Zellballen pattern seen in:

Zellballen pattern: Contain nest of sustentacular cells & chief cells with pale eosinophilc staining Seen in tumors of chromaffin cells, i.e pheochromocytoma & Paraganglioma (carotid body tumor). Most common location of these tumors is within adrenal medulla,where they give rise to pheochromocytomas & approximately 70% of extra-adrenal paragangliomas occur in head & neck region.