A 44−year−old man underwent a colono− scopic examination for a health evalua− tion. He had no subjective symptoms. A colonoscopy revealed a polypoid lesion 2.0 cm in diameter at the site of the appen− diceal orifice. This lesion had pink−col− ored, normal−appearing mucosa with a smooth surface and a 2−mm central dim− ple (l " Fig. 1). When pushed by a biopsy forceps, the lesion was found to have a hard consistency and could be partially re− duced into the appendiceal base. On the basis of the colonoscopic finding, a pre− sumptive diagnosis of a submucosal tu− mor arising from the appendix was made. An abdominal CT scan showed the pres−

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