LONG‐TERM FOLLOW UP OF PATIENTS WITH SMALL GASTROINTESTINAL STROMAL TUMORS IN THE STOMACH USING ENDOSCOPIC ULTRASONOGRAPHY‐GUIDED FINE‐NEEDLE ASPIRATION BIOPSY

Background: Gastrointestinal stromal tumors (GIST) are one of the most common mesenchymal tumors of the gastrointestinal tract. GIST are defined by positive immunohistochemical staining for KIT or CD34 and thus are generally diagnosed after surgery. Because small GIST are rarely diagnosed before surgery, the clinical course of these small tumors is not clear. The aim of the present study was to follow changes in size and configuration of small GIST that were pathologically confirmed using endoscopic ultrasonography‐guided fine‐needle aspiration biopsy (EUS‐FNAB). Methods: Between July 1997 and December 2003, 16 tumors in 16 patients (10 men and 6 women) with an immunohistochemical diagnosis of GIST were regularly followed in our hospital. The median patient age when EUS‐FNAB was performed was 62 years (range 26–82 years) and the median follow‐up period was 4.9 years (range 0.5–9.6 years). Results: Fourteen tumors showed no remarkable changes in size and shape during follow up compared with the initial diagnosis. Two tumors enlarged: one tumor approximately doubled its diameter in 8 years and the other tumor increased from 1.8 cm at diagnosis to up to 10 cm after only 2 years. Doubling time of the latter tumor was calculated as 3.1 months. Conclusions: We conclude that EUS‐FNAB might be a good modality for final diagnosis of GIST without surgery, and that GIST without rapid growth on follow up can be endoscopically followed.     

A method for studying the three-dimensional structure of organs and tissue in pathology]

A new technique of scanning electron microscopy for visualization of hidden cellular surfaces in organs and tissue has been developed. It employs the sample incubation in 30% potassium hydroxide and 96% alcohol mixed in equal amounts and dissociation until single cells appear in the solution, this being checked under phase-contrast microscope. The method is beneficial in non-standard cases of three-dimensional organization of organs and tissues.     

A simple non-iterative procedure for fitting of multiexponential functions.

An efficient procedure for finding parameters of multiexponential function from experimental data is described. All time-constants are determined by roots of the corresponding characteristic polynomial and weighting factors are then found from the system of linear equations. Due to the non-iterative character of the fitting procedure it is fast and does not need a guess about the initial values of parameters of multiexponential function. For single- or double-exponential fitting explicit algorithms are given, for which programming is straightforward.