p53 IHC can help confirm a diagnosis of esophageal squamous dysplasia. In occasional HPV-associated cases, p16 staining is strongly reactive. This example is probably driven by a TP53 mutation. Don't expect the full thickness staining typical of glandular dysplasia.

This week, I learned not only that gangliocytic paragangliomas were reclassified by the WHO as composite gangliocytoma/neuroma and neuroendocrine tumor (CoGNET) - thank you Rhonda Yantiss - but also that they can express CD117/KIT to result in wrong diagnoses on small biopsies.

An incredible esophageal adenosquamous carcinoma arising in Barrett eosphagus with high-grade dysplasia. #UMiamiPath

This gallbladder showed high-grade dysplasia, both flat (not shown; Biliary Intra-epithelial Neoplasia/BilIN), and polypoid (intracholecystic papillary neoplasm), but no invasive carcinoma. Note the abrupt transition between non-dysplastic epithelium and dysplasia. #UMiamiPath

Claudin 18.2 immunohistochemistry is new for gastric and esophageal adenocarcinomas. Benign gastric mucosa is the internal positive control. 2+-3+ membrane staining in ≥75% of tumor cells is the cutoff for use of anti-CLDN18.2 (zolbetuximab). #UMiamiPath PMID: 39098518.

A stunning example of a giant condyloma; this one was probably human papilloma virus (HPV) 6 driven - in situ hybridization using an HPV6/11 cocktail was reactive. #umiamipath

This patient's esophageal samples showed extensive herpes simplex virus viral cytopathic changes. Candida esophagitis is seen in cells that are also infected with the virus. #umiamipath