Medallion‐like dermal dendrocyte hamartoma: A rare congenital CD34‐positive dermal lesion clinically and pathologically overlapping with fibroblastic connective tissue nevus

Both medallion‐like dermal dendrocyte hamartoma and fibroblastic connective tissue nevus are rare benign dermal lesions composed of CD34‐positive spindle cells. Although regarded as different diseases, it is sometimes difficult to distinguish between them due to their clinical and pathological similarities. We present a case of medallion‐like dermal dendrocyte hamartoma that could also be diagnosed as fibroblastic connective tissue nevus and propose the possibility of overlap in these diseases.     

Vascular network tightly enclosing lesions of molluscum contagiosum: Basket‐like capillaries of molluscum

Immunohistochemical studies of one typical and two atypical cases of molluscum contagiosum with anti‐CD34 monoclonal antibodies showed a tightly enclosing fine vasculature around the lesional masses of the disease. The thin interstitial septa between the lobules of the molluscum lesions also contained abundant endothelium. An electron microscopic study of a pinched‐off lesion of common molluscum contagiosum demonstrated that the tightly enclosing blood vessels lacked muscle layers, suggesting that they were capillaries, being a distance of several hundred nanometers from the basal cells of the molluscum mass. A 3D constructed image of the vasculature confirmed a network of the vessels. These tightly enclosing vascular networks around the lesions of molluscum contagiosum support the rapid growth of this disease.     

Erythema multiforme‐like lesions in primary cutaneous aggressive cytotoxic epidermotropic CD8+ T‐cell lymphoma: A diagnostic and therapeutic challenge

Primary cutaneous aggressive cytotoxic epidermotropic CD8+ T‐cell lymphoma is an extremely rare, rapidly progressing, cutaneous lymphoma, with frequent systemic involvement and poor prognosis, that still represents a diagnostic and therapeutic challenge, especially in the early stage. Herein, we report a case of an elderly woman with a fulminant course, who at onset presented with clinical and pathological features mimicking erythema multiforme (EM) and treated with cyclosporine that led to rapid deterioration with fatal outcome 6 months after disease onset. Histopathology showed a lichenoid, epidermotropic and nodular, angiocentric, dermal and subcutaneous infiltrate of sF1, CD8+, CD45RA+ small to medium‐sized atypical lymphoid cells, which strongly expressed cytotoxic markers. Monoclonal T‐cell‐γ receptor was clonally rearranged and array‐CGH showed numerous chromosomal imbalances. This case evidences the clinical, pathological and therapeutic challenges involved in this tumor. The first biopsy showed an interface dermatitis‐like pattern, revealing the deceptive features that early cutaneous infiltrates of this aggressive lymphoma may have. A high suspicion for aggressive CTCL and a low threshold for repeat biopsies should be maintained when faced with rapidly progressing and/or ulcerative EM‐like lesions, especially if immunomodulatory therapy is being considered.     

Plaque‐like myofibroblastic tumor,a rare entity of childhood: Possible pitfalls in differential diagnosis

Plaque‐like myofibroblastic tumor is a rare and benign pediatric soft tissue tumor. It presents as a slowly growing plaque reaching several centimeters in diameter, made up of multiple nodules. The clinical and histological features of this benign entity are similar to other fibrohistiocytic or myofibroblastic tumors occurring in childhood, so the diagnosis can be difficult. The correlation between clinical data, histopathology, and immunohistochemistry is necessary for the correct diagnosis.     

Genital folliculo‐sebaceous cystic hamartoma: A claim of the stroma as a clue in the diagnosis of proliferations with follicular differentiation

Folliculo‐sebaceous hamartomas comprise a series of entities whose boundaries are imprecise. We present the clinical case of a folliculo‐sebaceous cystic hamartoma of genital localization where the diagnosis was established based on the epithelial proliferation, but mostly, on the characteristic stroma. Because this lesion lacked of the cystic component, we mention the most frequent differential diagnoses and review the literature of the few cases published on this infrequent localization.     

