Solar lentigo

Solar lentigo, also known as senile lentigo, refers to a clearly demarcated pigmented skin disease caused by natural or artificial ultraviolet radiation. This disease is prone to occur in sun-exposed areas such as the face, forearms, and back of the hands, and is characterized by dark brown patches with clear boundaries. Very few patients will undergo malignant transformation.

1, Etiology and Pathogenesis

This disease is related to senile skin degeneration and skin photoaging.

2. Clinical manifestations

This disease is more common in elderly people over 60 years old, and more common in women than in men. The incidence rate increases with age. The skin lesions are dark brown or brown macules with relatively clear boundaries, which are round, oval or irregular in shape, mostly less than 5mm in diameter, and can also be scattered up to the size of a walnut, and sometimes can merge into pieces. It can be seen in any part of the body, and is more common in the face and forearms that are often exposed to ultraviolet radiation, especially the back of the hands. As the skin lesions age, the patches will increase, expand, and the color will deepen. There are no subjective symptoms. Very few patients will undergo malignant transformation, which is called malignant lentigo.

3. Pathological characteristics

Pathologically, the disease is manifested by an increase in melanocytes in the basal cell layer, an enhanced dopa reaction, thinning of the epidermis, and obvious elongation of the epidermal protuberances, which are club-shaped and often branch and fuse with each other. A small amount of mononuclear cell infiltration mixed with melanophages can be seen around the blood vessels in the dermis, and there is no tendency to malignant transformation. Histopathological manifestations are hyperkeratosis and incomplete keratinization. Generally, there is no granular layer, the basal cells are poorly developed, the arrangement is disordered, and some cells are atypical. Some epidermal changes have the characteristics of senile lentigo, with elongated epidermal protuberances and increased epidermal pigmentation. A certain degree of collagen degeneration and elastic fiber degeneration can be seen in the dermis, and lymphocytes and plasma cells often infiltrate around small blood vessels.

4. Diagnosis and differential diagnosis

Based on the medical history and clinical characteristics, this disease is generally not difficult to diagnose. However, pathological examination is required for confirmation.
(i) Simple freckle nevus
Simple freckle nevus is more common in children. Histopathology shows an increase in the number of melanocytes in the basal layer of the epidermis, and the epidermal processes are long to moderately elongated. (ii) Junctional nevus
Histopathology of junctional nevus shows that the nevus cells are arranged in nests and lack dendritic processes.
(iii) Malignant lentigo nevus
The epidermis of malignant lentigo nevus is atrophic, and the basal layer has atypical melanocytes that are non-nested.
(iv) Actinic keratosis
The surface of the skin lesions of actinic keratosis is rough and has keratotic scales. Histopathology shows that the epidermis is hyperkeratotic or parakeratotic, with alternating acanthosis and atrophy.
(v) Pigmented seborrheic keratosis
The base of pigmented seborrheic keratosis does not grow downward, and the boundaries on both sides are clear. Squamous cells and basaloid cells can be seen in the hyperplastic epidermis.

5. Treatment

This disease may be a precancerous lesion. If there is clinical suspicion, surgical excision and pathological confirmation are required. However, in recent years, photodynamic therapy has achieved good clinical results in the treatment of precancerous changes in the skin. For those cases that refuse or are not suitable for surgical treatment, it is undoubtedly a major clinical breakthrough. Most patients' skin lesions (excluding precancerous lesions) can be removed by laser.
(I) CO2 laser For those with a small number of lesions, a small area of ​​a single lesion, and lesions that are slightly protruding from the skin surface, CO2 laser can be used for removal. In the past, when traditional CO2 laser was used to treat solar lentigo, continuous waves were prone to produce scars. Now, ultra-pulsed CO2 laser is often used to avoid scar formation or reduce the degree of scarring to the greatest extent. The treatment operation is the same as the ultra-pulsed CO2 laser treatment part of seborrheic keratosis.
(II) Q-switched laser
Q-switched lasers include Q-switched Nd:YAG laser, Q-switched ruby ​​laser, Q-switched alexandrite laser, etc. Although the above treatments are effective, they are all invasive and can easily cause adverse reactions such as post-inflammatory pigmentation and depigmentation. The recovery time is long, which affects the patient's daily life and work.
(III) Intense pulsed light
Intense pulsed light (IPL) is a relatively safe, effective and convenient method for treating solar lentigo. Reasonable parameter settings generally do not cause side effects such as post-inflammatory pigmentation. Clinical treatment can refer to freckle treatment.

Source: Solar lentigo