The word cankerworms is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 25
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (48 words)
anomers, cankers, canoers, coakers, coarsen, coarser, conkers, corkers, corneas, corners, crakers, cranker, crewman, croaker, enamors, knowers, markers, marrows, moaners, mockers, narrows, oarsmen, rackers, rancors, rankers, reckons, recorks, recrown, remarks, reracks, reswarm, rewarms, reworks, roamers, rockers, romance, scorner, seaworm, seaworn, smacker, swanker, swarmer, warmers, warners, workers, workman, workmen, wormers