While until recently HGSC was thought to arise from simple differentiation of cortical inclusion cysts (CICs) of ovarian surface epithelium (OSE), the cell origin of HGSC is now understood to be much more complex, with evidence for other sites of origin, both intra- and extra-ovarian, having come to light.
A 2007 paper describes the process of determining cell of origin as "Tumour origin is typically assigned to the organ presenting with the dominant tumour mass.