Amelanotic melanoma in oculocutaneous albinism: a genetic, dermoscopic and reflectance confocal microscopy study

Characterizing melanoma in the setting of oculocutaneous albinism: an analysis of the literature

Although it is established that individuals with albinism have increased risks for nonmelanoma skin cancers, melanomas occurring in the setting of albinism are rare. PubMed and Google Scholar were searched for individual case reports describing melanoma in individuals with oculocutaneous albinism (OCA). All published cases characterizing individuals with albinism and melanoma in the medical literature were gathered to evaluate any epidemiologic or histologic differences from melanomas arising in the general population. Frequencies of melanoma characteristics between the OCA literature cohort and general population were compared using Clopper-Pearson confidence intervals. From 1952 to 2018, at least 64 cases of melanoma in 56 individuals with albinism were reported in the global medical literature. The median age of diagnosis for melanoma in individuals with albinism was 41 years, and the median Breslow depth at diagnosis was 2.0 mm. The subtypes of melanoma were nodular in 33% and superficial spreading in 46% of these cases, respectively. Amelanotic melanomas comprised 65% of the cases in our OCA cohort; however, histologic subtypes were only available for fourteen of the amelanotic cases. Finally, 17% of melanomas in patients with albinism arose from preexisting lesions. Despite their rarity, melanomas arising in oculocutaneous albinism have distinct characteristics from melanomas arising in the general population. Clinicians should consider a differential diagnosis of melanoma for any potential skin malignancies in individuals with albinism.

Phenotypic and Dermoscopic Patterns of Familial Melanocytic Lesions: A Pilot Study in a Third-Level Center

Cutaneous melanoma is a highly aggressive skin cancer. It is estimated that 5% to 10% of the underlying mutations are hereditary and responsible for familial (or hereditary) melanoma. These patients are prone to the early development and higher risk of multiple melanomas. In recent years, an increasing number of genes have been identified thanks to genetic testing, allowing the subsequent surveillance of individuals at risk, yet it is still difficult to predict the presence of these mutations on a clinical basis. In this scenario, specific phenotypic and dermoscopic features could help clinicians in their identification. The aim of this work has been to correlate mutations to prevalent dermoscopic patterns, paving the way for reference models useful in clinical practice. In our cohort, out of 115 patients referred to genetic counseling for melanoma, 25 tested positive (21.7%) for critical mutations: CDKN2A (n = 12), MITF (n = 3), BAP1 (n = 1), MC1R (n = 3), PTEN (n = 1), TYR (n = 2), OCA2 (n = 1), and SLC45A2 (n = 2). The phenotype profiles obtained through the digital acquisition, analysis, and description of both benign and malignant pigmented lesions showed a predominance of the type II skin phenotype, with an elevated mean total nevus number (182 moles, range 75-390). As for dermoscopic features, specific mutation-related patterns were described in terms of pigmentation, areas of regression, and vascular structures. Although further studies with larger cohorts are needed, our work represents the beginning of a new approach to the study and diagnosis of familial melanoma, underlining the importance of clinical and dermoscopic patterns, which may constitute a reference model for each gene, enabling comparison.

Prevalence of premalignant and malignant skin lesions in oculocutaneous albinism patients

OBJECTIVE

Oculocutaneous albinism describes a group of pigmentary disorders that lead to skin sensitivity and predisposition to skin malignances.

AIMS

To analyze clinical and epidemiological data in oculocutaneous albinism patients and to determine the prevalence of malignant skin lesions, assessing possible risk factors for skin cancer.

METHODS

Cross-sectional study evaluating epidemiological data, habits of sun exposure and sun protection, and clinical examination of albino patients followed in a reference dermatology outpatient clinic in Brasil. Our primary outcome was the occurrence of malignant skin lesions in biopsied tissues.

RESULTS

Of 74 patients analyzed, 11 (15%) had one or more suspicious lesions and were biopsied, of which 8 (72.7%) patients presented with basal cell carcinomas, 7 (63.3%) presented with squamous cell carcinoma, and 1 (9%) presented with melanoma. Moreover, 32(43%) patients presented with actinic keratosis. Age, female gender, previous history of sunburn, history of malignant lesions and history of sun exposure without photoprotection were associated with the presence of malignant lesions.

LIMITATIONS

Unicentric, non-aleatory sample.

CONCLUSIONS

There was a high prevalence of malignant and pre-malignant lesions in this population. Some potentially modifiable risk factors were associated with the occurrence of malignant skin lesions.

Clinical and Dermoscopic Features Associated With Difficult-to-Recognize Variants of Cutaneous Melanoma: A Systematic Review

Importance

The clinical and dermoscopic features of the vast majority of uncommon variants of cutaneous melanoma have been rarely reported, leading to difficulty in making accurate diagnoses.

Objective

To define the main clinical and dermoscopic features of the most frequently reported but uncommon histologic variants of cutaneous melanoma.

