Subungual Melanocytic Lesions in Pediatric Patients. / Lesiones melanocíticas subungueales en la edad pediátrica.

The study of subungual melanocytic lesions can present challenges because of the clinical and histologic characteristics of the nail unit and the difficulty of performing nail biopsies and processing specimens. These lesions can be even more challenging in children due to differences in clinical and epidemiological profiles between the adult and pediatric populations. Many of the clinical features of subungual melanocytic lesions that would raise alarm in an adult do not have the same implications in children. Consensus is also lacking on when a nail biopsy is needed to rule out malignancy in the pediatric setting. In view of these considerations and the rarity of subungual melanoma in childhood, the recommended approach in most cases is a watch-and-wait strategy. Subungual melanocytic lesions in children may also show atypical histopathologic features that are not necessarily associated with aggressive behavior. Subungual melanoma is very rare in childhood, with just 21 cases described to date. None of the patients developed visceral metastasis or died as a result and the diagnosis was controversial in many of the cases. Considering the above and the significantly higher frequency and particular characteristics of longitudinal melanonychia with a benign etiology in children, subungual melanocytic lesions should be managed differently in this setting than in adults. In most cases, a watch-and-wait approach is the most appropriate strategy.

Position paper on a simplified histopathological classification of basal cell carcinoma: results of the European Consensus Project.

BACKGROUND: Histopathological classification of basal cell carcinoma (BCC) has important prognostic and therapeutic implications, but reproducibility of BCC subtyping among dermatopathologists is poor. OBJECTIVES: To obtain a consensus paper on BCC classification and subtype definitions. METHODS: A panel of 12 recognized dermatopathologists (G12) from nine European countries used a modified Delphi method and evaluated 100 BCC cases uploaded to a website. The strategy involved five steps: (I) agreement on definitions for WHO 2018 BCC subtypes; (II) classification of 100 BCCs using the agreed definitions; (III) discussion on the weak points of the WHO classification and proposal of a new classification with clinical insights; (IV) re-evaluation of the 100 BCCs using the new classification; and (V) external independent evaluation by 10 experienced dermatopathologists (G10). RESULTS: A simplified classification unifying infiltrating, sclerosing, and micronodular BCCs into a single "infiltrative BCC" subtype improved reproducibility and was practical from a clinical standpoint. Fleiss' κ values increased for all subtypes, and the level of agreement improved from fair to moderate for the nodular and the unified infiltrative BCC groups, respectively. The agreement for basosquamous cell carcinoma remained fair, but κ values increased from 0.276 to 0.342. The results were similar for the G10 group. Delphi consensus was not achieved for the concept of trichoblastic carcinoma. In histopathological reports of BCC displaying multiple subtypes, only the most aggressive subtype should be mentioned, except superficial BCC involving margins. CONCLUSIONS: The three BCC subtypes with infiltrative growth pattern, characteristically associated with higher risk of deep involvement (infiltrating, sclerosing, and micronodular), should be unified in a single group. The concise and encompassing term "infiltrative BCCs" can be used for these tumors. A binary classification of BCC into low-risk and high-risk subtypes on histopathological grounds alone is questionable; correlation with clinical factors is necessary to determine BCC risk and therapeutic approach.

Subungual Melanocytic Lesions: Key Clinical and Pathologic Concepts and Biopsy Techniques.

Both dermatologists and pathologists sometimes find daunting the evaluation of melanonychia (especially subungual melanocytic lesions) because of the fear of performing nail surgery due to the risk of dystrophy, difficulties processing and interpreting nail biopsy specimens, and a general lack of experience in the field. Nevertheless, mastery of nail biopsy techniques, correct processing and orientation of specimens, and familiarity with the histologic particularities of the nail apparatus can attenuate the undoubted complexity and facilitate the tasks involved. Longitudinal excision is the biopsy technique that ensures the simplest histologic interpretation, and it is associated with a low risk of nail dystrophy when performed correctly. Clinical and epidemiological data are crucial. Subungual melanoma in childhood, for instance, is very rare and even lesions with atypical clinical and/or histologic features are probably benign. The presence of suprabasal melanocytes and other findings that would suggest malignancy at other sites are considered normal in the nail apparatus. Subungual melanoma shows a lentiginous pattern in the early stages of disease, and detection of an inflammatory infiltrate accompanying atypical lentiginous subungual lesions would appear to be one of the first diagnostic findings.

