41-year-old male with a pituitary mass.

Cranial coronal T1-weighted magnetic resonance imaging with contrast enhancement showed a sellar irregular lesion (Figure A). Hematoxylin and eosin staining showed two different morphologies. The majority of tumor cells had medium-sized to large cells with a high nucleus to cytoplasm ratio, vesicular nuclei with prominent nucleoli, and poor adhesion (Figure B), which revealed positive expression of CD20 by Immunohistochemistry (Figure C). The other component showed abundant cytoplasm, spindle-like to ovoid nucleus and rare mitotic figures (Figure D). These tumor cells were positive for Pit-1 (Figure E) and perinuclear punctated structures immunopositive for CK18 (Figure F).