Evidence Review

A 2-step systematic review of the literature was performed (from inception to November 2018) using PubMed, Embase, and Cochrane Central Register of Controlled Trials databases. The first step identified those uncommon variants of melanoma for which at least 1 case reporting dermoscopy was described in the literature. The keywords searched were melanoma, uncommon, rare, dermoscopy, and dermatoscopy. In the second step, each previously identified uncommon variant was searched for in the same databases by combining the following terms with melanoma, dermoscopy, and dermatoscopy: amelanotic, hypopigmented, animal, melanocytoma, balloon, desmoplastic, follicular, nested, nevoid, dermal, spitz*, spindle, and verrucous. The institution's database was also searched from January 2012 to September 2019 for histopathologically confirmed cases of the same melanoma variants. Each reviewer also assessed the quality of reporting in the included articles based on previously described guidelines.

Findings

In total, 62 articles met the inclusion criteria, reporting 433 melanoma cases. An additional 56 cases of uncommon melanoma variants were retrieved from the institution's database for a total of 489 cases: 283 cases of amelanotic superficial spreading melanoma, 18 cases of animal-type and pigmented epithelioid melanocytoma, 7 cases of balloon cell melanoma, 71 cases of desmoplastic melanoma, 3 cases of follicular melanoma, 10 cases of nested melanoma, 33 cases of nevoid melanoma, 2 cases of primary dermal melanoma, 57 cases of spitzoid melanoma, and 5 cases of verrucous melanoma. These variants of melanoma occurred more frequently in women than men (147 cases vs 132 cases). Clinically, these tumors were mainly palpable (162 of 217 [74.7%]) or amelanotic (283 of 489 [57.9%]) lesions that could resemble other benign or malignant skin conditions; dermoscopy typically revealed a homogeneous pinkish background, white structures, and polymorphic vessels. The mean age of all included was 58 years (range, 1-89 years).

Conclusions and Relevance

Uncommon melanoma variants may resemble both inflammatory disorders and other cutaneous neoplasms, representing a diagnostic pitfall even for the most experienced dermatologist. The purpose of this systematic review was to provide an extensive and detailed overview of specific clinical and dermoscopic features of each uncommon melanoma variant, highlighting the main criteria for differentiating these variants from other benign or malignant skin lesions.

Germline and somatic albinism variants in amelanotic/hypomelanotic melanoma: Increased carriage of TYR and OCA2 variants

Amelanotic/hypomelanotic melanoma is a clinicopathologic subtype with absent or minimal melanin. This study assessed previously reported coding variants in albinism genes (TYR, OCA2, TYRP1, SLC45A2, SLC24A5, LRMDA) and common intronic, regulatory variants of OCA2 in individuals with amelanotic/hypomelanotic melanoma, pigmented melanoma cases and controls. Exome sequencing was available for 28 individuals with amelanotic/hypomelanotic melanoma and 303 individuals with pigmented melanoma, which were compared to whole exome data from 1144 Australian controls. Microarray genotyping was available for a further 17 amelanotic/hypomelanotic melanoma, 86 pigmented melanoma, 147 melanoma cases (pigmentation unknown) and 652 unaffected controls. Rare deleterious variants in TYR/OCA1 were more common in amelanotic/hypomelanotic melanoma cases than pigmented melanoma cases (set mixed model association tests P = 0.0088). The OCA2 hypomorphic allele p.V443I was more common in melanoma cases (1.8%) than controls (1.0%, X2 P = 0.02), and more so in amelanotic/hypomelanotic melanoma (4.4%, X2 P = 0.007). No amelanotic/hypomelanotic melanoma cases carried an eye and skin darkening haplotype of OCA2 (including rs7174027), present in 7.1% of pigmented melanoma cases (P = 0.0005) and 9.4% controls. Variants in TYR and OCA2 may play a role in amelanotic/hypomelanotic melanoma susceptibility. We suggest that somatic loss of function at these loci could contribute to the loss of tumor pigmentation, consistent with this we found a higher rate of somatic mutation in TYR/OCA2 in amelanotic/hypomelanotic melanoma vs pigmented melanoma samples (28.6% vs 3.0%; P = 0.021) from The Cancer Genome Atlas Skin Cutaneous Melanoma collection.

[Oculocutaneous and ocular albinism]

Albinism can be divided into oculocutaneous albinism (OCA) and ocular albinism (OA). In the differential diagnostics these can be distinguished from rarer syndromes with partial albinism, which are frequently associated with susceptibility to infections and neurological symptoms. The OCA is an autosomal recessive inherited disease of melanin biosynthesis, which leads to complete or partial loss of melanin in the skin, hair follicles and eyes. Of the seven currently known subtypes (OCA 1-7), four are well-characterized (OCA 1-4). These are based on gene mutations, which code for tyrosinase, a key enzyme in melanin synthesis and for further proteins. These play an important role in the catalytic activity of tyrosinase and the structure and function of melanosomes. In the presence of these subtypes, the clinical symptoms and the course of the disease show a pronounced variability, especially in the type and extent of pigmentation of the skin and hair as well as the severity of eye involvement, which makes the phenotypic classification difficult. Treatment priorities are a consistent protection from UV light for prophylaxis against skin cancer and regular preventive investigations. The ocular alterations typical for albinism necessitate timely diagnostics and care by institutions specialized in ophthalmology. Novel strategies for systemic treatment of subtypes of albinism are in preclinical testing. The OA without skin involvement shows X‑linked inheritance, is much rarer and is characterized by reduced pigmentation of the retina and iris, nystagmus and macular hypoplasia, sometimes with substantial loss of visual acuity. The typical ocular symptoms of OA can be manifested to a varying extent in all forms of OCA.