Pittman, Meredith E.

Objectives Misplaced epithelium in adenomas can occasionally be difficult to distinguish from invasive adenocarcinoma. We evaluated interobserver variability in the assessment of left-sided colon polypectomies for pseudoinvasion versus invasive adenocarcinoma and further investigated relevant histological findings. Methods 28 consecutive left-sided colon polyps with the keywords “pseudoinvasion”, “epithelial misplacement”, “herniation”, “prolapse” or “invasive adenocarcinoma” were collected from 28 patients and reviewed by eight gastrointestinal pathologists. Participants assessed stromal hemosiderin, lamina propria/eosinophils surrounding glands, desmoplasia, high grade dysplasia/intramucosal adenocarcinoma and margin status and rendered a diagnosis of pseudoinvasion, invasive adenocarcinoma, or both. Results Agreement among pathologists was substantial for desmoplasia (κ=0.70), high grade dysplasia/intramucosal adenocarcinoma (κ=0.66), invasive adenocarcinoma (κ=0.63) and adenocarcinoma at the margin (κ=0.65). There was moderate agreement for hemosiderin in stroma (κ=0.53) and prolapse/pseudoinvasion (κ=0.50). Agreement was low for lamina propria/eosinophils around glands (κ=0.12). For invasive adenocarcinoma, seven or more pathologists agreed in 24 of 28 cases (86%), and there was perfect agreement in 19/28 cases (68%). For pseudoinvasion, seven or more pathologists agreed in 19 of 28 cases (68%), and there was perfect agreement in 16/28 cases (57%). Conclusion Moderate to substantial, though imperfect, agreement was achieved in the distinction of pseudoinvasion from invasive carcinoma.

Malakoplakia is an inflammatory process related to defective macrophage response to bacterial infection. To further characterize the clinicopathologic manifestations of gastrointestinal malakoplakia, 26 cases were identified from 6 institutions. Hematoxylin and eosin-stained slides and available stains were reviewed, and pertinent clinicopathologic features analyzed. Sixteen patients were women (62%). Mean patient age was 64 (range: 24 to 83). Sites included the colorectum (n=23), appendix (n=1), and stomach (n=2). Clinical indications for tissue procurement included screening (n=14), tumor resection (n=5), diarrhea (n=1), adenoma surveillance (n=1), ulcerative colitis flare (n=1), abdominal pain (n=1), and appendicitis (1). All cases featured histiocytes with abundant, pale, eosinophilic cytoplasm focally containing Michaelis-Gutmann bodies. The process frequently involved the mucosa (n=19), with architectural distortion in 13 cases. Lymphoid aggregates were present in 18 cases, which were prominent or obscuring in 11 (all colon biopsies) and provoked concern for lymphoma in 2. Associated findings included adenocarcinoma (n=5), adenoma (n=2), gastric hyperplastic polyps (n=1), chemical gastritis (n=1), collagenous colitis (n=1), and active chronic colitis (n=2). In cases with available stains, Michaelis-Gutman bodies were highlighted by Periodic Acid-Schiff with diastase, Von Kossa, and iron stains. Although 2 cases were positive for Tropheryma whipplei antibody, no T. whipplei transcripts were detected on real-time polymerase chain reaction. All patients with available follow-up are alive and well with no additional instances of malakoplakia. Malakoplakia of the gastrointestinal tract is a benign, incidental finding. Although histologic features in the stomach and colon resections are similar to those at other sites, exuberant lymphocytic response in colon biopsies and immunoreactivity with T. whippleii antibody may provoke initial confusion and lead to unnecessary time and resource investment.

Selective internal radiation therapy with 90Y-TheraSphere or 90Y-SIRSphere is used in the treatment of unresectable hepatic malignancies. To the best of our knowledge, this is the first 90Y-TheraSpheres series. BTG International Canada Inc. provided nonradiated microspheres from the Nordion manufacturer. The histologic processed microspheres were colorless, refractile, polarizable, 20 to 30 μm in diameter, and an occasional internal bulls’-eye seen with the condenser out and an internal cross seen with polarized light. Identical microspheres were identified in 15 hepatectomy specimens from four centers between February 2016 and March 2018. The patients were usually male (male=10, female=5) with a mean age of 59 years. All patients had a prior diagnosis of hepatocellular carcinoma (HCC) and documented 90Y-TheraSphere (mean duration from last deployment=32 wk). All surgical pathology specimens in these 15 patients were reviewed, but the microspheres were only identified in the hepatectomy specimens. During manuscript preparation, one case of 90Y-TheraSpheres gastritis was prospectively identified from a separate patient with a history of HCC and 90Y-TheraSpheres. In conclusion, recognition of 90Y-TheraSpheres is important so that one may consider the possibility of a nearby malignancy and or establish the cause of the background inflammatory or radiation-related injury. These structures can be easy to miss because the subtle morphology is distinct from previously reported 90Y-SIRSphere. Clues to the diagnosis include a history of HCC and background radiation change. We report the characteristic morphology as microspheres that overlap in size with 90Y-SIRSphere, but can be differentiated based on 90Y-TheraSpheres’ colorless appearance with occasional internal bulls’-eyes with the condenser out and an internal cross with polarized light.