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Objectives: Universal screening of upper tract urothelial carcinoma (UTUC) for Lynch syndrome by mismatch repair (MMR) protein immunohistochemistry (IHC) has been recommended by some investigators. Herein, we assess this recommendation retrospectively by simulating its performance on a retrospective, unselected cohort of UTUCs, with comparison to the established setting of colorectal and endometrial adenocarcinoma., Methods: We assessed for complete loss of MMR protein (MLH1, MSH2, MSH6, and PMS2) IHC in 74 consecutive cases of UTUC and then tabulated clinical and pathologic factors. MMR findings from same-institution colorectal and endometrial adenocarcinomas were tabulated for comparison., Results: We observed loss of at least one MMR protein in 12% in our UTUC cohort (three MSH2/MSH6, three MSH6 only, one MLH1/PMS2, and two PMS2 only). Of these nine cases (seven males, two females, median age 67 years, five associated with colorectal adenocarcinoma), at least three (4% of the overall cohort) proved to be Lynch syndrome. Overall, MMR loss in UTUC was comparable to colorectal (11%; 50 of 471 cases) and endometrial (12%; 12 of 101 cases) adenocarcinomas., Conclusions: The rate of MMR loss observed in UTUC was comparable to that in the established setting of colorectal and endometrial adenocarcinomas, supporting universal UTUC screening at our institution and others., (© American Society for Clinical Pathology, 2020. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

While adenoid cystic carcinoma is not an uncommon tumor in the salivary glands, its occurrence in the larynx and trachea is rare. Extension of an adenoid cystic carcinoma of the larynx and trachea to the thyroid with manifestation as a thyroid nodule is extremely rare. However, this possibility always should be considered whenever there are cytologic features suggestive of adenoid cystic carcinoma in thyroid aspirates and when there is a history of adenoid cystic carcinoma in the trachea or larynx or in any part of the body.