Open excision of anorectal tumor at time of colonoscopy

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I'm not sure about the coding of this anorectal mass (tumor) that was done at time of colonoscopy.

The Olympus video colonoscope is introduced and advanced through a tortuous sigmoid, identifying diverticula. The instrument was then advanced to the cecum. The instrument was then withdrawn, identifying no other pathology until the rectal mass was identified. I first attempted to excise the mass using snare electrocautery through the colonoscope. This proved inadequate. I then prepped the perirectal area with Betadine, draped off with sterile towels, and then using sterile technique infiltrated around the base of the tumor with Xylocaine. The tumor was then excised using the Harmonic Scalpel. Bleeding was minimal. Hemostasis was judged complete. The resolving defect was then closed with 2-0 chromic.

Because this lesion was not removed by cautery or snare during the colonoscope and was instead excised using scalpel, I'm not sure of the coding.

Thank you!