Seeking their fourth FA Women's Cup in succession, Arsenal ran in eight goals at Borehamwood with six separate Gunners getting on the scoresheet. Sanderson grabbed two, while Gemma Davison, Kelly Smith, Mary Phillip, Rachel Yankey and Karen Carney all scoring.
An own goal completed the scoring for the home side, while West Ham's consolation strike was one of the finest of the afternoon with Samantha Puttick doing well to lob Arsenal's tall goalkeeper Emma Byrne.
Arsenal are at home again in the Sixth Round, with Birmingham City the opponents in the last eight.
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