Human polyomavirus 7 (HPyV7) is one of 11 HPyVs recently discovered through genomic sequencing technologies. Two lung transplant recipients receiving immunosuppressive therapy developed pruritic, brown plaques on the trunk and extremities showing a distinctive epidermal hyperplasia with virus-laden keratinocytes containing densely packed 36-45-nm icosahedral capsids. Rolling circle amplification and gradient centrifugation testing were positive for encapsidated HPyV7 DNA in skin and peripheral blood specimens from both patients, and HPyV7 early and capsid proteins were abundantly expressed in affected tissues. We describe for the first time that HPyV7 is associated with novel pathogenicity in some immunosuppressed individuals.

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Primary carcinoid tumor of the skin (PCTS) is an uncommon indolent neoplasm, with 10 cases described in the literature. The tumors affect patients in the sixth to ninth decades of life (mean = 66.3 years) with an equal gender distribution and predilection for the head and trunk. They present as slowly enlarging nodules of variable duration, ranging from 1 to 60 years (mean = 11.4 years). PCTS is characterized by architectural, cytomorphologic, ultrastructural, and immunohistochemical features typical of a low-grade neoplasm with neuroendocrine differentiation. PCTS typically follows a benign clinical course and therefore has to be distinguished from cutaneous metastases of visceral carcinoid tumors, which herald dissemination of malignancy and poor prognosis. While the distinction from other histologically similar entities can be achieved by histopathological examination, PCTS can be distinguished from a visceral metastasis only by a judicious clinicopathologic correlation. Herein we describe the clinical presentation, histological appearance, and management of these tumors.

Well-differentiated neuroendocrine tumors metastasize to the skin uncommonly, and only 35 cases are reported in the literature. In only five of these patients, cutaneous metastases were the presenting symptom of malignancy; herein we report four such cases. Two patients were female and two male, aged 50 to 74 years (mean: 64.5 years), each with a solitary painless, slowly-enlarging, non-ulcerated cutaneous nodule of 3 to 12 months duration (mean: 9 months). The lesions were on the scalp (n=3) and trunk (n=1), and ranged in greatest dimension from 0.5 to 2.5 cm. The distinction from other microscopically similar entities, and the interpretation of origination from gastrointestinal, pancreatic or respiratory system primaries, was made clinically, or was based on the morphologic features and the immunohistochemical profile. One patient died of the disease progression after 36 months while two patients are alive with significant disease progression after 24 and 60 months. Metastatic neuroendocrine tumor should be considered in the differential diagnosis of cutaneous tumors with neuroendocrine morphology even in patients with no known history of visceral malignancy.

Atopic dermatitis (AD) often presents more severely in African Americans (AAs) and with greater involvement of extensor areas. To investigate immune signatures of AD in AAs with moderate to severe pruritus, lesional and non-lesional punch biopsies were taken from AA patients along with age-, race-, and sex-matched controls. Histology of lesional skin showed psoriasiform dermatitis and spongiotic dermatitis, suggesting both Th2 and Th17 activity. Gene Set Variation Analysis showed upregulation of Th2 and Th17 pathways in both lesional versus non-lesional and lesional versus control (p < 0.01), while Th1 and Th22 upregulation were observed in lesional versus control (p < 0.05). Evidence for a broad immune signature also was supported by upregulated Th1 and Th22 pathways, and clinically may represent greater severity of AD in AA. Furthermore, population-level analysis of data from TriNetX, a global federated health research network, revealed that AA AD patients had higher values for CRP, ferritin, and blood eosinophils compared to age-, sex-, and race-matched controls as well as white AD patients, suggesting broad systemic inflammation. Therefore, AA AD patients may feature broader immune activation than previously thought and may derive benefit from systemic immunomodulating therapies that modulate key drivers of multiple immune pathways.

Desmoplastic trichoepithelioma (DTE) is a benign follicular tumor occurring most commonly within facial skin of young and middle-aged women, morphologically characterized by a superficial dermal proliferation of basaloid cells growing in narrow strands embedded in a desmoplastic stroma associated with small keratinizing cysts. DTE must be distinguished from other benign epithelial proliferations such as syringoma, microcystic adnexal carcinoma and infiltrating basal cell carcinoma. Among morphological features useful in that distinction, perineural involvement is considered a feature indicative of malignancy. We present a series of seven DTEs with otherwise typical presentation and morphology, nevertheless showing epithelium present in the perineural spaces of adjacent small dermal nerves. Patients ranged in age from 14 to 66 years (mean 44 years). All seven tumors were restricted to dermis, showed strands of basaloid epithelium in desmoplastic stroma and contained CK20-positive cells. Additionally, five of five examined tumors displayed diffuse expression of p75 neurotrophin receptor. Five patients were followed up clinically (follow-up time range: 2 months-4 years). No tumor recurrence was observed in any of these patients. We postulate that perineural involvement is an unusual feature of DTE that should not be equated with malignancy or lead to unnecessary over-treatment.

Our findings indicate that DP is sufficient for primary diagnosis in inflammatory dermatopathology. Higher magnification scanning may be required to identify submicron features, such as microorganisms. Subtle differences in image quality between these 2 modalities may contribute to varied histologic interpretations of which pathologists should be aware when validating clinical DP systems.