Subungual Melanocytic Lesions: Key Clinical and Pathologic Concepts and Biopsy Techniques. / Lesiones melanocíticas subungueales: claves clínico-patológicas y técnicas de biopsia.

Both dermatologists and pathologists sometimes find daunting the evaluation of melanonychia (especially subungual melanocytic lesions) because of the fear of performing nail surgery due to the risk of dystrophy, difficulties processing and interpreting nail biopsy specimens, and a general lack of experience in the field. Nevertheless, mastery of nail biopsy techniques, correct processing and orientation of specimens, and familiarity with the histologic particularities of the nail apparatus can attenuate the undoubted complexity and facilitate the tasks involved. Longitudinal excision is the biopsy technique that ensures the simplest histologic interpretation, and it is associated with a low risk of nail dystrophy when performed correctly. Clinical and epidemiological data are crucial. Subungual melanoma in childhood, for instance, is very rare and even lesions with atypical clinical and/or histologic features are probably benign. The presence of suprabasal melanocytes and other findings that would suggest malignancy at other sites are considered normal in the nail apparatus. Subungual melanoma shows a lentiginous pattern in the early stages of disease, and detection of an inflammatory infiltrate accompanying atypical lentiginous subungual lesions would appear to be one of the first diagnostic findings.

SARS-CoV-2 endothelial infection causes COVID-19 chilblains: histopathological, immunohistochemical and ultrastructural study of seven paediatric cases.

BACKGROUND: Chilblains ('COVID toes') are being seen with increasing frequency in children and young adults during the COVID-19 pandemic. Detailed histopathological descriptions of COVID-19 chilblains have not been reported, and causality of SARS-CoV-2 has not yet been established. OBJECTIVES: To describe the histopathological features of COVID-19 chilblains and to explore the presence of SARS-CoV-2 in the tissue. METHODS: We examined skin biopsies from seven paediatric patients presenting with chilblains during the COVID-19 pandemic. Immunohistochemistry for SARS-CoV-2 was performed in all cases and electron microscopy in one. RESULTS: Histopathology showed variable degrees of lymphocytic vasculitis ranging from endothelial swelling and endotheliitis to fibrinoid necrosis and thrombosis. Purpura, superficial and deep perivascular lymphocytic inflammation with perieccrine accentuation, oedema, and mild vacuolar interface damage were also seen. SARS-CoV-2 immunohistochemistry was positive in endothelial cells and epithelial cells of eccrine glands. Coronavirus particles were found in the cytoplasm of endothelial cells on electron microscopy. CONCLUSIONS: Although the clinical and histopathological features were similar to other forms of chilblains, the presence of viral particles in the endothelium and the histological evidence of vascular damage support a causal relation of the lesions with SARS-CoV-2. Endothelial damage induced by the virus could be the key mechanism in the pathogenesis of COVID-19 chilblains and perhaps also in a group of patients severely affected by COVID-19 presenting with features of microangiopathic damage. What is already known about this topic? Despite the high number of cases of chilblains seen during the COVID-19 pandemic, a definite causative role for SARS-CoV-2 has not yet been proven. Different pathogenetic hypotheses have been proposed, including coagulation anomalies, interferon release and external factors. What does this study add? The demonstration of SARS-CoV-2 in endothelial cells of skin biopsies by immunohistochemistry and electron microscopy confirms that these lesions are part of the spectrum of COVID-19. Virus-induced vascular damage and secondary ischaemia could explain the pathophysiology of COVID-19 chilblains. Our findings support the hypothesis that widespread endothelial infection by SARS-CoV-2 could have a pathogenetic role in the severe forms of COVID-19. Linked Comment: Wetter. Br J Dermatol 2020; 183:611.

Perianal nodule in a young woman.

A young woman presented with a perianal nodular lesion, which was found to have histopathological findings of hidradenoma papilliferum. The anal skin is an uncommon location for this neoplasm.

Dermatomyositis panniculitis: a clinicopathological and immunohistochemical study of 18 cases.

