Preoperative imatinib is used frequently in the treatment of large localized GISTs to shrink the tumor prior to surgery. This approach may lead to challenges in the estimation of the risk of recurrence and the need of adjuvant imatinib, because the diagnosis is usually made from a needle biopsy with scant tissue for the assessment of GIST mitotic activity, a key prognostic factor. We propose a mitosis count multiplication method as a proxy for estimating the tumor mitotic count in select cases.