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Benign Melanocytic Lesions
Published in Ashfaq A Marghoob, Ralph Braun, Natalia Jaimes, Atlas of Dermoscopy, 2023
Konstantinos Liopyris, Cristian Navarrete-Dechent, Silvia E. Mancebo, Michael A. Marchetti
Melanocytic nevi are common skin lesions and the primary differential diagnosis of early presentations of cutaneous melanoma. Their accurate recognition is critical for efficient skin cancer detection. Fortunately, the majority of melanocytic nevi can be correctly identified after careful clinical and dermatoscopic inspection as well as integration of patient- and lesion-related factors such as age, anatomic location, skin color, and clinical history. In this chapter, we review the common dermatoscopic patterns of melanocytic nevi, including reticular, globular, homogeneous, starburst, peripheral globules, multicomponent patterns, and their variants. We also discuss banal/common nevi, atypical/dysplastic nevi, growing nevi, and congenital nevi. Finally, we point out dermatoscopic features relevant to less common nevus subtypes, including halo nevi, balloon cell nevi, traumatized nevi, combined nevi, and nevi subjected to ultraviolet irradiation.
Disorders of Keratinization and Other Genodermatoses
Published in Ayşe Serap Karadağ, Lawrence Charles Parish, Jordan V. Wang, Roxburgh's Common Skin Diseases, 2022
Roselyn Stanger, Nanette Silverberg
Laboratory studies: Although a skin biopsy can confirm the diagnosis of an epidermal nevus, it is not the most important aspect of the diagnosis, as the underlying systemic manifestations are the causes of morbidity and mortality for these patients. Bloodwork should be guided by a multi-disciplinary approach. Other studies may include an MRI and CT scan. Genetic testing should be performed to clarify which epidermal nevus syndrome is affecting a particular patient; however, not all the gene mutations are known.
An introduction to skin and skin disease
Published in Rashmi Sarkar, Anupam Das, Sumit Sethi, Concise Dermatology, 2021
Black pigment (melanin), a polymer synthesized by melanocytes, protects against solar ultraviolet radiation (UVR). Melanocytes, unlike keratinocytes, do not have desmosomes but have long, branching dendritic projections that transport the melanin they synthesize to the surrounding cells. They originate from the embryonic neural crest. Melanocytes account for 5–10% of cells in the basal layer of the epidermis. Melanin is a polymer that is synthesized from the amino acid tyrosine with the help of a copper-containing enzyme, tyrosinase. Other pigments contribute rarely (e.g. bilirubin in jaundice or pigments derived from drugs such as minocycline or chlorpromazine). Exposure to the sun accelerates melanin synthesis, which explains suntanning. Skin color is mainly due to melanin and blood. The number of melanocytes per unit of body surface area is variable, depending on the site of the body but the density of melanocytes is the same in all humans, irrespective of race. The racial differences in complexion are attributed to the distribution and size of melanosomes, which disperse melanin to the keratinocytes. Melanocytes are completely destroyed in vitiligo. In albinism, melanin synthesis is defective. Localized increase in the synthesis of melanin leads to the development of freckles. Melanocytes in benign proliferation are referred to as nevi, and the malignant ones are known as melanomas.
The Markers Auxiliary in Differential Diagnosis of Early Melanomas and Benign Nevi Sharing Some Similar Features Potentially Leading to Misdiagnosis – A Review of Immunohistochemical Studies
Published in Cancer Investigation, 2022
Łukasz Kuźbicki, Anna A. Brożyna
Study results of marker can be binary when a given molecule is or is not detectable. However, most often the results of the percentage fraction of stained cells or the intensity of immunohistochemical staining constitute numbers on a continuous scale. In diagnostic tests continuous results are often dichotomized. Ultimately, what matters is whether the skin lesion is a nevus or a melanoma. However, this entails the need to introduce optimal thresholds of the marker level. A good practice allowing for objective analysis and comparison of research results would be their presentation using the receiver operating characteristic (ROC) curve illustrating the variability of the sensitivity and specificity of the diagnostic test for consecutive threshold values of the marker level. The measure of test quality constitutes the area under the ROC curve (AUC) which allows quantifying the overall ability to discriminate between two outcomes: benign or malignant lesion (55–60). The test is considered perfect if AUC = 1.0, excellent if 1.0 > AUC ≥0.9, good if 0.9 > AUC ≥0.8, fair if 0.8 > AUC ≥0.7, poor if 0.7 > AUC >0.5 and non-useful if AUC ≤0.5 (57).
Blue nevi of the palpebral conjunctiva: report of 2 cases and review of literature
Published in Orbit, 2022
Armida L. Suller, Jiawei Zhao, Nickisa M. Hodgson, Gulsun Erdag, Raja R. Seethala, Aparna Ramasubramanian, Roxana Fu
Clinically, blue nevi can simulate other pigmented lesions of the conjunctiva, such as common nevus, racial melanosis, PAM, melanoma, and pigmented squamous cell carcinoma. Common nevus is a benign melanocytic tumor, which typically presents as a variably pigmented, circumscribed, slightly elevated lesion with intralesional cysts in the bulbar conjunctiva.25 Although common nevus is the most frequently encountered pigmented tumor on the ocular surface, it rarely presents in the tarsal conjunctiva.25 Racial melanosis is a bilateral condition typically found in darkly pigmented individuals and appears as flat conjunctival pigmentation.31 PAM presents as a diffuse, flat, patchy brown pigmentation of the bulbar conjunctiva, but it can involve the palpebral conjunctiva as well.31 Malignant melanoma appears as a brown to tan, elevated mass in the bulbar conjunctiva with surrounding PAM and prominent feeder vessels.30,31 Involvement of the palpebral conjunctiva or eyelid margin is unusual in melanoma, but it is associated with higher risk of recurrence, orbital exenteration, metastasis, and death.30 Given the rarity of benign lesions, such as blue nevi in the palpebral conjunctiva, any pigmented lesion in this location should raise suspicion of melanoma.30 Squamous cell carcinoma can be pigmented in rare cases and has been documented in the bulbar and palpebral conjunctiva in both Whites and non-Whites.32,33
Systematic review of machine learning for diagnosis and prognosis in dermatology
Published in Journal of Dermatological Treatment, 2020
Kenneth Thomsen, Lars Iversen, Therese Louise Titlestad, Ole Winther
Three systems had multiway output functions (12,22,28). The rest had binary outcomes. Five publications used more than 1000 images (12,20,29–31); seven publications used between 500 and 992 images (21,23,27,28,32–34); the rest used between 100 and 370 images (Table 1). The ratio of training to test set varied considerably. Data saved for the test set varied from 0% (35) to 68% (36) of the entire data set. Seven publications did not describe the ratio. Twenty of the 23 publications used the binary outcome MM or benign lesions (binary classification). The benign lesions were most often nevi. Some studies also included seborrheic keratosis, actinic keratosis, lentigines, basal cell carcinoma (BCC) and dermatofibromas. Eight publications did not describe the benign lesions; data not shown.