CT , ▁if ▁it ▁is ▁entirely ▁inside ▁the ▁body , ▁may ▁not ▁present ▁for ▁years , ▁until ▁it ▁grows ▁large ▁enough ▁to ▁cause ▁pain , ▁const ip ation ▁and ▁other ▁sympt oms ▁of ▁a ▁large ▁mass ▁inside ▁the ▁pel vis , ▁or ▁until ▁it ▁begins ▁to ▁extend ▁out ▁of ▁the ▁pel vis . ▁ ▁Even ▁a ▁relatively ▁large ▁S CT ▁may ▁be ▁missed , ▁if ▁it ▁is ▁internal , ▁because ▁the ▁b ony ▁pel vis ▁conce als ▁and ▁protect s ▁it . ▁ ▁Med iast inal ▁tum ors , ▁including ▁ter atom as , ▁are ▁similarly ▁conce aled ▁and ▁protected ▁by ▁the ▁rib ▁c age . ▁ ▁Some ▁S CT s ▁are ▁discovered ▁when ▁a ▁child ▁begins ▁to ▁talk ▁at ▁about ▁age ▁ 2 ▁years ▁and ▁compla ins ▁of ▁their ▁bottom ▁hur ting ▁or ▁feeling ▁" po opy " ▁when ▁they ▁ride ▁in ▁a ▁car ▁seat . ▁ ▁Other ▁tum ors ▁can ▁occur ▁in ▁the ▁sac roc oc cy ge al ▁and / or ▁pres ac ral ▁regions ▁and ▁hence ▁must ▁be ▁ruled ▁out ▁to ▁obtain ▁a ▁differential ▁diagn osis . ▁ ▁These ▁include ▁extr asp inal ▁ep end ym oma , ▁ep end ym ob last oma , ▁ne uro blast oma ▁and ▁r hab dom y os ar com a . ▁ ▁Sm aller ▁S CT s ▁with ▁an ▁external ▁component , ▁seen ▁in ▁pr en atal ▁ul tras ounds ▁or ▁at ▁birth , ▁often ▁are ▁mistaken ▁for ▁sp ina ▁b if ida . ▁ ▁C yst ic ▁S CT ▁and