Regarding beta-catenin expression, in well-differentiated thyroid cancers, reactivity is primarily localized in the lateral membrane, whereas in poorly differentiated carcinomas or squamous lineage, reactivity is continuously presented along the cell membrane, called "fishnet pattern," and has a weaker intensity, punctate intracytoplasmic positivity near the nuclei, and nuclear positivity. The gene discussed is CTNNB1; the disease is thyroid cancer.