of PVA. The condition may also be caused by, associated with or accompany any of the following conditions or disorders: other skin lymphomas, dermatomyositis, lupus erythematosus, Rothmund-Thompson syndrome, Kindler syndrome, dyskeratosis congenita, and chronic radiodermatitis. Rare causes include arsenic ingestion, and the condition can also be idiopathic.

PVA may be considered a rare variant of cutaneous T-cell lymphoma, a non-Hodgkin's form of lymphoma affecting the skin. It may also be included among a number of similar conditions that are considered as precursors to mycosis fungoides. PVA is believed to be a syndrome closely associated with large-plaque parapsoriasis and its cohort retiform parapsoriasis; including PVA, all three conditions fit within an updated view of the once ambiguous classification scheme known as parapsoriasis.

Diabetic dermopathy (also known as "shin spots") is a type of skin lesion usually seen in people with diabetes mellitus. It is characterized by dull-red papules that progress to well-circumscribed, small, round, atrophic hyperpigmented skin lesions usually on the shins. It is the most common of several diabetic skin conditions, being found in up to 30% of diabetics. Similar lesions can occasionally be found in non-diabetics usually following trauma or injury to the area; however, >4 lesions strongly suggests diabetes.