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Nail melanoma (NM) is an important differential diagnosis in patients with longitudinal melanonychia. However, diagnosis is often challenging as it is difficult to differentiate from other pigmented nail disorders. The main challenge for diagnosis is obtaining adequate nail matrix biopsy specimens for histopathological assessment. Furthermore, the histopathological changes in the early stages of NM are subtle and contribute to a delay in diagnosis and care. Therefore, the integration of clinical and histopathological analyses is essential. Clinical and dermoscopic features, such as a broadened width of asymmetric bands in an irregular pattern, with multicolour pigmentation, periungual pigmentation, and continuous growth, are features that support the diagnosis of NM. The essential histological features that must be assessed are cellular morphology, architectural features, melanocyte density, and inflammatory changes. The reported mutations in NMs were BRAF (0-43%), NRAS (0-31%), KIT (0-50%), NF1 (0-50%), and GNAQ (0-25%). Surgery is the primary treatment for NM. The recommended treatment for in situ or minimally invasive NM is functional surgery, but cases with suspected bone invasion should be treated with amputation. Targeted therapy and immunotherapy are indicated for advanced stages of NM. This review summarizes the updated guidelines for the diagnosis and treatment of NM., (© 2022 European Academy of Dermatology and Venereology.)

Background: The current histopathological classifications for actinic keratosis (AK) are subjective, and histopathological factors predicting the progression into invasive squamous cell carcinoma (SCC) remain unclear., Objectives: To quantitatively assess the histopathological findings of AK and to investigate the predisposing factors for malignant transformation of AK., Methods: A total of 502 AK specimens were retrospectively reviewed. The AK lesions were divided into the atrophic, intermediate, hypertrophic and bowenoid types. Histopathological features were quantitatively analysed using computer-aided image analysis., Results: The epidermal thickness excluding the horny layer increased with statistical significance (P < 0.001) in order of atrophic, intermediate, hypertrophic and bowenoid type. The proportion of keratinocytic atypia was not significantly different among subtypes, except for the bowenoid type. Five of 498 cases were confirmed to develop into SCC. Bowenoid type, epidermal thickening and higher proportion of keratinocytic atypia were significantly associated with progression to invasive SCC in univariate analysis (OR = 12.571, 95% CI: 1.392-113.57; OR = 1.004, 95% CI: 1.001-1.007; OR = 1.069, 95% CI: 1.011-1.130, respectively). In multivariate analysis, only the proportion of keratinocytic atypia was an independent predisposing factor for progression to invasive SCC (OR = 1.069; 95% CI: 1.011-1.130)., Conclusions: Histopathological subtypes based on the essential change of the epidermis well correlated with the actual epidermal thickness excluding the horny layer. The overall severity of keratinocytic atypia might be an independent risk factor for malignant transformation of AK., (© 2020 European Academy of Dermatology and Venereology.)

Introduction: Non-melanoma skin cancers (NMSCs) are the most common cancers in the world, but the risk of internal malignancy in patients with NMSC has not been well investigated., Objectives: We aimed to assess the risk of internal malignancy in patients with NMSC compared with controls without NMSC in Korean population., Methods: This nationwide cohort study, compared 27 259 NMSC patients with 54 518 matched controls without NMSC, 40 years or older using the data from Korea Health Insurance Review and Assessment Service from 2007 to 2016. The first 2 years were washout period, and we followed the patients for 8 years to observe the development of any internal malignancies after a diagnosis of NMSC. The Cox proportional hazard model was used to determine the hazard ratios (HRs) for developing internal malignancies., Results: The overall risk of internal malignancies at all sites was 2727.7 and 1392.4 per 100 000 person-years for the patients with NMSC and controls, respectively. The risk was significantly higher in the patients with NMSC (HR 1.866, 95% confidence interval [CI] 1.768-1.970). Bone cancer showed the highest risk (HR 12.745, 95% CI 6.288-25.834), followed by nasal cavity and larynx (HR 10.279, 95% CI 6.178-7.103), oral cavity and pharynx (HR 10.211, 95% CI 7.375-14.137), anus and anal canal (HR 8.147, 95% CI 3.893-17.051) and cervical (HR 5.900, 95% CI 3.694-9.423) cancers with risks greater than fivefold higher in NMSC patients compared with the controls. The risks of cancers of the thorax, oesophagus, breast, lung, stomach, thyroid gland and non-Hodgkin's lymphoma were also statistically higher in the patients with NMSC. In contrast, the risks of cancers of the colon and rectum were found to be significantly decreased in the patients with NMSC (HR 0.765, 95% CI 0.657-0.890)., Conclusion: Patients with NMSC require careful screening and follow-up for internal malignancy., (© 2019 European Academy of Dermatology and Venereology.)

β-catenin plays an important role in hair morphogenesis. Previously, the nuclear and cytoplasmic localizations of β-catenin were identified in hair-matrix cells. To evaluate β-catenin expression in the nail matrix, we obtained human nail units. Immunohistochemistry for β-catenin was used to evaluate sections of normal nail units and of sections from a single case of onychomatricoma. In the nail unit, β-catenin was expressed in the nucleus and cytoplasm of the suprabasal nail-matrix cells. Of the other epithelial-cell types, only the cell membrane was β-catenin-positive. In the nail tissue from the onychomatricoma case, β-catenin was expressed in the nucleus and cytoplasm of the upper epithelial layers. Our result suggests that β-catenin plays an important role in nail formation. In addition, β-catenin expression in onychomatricoma supports the presence of nail-matrix cells in this condition. To our knowledge, this is the first report of β-catenin expression in the nucleus and cytoplasm of the nail matrix., (© 2013 British Association of Dermatologists.)

