Key Points Question What is the current state of the US pathologist workforce compared with the Canadian pathologist workforce? Findings In this cross-sectional study, a 17.53% decrease in the number of US pathologists was identified from 2007 to 2017. During the same period, there was a 20.45% increase in the number of Canadian pathologists. Meaning Adjusted for population, the US pathologist workforce is now smaller relative to other countries that have experienced major adverse events in clinical laboratory quality and delays in diagnosis.

Sclerosing cholangitis can be primary (PSC) or secondary. One unusual cause of secondary sclerosing cholangitis is the newly recognized entity of IgG4-associated cholangitis. The prevalence and significance of IgG4 plasma cells in patients, who are clinically and radiologically classified as PSC, however, are unknown. Clinical information and histology of liver explants of 98 consecutive liver transplants performed for PSC were reviewed. IgG4 immunohistochemical stain was performed on sections from hilar areas that contained large bile ducts and corresponding cholecystectomy specimens (available in 74 cases). Serum IgG4 levels were measured in stored serum from 81 cases. Tissue IgG4 positivity (>or=10 IgG4+ plasma cells/high power field) was correlated with clinical features (age, sex, presence of inflammatory bowel disease and cholangiocarcinoma, pancreatogram, PSC duration, PSC recurrence after transplant, and number of acute rejection episodes) and histologic findings (periductal lymphoplasmacytic infiltrate, storiform fibrosis, and obliterative phlebitis) in the liver explants. Twenty-three (23%) liver explants showed periductal infiltration with IgG4+ plasma cells. Eighteen cases (22%) had elevated serum IgG4 levels, including 8 without tissue IgG4 positivity. All cases showed dense periductal fibrosis; none had storiform fibrosis or obliterative phlebitis. IgG4 positivity in the liver strongly correlated with moderate-to-marked periductal lymphoplasmacytic inflammation (P=0.002). Clinically, IgG4 positivity in tissue, but not in serum, was correlated with shorter PSC duration before transplant and higher risk of recurrence after transplant. Nearly one quarter of explanted livers that carry a clinical diagnosis of PSC contain increased IgG4+ periductal plasma cell infiltrates and positive serum IgG4 levels. However, none of the explants show histologic features diagnostic of IgG4-associated cholangitis. PSC with tissue IgG4 positivity has a more aggressive clinical course manifested by shorter time to transplant and a higher likelihood of recurrence than IgG4 negative PSC.

Collagenous gastritis (CG) characterized by the deposition of a subepithelial collagen band and accompanying inflammatory infiltrate is a rare disorder. The natural history and pathogenesis of CG remain unclear. We describe the histologic features (23 gastric, 18 duodenal, and 4 colonic biopsies) and clinical findings of an additional 12 cases. Histologic features including active or chronic inflammation, surface epithelial injury, intraepithelial lymphocytosis, intestinal metaplasia, and Helicobacter pylori, and measurement of thickness of subepithelial collagenous band were evaluated in gastric biopsies. The clinical features, endoscopic findings, and follow-up were obtained and correlated with histologic features. There was an even number of males (n=6) and females (n=6). Four patients were children/young adults, 3 of whom (75%) presented with anemia and gastric nodularity. Eight patients were adults, 6 of whom (75%) had an associated autoimmune disease (1 with Hashimoto thyroiditis and polymyositis) or other intestinal disease (3 with celiac sprue, 1 with collagenous colitis, 1 with collagenous sprue), in contrast to none in the 4 children/young adults, P=0.06. The range of subepithelial collagen thickness was 15 to 120 microm in CG. The collagenous layer showed surface epithelial injury and entrapped inflammatory cells. On presentation, the thickened collagen distribution in the antrum and body was variably patchy and diffuse. Four (33%) patients showed lymphocytic gastritis (3 within the same biopsy); one of these patients also had celiac sprue and another had collagenous sprue. Three (25%) patients had celiac sprue (2 had duodenal biopsy proven and 1 had a clinical diagnosis of celiac sprue). An additional patient had duodenal biopsies showing collagenous sprue. Four patients had follow-up biopsies during a 3 to 119-month period after the diagnosis of CG. CG persisted on the follow-up gastric biopsies in 3 (75%) of the 4 patients, and the other patient had lymphocytic gastritis, a finding not seen in previous biopsies. CG is a rare disorder with a distinct presentation and association in pediatric and adult patients. An absence of associated intestinal and autoimmune diseases characterizes the pediatric population. Association with lymphocytic gastritis, celiac or collagenous sprue, collagenous colitis, and autoimmune disorders are frequently seen in adult patients.

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Context.—The pathologist plays the leading role in distinguishing pseudoneoplasms from truly neoplastic lesions in the gastrointestinal tract. Objective.—This review was conducted to heighten awareness of pseudoneoplasms, to help differentiate among the various types of pseudoneoplasms, and to help distinguish pseudoneoplasms from malignancies. Data Sources.—This review is based on the medical literature on pseudoneoplasms in MEDLINE and the authors' own experiences. Reference lists of retrieved articles were also reviewed to identify additional articles. Conclusions.—A classification of pseudoneoplasms, according to the mechanism of injury to the gastrointestinal tract, morphologic patterns, and heterotopia, may be useful in providing a diagnostic framework in which ancillary techniques often have a diagnostic role. Several pseudoneoplasms may be closely associated with true neoplasms (eg, malakoplakia, prolapsetype lesions) because of the nonspecific nature of the response of the intestine to injury.