Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
cancĕrasco, āvi, 3, v. inch. n. [cancer, III.], to become cancerous, be afflicted with a cancer, to suppurate like a cancer (post-class.; only in perf.), Plin. Val. 1, 10; App. Horb. 36; Marc. Emp. 9.
Hence, cancĕrātus, a, um, cancerous: vulnera, Plin. Val. 4, 32: ulcera, id. ib. 4, 51.