Background: Giant congenital melanocytic naevi (GCMN) are known risk factors for the development of melanoma. However, melanoma risk among Asians is rarely evaluated., Objectives: To evaluate the clinical characteristics and risk of melanoma development from GCMN in Koreans, we performed a nationwide retrospective cohort study in Korea. GCMN were defined as those comprising ≥5% body surface area in children or measuring ≥20cm in adults., Methods: In total, 131 patients with GCMN were enrolled, with a mean age of 10·3years (range: birth-70years)., Results: The posterior trunk was the most common site (67, 51·1%), followed by lateral trunk, anterior trunk, legs, both anterior and posterior trunk, buttocks, and arms. Satellite naevi were present in 69 cases (52·7%), and axial areas were more commonly involved in patients with satellite naevi than in those without satellite lesions. Atypical features such as rete ridge elongation and bridges were seen, and, among these, pagetoid spread and ballooning cell changes were more common in patients <4years old. Proliferative nodules were found in three cases. Melanomas had developed in three of 131 patients (2·3%; a 6-year-old girl, a 14-year-old girl and a 70-year-old man), and the incidence rate was 990 per 100000 person-years. Melanomas in these three patients consisted of two cutaneous melanomas and one extracutaneous meningeal melanoma., Conclusions: We should be aware of melanoma development from GCMN, and lifelong follow-up is required due to the risk of melanoma arising in GCMN., (© 2011 The Authors. BJD © 2011 British Association of Dermatologists.)

Background: Extranodal natural killer T (NK/T) cell lymphoma is subcategorized into 'nasal' and 'nasal-type' NK/T-cell lymphomas according to the primary sites of anatomical involvement., Objectives: The aim of this study was to characterize the cutaneous manifestations of the skin involving extranodal NK/T-cell lymphoma and to define the distinctive features of 'nasal' and 'nasal-type'. In addition, the prognostic factors that affect overall survival were investigated., Methods: A retrospective case study of 18 patients with extranodal NK/T-cell lymphoma with cutaneous involvement was performed., Results: The NK/T-cell lymphomas usually occurred in middle-aged, male patients. Most of the patients presented with either cellulitis or ulcer. A facial predilection for the location of the lesion was noted. The characteristic features of the 'nasal-type' compared with the 'nasal' were a localized involvement of the skin, less aggressive clinical course and better survival outcome., Conclusions: Extranodal NK/T-cell lymphomas are extremely aggressive regardless of their subgroup. However, the 'nasal-type' NK/T-cell lymphoma was clinically less aggressive, more localized and had a better outcome compared with the other type. Cellulitis and ulcer were the major cutaneous manifestations.

Background: Naevus of Ota manifests various colours ranging from light brown to blue. Naevus colours have been claimed to reflect the depth of melanin pigments but the claim has rarely been substantiated by quantitative studies., Objectives: We attempted both quantitative and qualitative analyses of the naevus of Ota to find out relations between histological patterns or parameters of melanin/melanocytes and lesion colours., Methods: Lesion colours were determined by one of the authors and were confirmed by a separate panel of dermatologists. Forty biopsy specimens of naevus of Ota were evaluated by both computer-assisted quantitative image analysis and a previously proposed conventional pattern analysis., Results: The mean area fraction (AFmean) of melanin, the depth of the maximum area fraction of melanin (level of AFmax) and the depth of the deepest infiltrating melanocyte were significantly greater or deeper for bluish lesions than brownish lesions. Based on the qualitative pattern analysis we found that all the brownish lesions demonstrated superficial dermal melanin pigments, whereas bluish lesions tended to show more heterogeneous histological patterns. Eyelid lesions, all of which were bluish, revealed greater AF(mean) value than cheek lesions, presenting as either brownish or bluish colours., Conclusions: Quantitative analysis indicated that pigment density measures such as AFmean could be as important as the depth of melanocytes in the explanation of the lesion colours in naevus of Ota. However, qualitative pattern analysis failed to link specific patterns with lesion colours, especially in bluish lesions, probably due to the lack of consideration of the pigment density.

Bowenoid papulosis (BP) of the genitalia, characterized by the histological findings of a squamous cell carcinoma, follows a largely benign clinical course. The detection of oncogenic human papilloma viruses (HPV) from BP points to an aetiological role of these viral infections. A 47-year-old man with multiple genital skin lesions was seen over a 10-year period with the diagnosis of BP. Recently, he attended again with a recurrent genital tumour that was diagnosed as squamous cell carcinoma. His genital lesions progressed and became polymorphic in appearance, from a wart-like tumour to a reddish invasive plaque. To screen for the presence of different HPV sequences from different skin lesions and to correlate each HPV type with distinct clinical manifestations, polymerase chain reaction and single-strand conformational polymorphism (PCR-SSCP) were performed. PCR-SSCP revealed the presence of several types of HPV from different genital lesions. Sequencing results disclosed that he had a mixed infection of HPV6b, HPV16, HPV18 and HPV33, respectively. Interestingly, the clinical findings were fairly well correlated with the oncogenic potential of HPV found from each lesion.

A mottled black pigmented patch on the sole of the foot is reported. Clinically, the lesion closely mimicked acral lentiginous melanoma in situ. However, the histologic findings revealed melanocytic hyperplasia with minimal cytologic atypia confined to the epidermis. Irregular pigmented patches in the acral region comprise a heterogenous group of lesions that range from benign melanocytic hyperplasia to acral lentiginous melanoma.