A biopsy device comprises a body, a needle, a cutter, and a valve assembly. The needle extends distally relative to the body. The needle defines a first lumen and a second lumen. The first and second lumens extend along a first and second longitudinal axis, respectively. The needle includes an opening fluidly coupling the first and second lumens. The cutter is translatable relative to the needle. The valve assembly comprises a vent opening and a spool body. The spool body is movable relative to the vent opening between a first and second position. The second lumen is coupled to the vent opening when the spool body is in the first position. The second lumen is sealed relative to the vent opening when the spool body is in the second position. The spool body is configured to transition between the first and second position by translation of the cutter.
