Fig. 2

Variations in INSM1 staining in neuroendocrine lung neoplasms. a Patchy, weak INSM1 staining in small cell lung carcinoma. Most cells are negative. b INSM1 shows a “smeared” pattern in crushed area in small cell lung carcinoma (arrow), distinct from crisp nuclear staining in viable tumor cells (arrowhead). c Typical carcinoid tumor, with very minimal and focal INSM1 staining. d Very focal and weak INSM1 staining in an atypical carcinoid tumor. All images at original magnification x200