Carcinoid Tumor

Carcinoid tumors demonstrate a variety of architectural patterns, including nested (insular), trabecular, acinar, and tubular. Multiple patterns often coexist within the same tumor (as seen here). There is no prognostic implications to these patterns. Note the complete absence of cytologic atypia as well as mitotic activity in the tumor cells. Many cells contain clear cytoplasm due to lipid accumulation. Cases where such cells predominate are labeled lipid-rich or clear cell carcinoid.