Toll‐like receptor 4 attenuates a murine model of atopic dermatitis through inhibition of langerin‐positive DCs migration

Atopic dermatitis (AD) is a common chronic inflammatory skin disease that is often associated with skin barrier dysfunction leading to a higher frequency of bacterial and viral skin infections. Toll‐like receptor (TLR) 4 on resident skin cells was involved in sensing pathogens and eliciting pathogen‐specific innate and adaptive immune responses. Previous studies have demonstrated that TLR4 was linked to AD severity in context of pathogen infection. However, the immune regulatory role of TLR4 in AD remains to be defined. We here investigated the immune regulatory function of TLR4 in AD induced by repeated epicutaneous application of a hapten, 2,4‐dinitrochlorobenzene (DNCB). Our results showed that TLR4‐deficient (TLR4^?/?) mice exhibited more severe AD symptoms than WT mice after DNCB challenge. The DNCB‐treated TLR4^?/? mice also displayed higher expression levels of inflammatory cytokines and stronger Th2 response than WT counterparts. Moreover, the skin expression of thymic stromal lymphopoietin (TSLP), an important potential contributor to allergic inflammation, was significantly elevated in TLR4^?/? mice compared with that in WT mice upon DNCB administration. Furthermore, we demonstrated that the migration of langerin‐positive dendritic cells (DCs) into draining lymph nodes was enhanced in TLR4^?/? mice following DNCB challenge, which is partially dependent on the production of pro‐inflammatory cytokine TNF‐α. Together, these results determined that TLR4 affected the hapten‐induced skin inflammation in the absence of exogenous pathogen infection, suggesting that TLR4 not only regulates infection but also may serve as a modulator of the immune response during AD development.     

Injury modifies the fate of hair follicle dermal stem cell progeny in a hair cycle‐dependent manner

The dermal papilla (DP) is one of two principal mesenchymal compartments of the hair follicle (HF). We previously reported that a population of HF dermal stem cells (hfDSCs) function to regenerate the dermal sheath (DS), but intriguingly also contribute new cells to the adult DP at the onset of anagen hair growth to maintain normal cycling of HFs and support the production of large hair fibres. Here, we asked whether injury altered the behaviour of hfDSCs and their progeny in order to support wound‐induced hair growth (WIHG) and if the response was modulated by hair cycle stage. αSMACreER^T2:ROSA^YFP mice received tamoxifen to label the DS, including hfDSCs. Full‐thickness excisions were made on the dorsal skin during various stages of the hair cycle. The skin was harvested at the subsequent anagen. Interestingly, there was an increase in the magnitude of recruitment of hfDSC progeny into the DP after injury compared to follicles entering natural second anagen. This bias towards a DP fate only occurred when a wound was induced during certain stages of the HC. In summary, injury modifies the fate of hfDSCs progeny, biasing them towards recruitment into the DP, with the hair cycle stage also influencing this response.     

Erysipelas‐like erythema of familial Mediterranean fever syndrome: a case report with emphasis on histopathologic diagnostic clues

We report histopathological findings in a case of familial Mediterranean fever (FMF) syndrome with an erysipelas‐like erythema (ELE). ELE is the only pathognomic cutaneous manifestation of FMF. ELE is characterized by well‐demarcated, tender, erythematous and infiltrated plaques recurring on the same site and resolving spontaneously within 48–72 h. FMF is a monogenic autoinflammatory syndrome highlighted by recurrent fever associated with polyserositis involving mainly the peritoneum, synovium and pleura. FMF results from a mutation of the MEFV gene, which encodes for pyrin, leading to Il‐1β activation and promoting neutrophil migration into the dermis. Histopathological findings in our case showed a sparse superficial perivascular and interstitial lymphocytic infiltrate admixed with some neutrophils, no eosinophils and mild papillary dermal edema. Venules and lymphatics were dilated, though no vasculitis was identified. Neutrophils are the most common cutaneous marker of autoinflammation, and cutaneous manifestations of monogenic autoinflammatory syndromes are represented by the spectrum of aseptic neutrophilic dermatoses. Neutrophils in the presence of recurrent fever and in the correct clinical context of recurrent erysipelas in the same site are a diagnostic clue for FMF.     

