I recently reviewed the topic of "hepatoid lung adenocarcinomas" and came across this excellent recent article by @natasharekhtman. Interestingly, a few days later I think I found a case of solid and granular adenocarcinoma of the lung metastasizing to mediastinal lymph nodes. This case indeed has a STK11 mutation and has a very aggressive presentation. Hep_Par1 is diffusely positive, TTF-1 is negative and mucicarmine highlights intracellular mucin. The current case illustrates the increasingly recognized overlap between hepatoid adenocarcinoma of the lung and the recently described entity of pulmonary solid and granular adenocarcinoma expressing HepPar-1/CPS1. Historically, diffuse HepPar-1 expression and granular eosinophilic cytoplasm have been interpreted as evidence of hepatoid differentiation; however, emerging evidence suggests that such findings may instead reflect mitochondrial adaptation and metabolic reprogramming, particularly in STK11-altered pulmonary adenocarcinomas. As a result, tumors that would previously have been classified as hepatoid adenocarcinoma may represent a biologically distinct subset of primary lung adenocarcinomas. This distinction is particularly challenging in small biopsies and cytology specimens, where architectural features are limited and HepPar-1 expression may be overinterpreted as evidence of hepatocellular differentiation. The presence of intracellular mucin and the absence of more specific hepatocellular markers in the current case support consideration of this emerging category and underscore the importance of integrating morphology, immunohistochemistry, molecular findings, and clinical-radiologic correlation when rendering a final diagnosis. #lungpathology #thoracic #patholgy @USFpathology sciencedirect.com/science/ar…

Case of the week, of course just before leaving for USCAP: Elderly male with a large right hilar mass and a separate spiculated smaller right lower lobe mass. Any suggestions based on the histologic sections (of the right lower lobe mass)? Clue: this is not a carcinoma, and the classic description of the neoplastic cells rhymes with “twister.” Final diagnosis will be shared after USCAP. #lung #pulmonary #pathology #lungpath #pulmpath #moffitt #meded #pathtwitter #raretumor @USFpathology @DrBuiPathology @rezaesh58