BACKGROUND: Panniculitis occurring in dermatomyositis is uncommon, with only a few cases described in the literature, most of them as case reports. OBJECTIVE: This report describes the clinicopathological and immunohistochemical findings in a series of 18 patients with panniculitis associated with dermatomyositis. METHODS: In each patient, we collected the clinical data of the cutaneous lesions as well as the characteristic clinical and laboratory findings. A series of histopathologic findings was recorded in the biopsy of each patient. A panel of antibodies was used in some cases to investigate the immunophenotype of the infiltrate. Data of treatment and follow-up were also collected. RESULTS: Of the 18 patients, 13 were female and 5 were male, ranging in age from 13 to 74 years (median, 46.4 years). In addition to panniculitis, all patients presented pathognomonic cutaneous findings of DM and reported proximal muscle weakness prior to the diagnosis of panniculitis. Muscle biopsy was performed in 17 patients and MRI in one, all with the diagnosis of inflammatory myopathy. None of the patients presented any associated neoplasia. Panniculitis lesions were located in the upper or lower limbs. Histopathology showed a mostly lobular panniculitis with lymphocytes as the main component of the infiltrate. Most cases showed also numerous plasma cells and lymphocytes surrounding necrotic adipocytes (rimming) were frequently seen. Lymphocytic vasculitis and abundant mucin interstitially deposited between collagen bundles of the dermis were also frequent findings. Late-stage lesions showed hyaline necrosis of the fat lobule and calcification. Immunohistochemistry demonstrated that most lymphocytes of the infiltrate were T-helper lymphocytes, with some B lymphocytes in the lymphoid aggregates and small clusters of CD-123-positive plasmacytoid dendritic cells in the involved fat lobule. CONCLUSION: Panniculitis in dermatomyositis is rare. Histopathologic findings of panniculitis dermatomyositis are identical to those of lupus panniculitis. Therefore, the final diagnosis requires clinic-pathologic correlation.

Treatment of Malignant Cutaneous Adnexal Neoplasms. / Tratamiento de las neoplasias anexiales cutáneas malignas.

Malignant cutaneous adnexal neoplasms form a group of rare, typically low-grade-malignancy carcinomas with follicular, sebaceous, apocrine, or eccrine differentiation or a combination of the first 3 subtypes. Their clinical presentation is usually unremarkable, and biopsy is required to establish the differentiation subtype and the definitive diagnosis. Due to their rarity, no clear consensus has been reached on which treatment is most effective. Mohs micrographic surgery is considered to be the best option to prevent recurrence in the majority of patients. Radiotherapy and chemotherapy have been studied in very few cases and have rarely been shown to be effective.

Detection of human parvovirus B19 DNA in 22% of 1815 cutaneous biopsies of a wide variety of dermatological conditions suggests viral persistence after primary infection and casts doubts on its pathogenic significance.

BACKGROUND: Human parvovirus B19 (B19V) has been associated with a number of dermatological and systemic conditions, including myocarditis and autoimmune syndromes. OBJECTIVES: To determine the frequency of B19V DNA detection in a large dermatopathology practice, and to characterize the histopathological patterns involved. METHODS: We selected for polymerase chain reaction (PCR) detection of B19V a total of 1815 skin biopsies pertaining to entities allegedly related to B19V, as well as cases suspected clinically of representing paraviral exanthemas. Immunohistochemical detection of B19V viral protein 2 (VP2) was performed in 92 PCR-positive cases. RESULTS: B19V DNA was found by PCR in 402 out of 1825 biopsy specimens (22%). VP2 protein was identified by immunohistochemistry in only three instances of papular purpuric 'gloves-and-socks' syndrome. CONCLUSIONS: As the virus has the capacity to persist in different tissues (including the skin) for long periods, it could represent merely an innocent bystander, so no pathogenetic significance can be inferred from the PCR positivity for B19V in the vast majority of dermatological conditions studied.

Update on Frontal Fibrosing Alopecia. / Actualización en alopecia frontal fibrosante.

