Collision tumor of primary malignant lymphoma and adenocarcinoma in the colon diagnosed by molecular pathology: A case report and literature review

Figure 3 Microscopic examination and immunohistochemistry. A: Histopathology of one component of the mass was a moderately differentiated adenocarcinoma having a mucinous component arising from a tubulovillous adenoma (top) (Hematoxylin and eosin (HE), original magnification 20×); B: Adenocarcinoma invaded the muscularis propria (HE, original magnification 100×); C: The other component was diffusely medium-to-large lymphocytes, with uniform morphology, frequent mitosis and obvious cell atypia (HE, original magnification 400×); D: Immunohistochemistry of adenocarcinoma was strongly positive for cytokeratin (black arrow), while the atypical lymphocytes were negative (orange arrow) (EnVision method, original magnification 20×); E: Immunohistochemistry of the atypical lymphocytes was strongly and diffusely positive for CD20 (EnVision method, original magnification 200×); F: Immunohistochemistry of the atypical lymphocytes was negative for CD3 (EnVision method, original magnification 200×).