Role of macrophage infiltration in successful repigmentation in a new periphery‐spreading vitiligo lesion in a male Japanese patient

Vitiligo is an acquired disorder in which depigmented macules result from mostly autoimmune loss of melanocytes. The initiating process in vitiligo has still been uncertain. Here, we report the case of a 19‐year‐old man with undetermined/unclassified vitiligo with a new periphery‐spreading vitiligo lesion on the right dorsal hand after rigorous sun exposure. Histopathological evaluation showed noticeable infiltration of CD68⁺ macrophages, moderate infiltration of CD3⁺ T cells, little infiltration of CD8⁺ T cells and CD11c⁺ myeloid dendritic cells, HMB45/CD11c double‐positive cells, and Melan‐A/MART1⁺ deposits in the dermis. We surmised that melanocyte‐derived deposits were mostly phagocytosed by CD68⁺ macrophages and were faintly phagocytosed by CD11c⁺ myeloid dendritic cells, referring distribution of CD68⁺ mononuclear cells and melanocyte biomarkers. Complete repigmentation was achieved following topical application of hydrocortisone butyrate propionate 0.1% ointment. We summarize that prompt clearance of debris by macrophages would be essential to an excellent prognosis of complete repigmentation.     

Clinical study on the effects of a cosmetic product on dermal extracellular matrix components using a high‐resolution multiphoton tomograph

Background/purpose: The aim of this study was to demonstrate the effects of selected plant extracts in a cosmetic cream on the dermal network components after a 3‐month treatment using an in vivo multiphoton tomographic device. Methods: Twenty‐four Caucasian women aged between 45 and 65 applied randomly a cosmetic emulsion B containing active ingredients (soy and jasmine) twice a day on one arm and its vehicle A (without active ingredients) on the other arm during 3 months. Measurements were performed on the internal side of the forearm before starting the treatment (T0), after 4 week (T4) and 12 weeks (T12) treatment. Measurements consisted in a multi‐layers acquisitions using a multiphoton tomograph with subcellular resolution. Optical sections (about 6 μm thick) were recorded from 0 to about 200 μm using two different wavelengths: 760 and 820 nm. To compare the series of images and obtain an objective quantification of the signal of second harmonic generation (SHG) and autofluorescence, the method used consisted in taking the integrated brightness of an image (same rectangular area for all images) as a measure of the signal. Following this step a ratio between brightness of images from the area treated with cream A or B and brightness of untreated area was calculated and used as an assessment of treatment efficacy. The parameter used for statistical analysis (variance analysis) is the difference before and after 12 weeks of treatment by either cream A or B of the signal ratios calculated in the upper dermis (118–130 μm) and those from a deeper region of the upper dermis (165–178 μm). Results: Signals (autofluorescence+SHG) of extracellular matrix do not change significantly with time (weeks 0, 4 and 12) when cream A (vehicle with no active ingredient) is applied. Treatment with cream B results in an enhancement in the signal level of extracellular matrix at week 12. The comparison of signals, in both areas (118–130 μm and 160–178 μm), show an higher increase in the deeper region than in the more superficial one for product B while we do not notice any change with product A. Conclusion: The multiphoton tomograph provided excellent high‐resolution images, which describe clearly the different skin layers, single cells and extracellular matrix components in all the 24 volunteers. Statistic analyses reveal a real effect for product B with selected plant extracts, known to increase collagen synthesis. Changes observed are characteristics of modifications in dermal collagen and elastin content. To our knowledge, it is the first time that it was possible to demonstrate in vivo the effect of a cosmetic product on the superficial dermal layer, in a non‐invasive and non‐destructive process, i.e. without cutting the skin.     

