<prompt> Zellballen pattern is seen in?PheochromocytomaSchwannomaAcoustic neuromaTransistional renal cell carcinoma  <response>: Ans. is a i.e., Pheochromocytoma Pheochromocytoma is composed of polygonal to spindle shaped chromaffin cells or chief cells, clustered with sustentacular cells into small nests or alveoli zellballen by a rich vascular network. The nuclei are usually round to ovoid, with a stippled salt pepper chromatin that is characteristic of most neuroendocrine tumors. Zellballen pattern is also seen in paraganglioma. 