Large and small cell masses are a common feature of paraganglioma cultures.

Cell masses appear to be anchored by fibroblast-like cells to the plastic substrate, and often ‘shed’ cells of chromaffin cell morphology during the first few weeks of culture (A, Tu42_35 days_5% FBS_20x obj. phase contrast). ‘Shed’ cells are often weakly adherent to the plastic or fibroblast underlayer and can be harvested by vigorous pipetting and re-cultured (B, Tu51_58 days _1% FBS_40x obj. phase contrast). These large cell masses consist of numerous synaptophysin-positive cells in the first weeks of culture (C, Tu44_ thoracic PGL_14 days_1% FBS_Syn_20x obj.). Vimentin antibody staining illustrates the general structure of these cell masses (D; Tu44_14 days_1% FBS_Vim_20x obj.). Cell masses often initially express synaptophysin intensely but gradually lose expression and by 4–6 weeks show synaptophysin-expressing cells only in the outermost layer (E, Tu44_4 weeks_5% FBS_Syn_40x obj.) Cells of sustentacular morphology often associate with cell masses when these cells are present in a culture (F, Tu44_4 weeks_5% FBS_GFAP_ 20x obj.). Cell proliferation is ongoing in cell masses (G, Tu44_4 wks_serum-free med_Ki-67_5x obj.) but does not appear to overlap with surviving synaptophysin-positive cells (H, Tu44_4 wks_serum-free med_Synaptophysin_5x obj.; inset Synaptophysin_40x obj.).