Collagenous gastritis is a rare condition defined histologically by a superficial subepithelial collagen layer. This study further characterizes the morphologic spectrum of collagenous gastritis by evaluating a multiinstitutional series of 40 patients (26 female and 14 male). The median age at onset was 16 years (range 3-89 years), including 24 patients (60%) under age 18. Twelve patients (30%) had associated celiac disease, collagenous sprue, or collagenous colitis. Hematoxylin and eosin slides were reviewed in biopsies from all patients and tenascin, gastrin, eotaxin, and IgG4/IgG immunohistochemical stains were applied to a subset. The distribution of subepithelial collagen favored the body/fundus in pediatric patients and the antrum in adults. There were increased surface intraepithelial lymphocytes (425 lymphocytes/100 epithelial cells) in five patients. Three of these patients had associated celiac and/or collagenous sprue/colitis, while the remaining two had increased duodenal lymphocytosis without specific etiology. An eosinophil-rich pattern (430 eosinophils/high power field) was seen in 21/40 (52%) patients. Seven patients' biopsies demonstrated atrophy of the gastric corpus mucosa. Tenascin immunohistochemistry highlighted the subepithelial collagen in all 21 specimens evaluated and was a more sensitive method of collagen detection in biopsies from two patients with subtle subepithelial collagen. No increased eotaxin expression was identified in 16 specimens evaluated. One of the twenty-three biopsies tested had increased IgG4-positive cells (100/high power field) with an IgG4/IgG ratio of 55%. In summary, collagenous gastritis presents three distinct histologic patterns including a lymphocytic gastritis-like pattern, an eosinophil-rich pattern, and an atrophic pattern. Eotaxin and IgG4 were not elevated enough to implicate these pathways in the pathogenesis. Tenascin immunohistochemistry can be used as a sensitive method of collagen detection.

Blastomycosis-like pyoderma is a form of pyoderma with variable clinical findings and histopathological features. We present a case series of 39 patients collected over a 35-year period to demonstrate its clinical features and histological findings. The most common clinical presentations found were solitary plaques, solitary nodules, sinuses, crypts, verrucous plaques and discharge, usually on sun-exposed skin. The most common histopathological findings were chronic granulomatous inflammation, suppurative inflammation, sinus and abscess formation, pseudoepitheliomatous hyperplasia, transepidermal elimination and scarring. We discuss its treatment and the recent literature that has focused on its response to acitretin.

Acne necrotica is a disorder of adults of obscure aetiology, featuring repeated cropping of inflammatory papulonodules which rapidly necrotise, leaving varying degrees of superficial scarring with pathological features in early lesions of a necrotising lymphocytic folliculitis. A perceived diminishing interest in this entity in recent years prompted a prospective study of patients presenting to a dermatology practice over a 3-year period to reassess the prevalence of this disorder in general dermatological patients, leading to the identification of 47 patients (35 female) with features of acne necrotica, with histopathology undertaken in atypical cases. We identified the importance of the recognition of primary lesions (1-2 mm umbilicated erythematous papules), often difficult to find in excoriated areas, as being paramount in the diagnosis both clinically and histologically in our study, which reveals a significantly more prevalent and clinically diverse disorder than featured in previous textbook and academic journal descriptions.

Background: Digital multiplex gene expression profiling is overcoming the limitations of many tissue-processing and RNA extraction techniques for the reproducible and quantitative molecular classification of disease. We assessed the effect of different skin biopsy collection/storage conditions on mRNA quality and quantity and the NanoString nCounter™ System's ability to reproducibly quantify the expression of 730 immune genes from skin biopsies. Methods: Healthy human skin punch biopsies (n = 6) obtained from skin sections from four patients undergoing routine abdominoplasty were subject to one of several collection/storage protocols, including: i) snap freezing in liquid nitrogen and transportation on dry ice; ii) RNAlater (ThermoFisher) for 24 h at room temperature then stored at − 80°C; iii) formalin fixation with further processing for FFPE blocks; iv) DNA/RNA shield (Zymo) stored and shipped at room temperature; v) placed in TRIzol then stored at − 80°C; vi) saline without RNAse for 24 h at room temperature then stored at − 80°C. RNA yield and integrity was assessed following extraction via NanoDrop, QuantiFluor with RNA specific dye and a Bioanalyser (LabChip24, PerkinElmer). Immune gene expression was analysed using the NanoString Pancancer Immune Profiling Panel containing 730 genes. Results: Except for saline, all protocols yielded total RNA in quantities/qualities that could be analysed by NanoString nCounter technology, although the quality of the extracted RNA varied widely. Mean RNA integrity was highest from samples that were placed in RNALater (RQS 8.2 ± 1.15), with integrity lowest from the saline stored sample (RQS < 2). There was a high degree of reproducibility in the expression of immune genes between all samples with the exception of saline, with the number of detected genes at counts < 100, between 100 and 1000 and > 10,000 similar across extraction protocols.

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