Challenges in sarcoidosis and sarcoid‐like reactions associated to immune checkpoint inhibitors: A narrative review apropos of a case

Sarcoidosis and sarcoid‐like reactions (SLRs) may develop in association with various malignancies, as well as in association to certain oncologic drugs, including immune checkpoint inhibitors (ICIs). We aimed to perform a narrative review with regard to the development of ICIs‐associated sarcoidosis or SLRs, and to discuss the corresponding diagnostic and therapeutic challenges raised in this scenario. Apropos of a melanoma patient developing SLRs while treated with ipilimumab and nivolumab, we searched for clinically evident, ICIs‐associated sarcoidosis or SLRs in the English literature. We recorded the oncologic characteristics, including type of malignancy and type of ICI, the phenotypic characteristics of sarcoidosis/SLRs, as well as the impact on immunotherapy. Including our patient, we identified 80 ICIs‐associated sarcoidosis or SLRs cases. Both sexes were equally affected (40 F/40 M) and the most common malignancy was melanoma (65/80, 81.3%). Concerning the oncologic treatment, there was a predilection for pembrolizumab (23/80, 28.7%), followed by the ipilimumab/nivolumab combination (21/80, 26.3%), ipilimumab (18/80, 22.5%), nivolumab (16/80, 20.0%). Although in the majority of the cases (52/80, 65.0%) there was no need for systemic prednisolone for the management of sarcoidosis, a significant proportion of patients finally discontinued ICIs treatment (44/80, 55.0%). Phenotypically, sarcoidosis and SLRs highly imitate oncologic progression posing diagnostic difficulties. A therapeutic dilemma is also raised when there is a need for systemic prednisolone, since the latter may jeopardize the therapeutic efficacy of immunotherapy. Sarcoidosis and SLRs, though rare, can present in oncologic patients treated with ICIs. Clinicians should be aware of this possibility and the related diagnostic and therapeutic challenges they have to face in this scenario.     

Plexiform fibrohistiocytic tumor on the chest of a 5‐year‐old child and review of the literature

Plexiform fibrohistiocytic tumor (PFT) is a rare neoplasm of mesenchymal origin that can be identified by its propensity for children and adolescents combined with a characteristic histologic arrangement of histiocytes and osteoclast‐like giant cells whorled within tumor islands. A 5‐year‐old female presented with a raised, intermittently tender, and slowly enlarging tumor on her chest, which was histologically confirmed to be a PFT. We present this case along with a comprehensive review of PFT cases reported in the literature to describe the demographic, histologic, and rarely metastatic behavior of this entity. It is important to include PFT on the differential diagnosis of an enlarging tumor in the pediatric population.     

Spontaneous occurrence of photoageing‐like phenotypes in the dorsal skin of old SAMP1 mice,an oxidative stress model

Skin photoageing is a complex, multifactorial process and both intrinsic and extrinsic factors may contribute to its pathogenesis. The ultraviolet‐irradiated hairless mouse has been used as an animal model for photoageing, but this model mimics only the ‘extrinsic’ aspects. Here, we show that skin from old SAMP1 mice, a model for higher oxidative stress and senescence acceleration, exhibited histological and gene expression changes similar to those in human photoaged skin without ultraviolet irradiation. These changes include an increase in elastic fibre and glycosaminoglycan histologically, an upregulation of several proinflammatory cytokines and matrix metalloproteinases, and an increase in lipid peroxide. We propose that SAMP1 mice are a spontaneous animal model for photoageing caused by an exaggerated intrinsic mechanism, namely, higher oxidative status. This mouse model is useful to explore the link between oxidative stress and photoageing, and to evaluate the efficacy of antioxidants.