Frontal fibrosing alopecia (FFA) is an increasingly common acquired primary scarring alopecia, first described by Kossard in 1994. Clinically it is characterized by frontotemporal hairline recession, frequently accompanied by eyebrow loss. FFA was initially thought to have a hormonal origin as it was first described in postmenopausal women and premenopausal women with a history of hysterectomy or early menopause. This origin, however, has been questioned in recent years due to the publication of cases in men and premenopausal women. Although FFA has a highly characteristic clincal pattern, it is histologically similar to lichen planopilaris, and is currently believed to be a clinical variant of this condition. No clinical trials to date have investigated the efficacy of treatments for FFA. Numerous drugs, however, have been assessed in observational studies, and the best results to date have been reported for 5-αreductase inhibitors and intralesional corticosteroids, followed by antimalarials and calcineurin inhibitors. In this article, we review the latest data on the etiology, pathogenesis, clinical presentation, diagnosis, and treatment of FFA.

Amelanotic naevoid melanoma in a 16-month-old albino infant.

Melanoma in individuals with oculocutaneous albinism has been reported in the literature to be rare compared with the more common occurrence of squamous cell carcinoma and basal cell carcinoma. We present a singular case of amelanotic naevoid melanoma arising from a small congenital naevus in a 16-month old albino boy, the youngest reported to date.

Parvovirus B19 infection presenting concurrently as papular-purpuric gloves-and-socks syndrome and bathing-trunk eruption.

Parvovirus B19 infection can cause a wide range of cutaneous manifestations, including papular-purpuric gloves-and-socks syndrome (PPGSS) and petechial bathing trunk eruption. We report a case of an immunocompetent woman with a primary parvovirus B19 infection presenting as concurrent PPGSS and petechial bathing trunk eruption. Parvovirus B19 seroconversion was confirmed several days after the onset of the clinical manifestations. The coexistence of these two cutaneous manifestations of primary parvovirus B19 infection has rarely been reported in the literature. It is important to recognize parvovirus B19 infection early, based on the cutaneous manifestations, to avoid potentially serious systemic complications in susceptible individuals.

Recurrent lipoatrophic panniculitis of children.

BACKGROUND: Recurrent panniculitis in children with lipoatrophy has been loosely described and reported under different names, but has never been systematically evaluated by immunohistochemical stains. OBJECTIVE: To depict the profile of children with recurrent idiopathic panniculitis. METHODS: Study of clinical, histopathological and immunohistochemical features in five cases with recurrent idiopathic panniculitis. RESULTS: Five children with repeated attacks of painful subcutaneous nodules in association with fever, malaise and abdominal pain or arthralgia, with subsequent lipoatrophy were reviewed. In two patients, extensive involvement led to loss of the cutaneous fatty tissue. Laboratory abnormalities included increased acute phase reactants, leukocytosis with mild neutrophilia, microcytic anaemia and elevated liver enzymes. Histopathology showed lobar panniculitis without vasculitis and with a mixed infiltrate, composed of neutrophils, mononuclear cells, lymphocytes, macrophages and myeloid cells. Neutrophils and myeloid cells were more prominent in early lesions, whereas macrophages predominated in late stages, leading to lipophagia and lipoatrophy. Immunohistochemistry showed positive staining for myeloperoxidase around the necrotic adipocytes in early stages and CD68/PGM1 macrophages in late stages. Intense STAT1 staining was observed in the inflammatory infiltrate. All patients improved with methotrexate and corticosteroids. CONCLUSION: We present five cases of lobar panniculitis and lipoatrophy in childhood. The clinico-pathologic presentation shares features with other autoinflammatory diseases.

Clinicopathologic Variants of Mycosis Fungoides. / Variantes clínico-patológicas de micosis fungoide.

Mycosis fungoides (MF) is the most common primary cutaneous T-cell lymphoma. The clinical course of the disease is typically characterized by progression from a nonspecific phase of erythematous macules to the appearance of plaques and ultimately, in some patients, tumors. However, numerous clinical and histopathologic variants of MF with specific therapeutic and prognostic implications have been described in recent decades. Clarification of the differential diagnosis can be frustrated by the wide range of clinical manifestations and histopathologic patterns of cutaneous infiltration, particularly in the early phases of the disease. In this paper, we review the main clinical, histopathologic, and immunohistochemical characteristics of the variants of MF described in the literature in order to facilitate early diagnosis of the disease.