Intermediate Filament Typing vs. Electron Microscopy in the Diagnosis of Major Tumor Types in Fine Needle Aspirates

Abstract

In aspiration cytology, the accuracy of diagnosis of tumor type depends on the expression of morphologic signs of differentiation of tumor cells at the light microscopic level and on the availability of reliable clinical, radiological, and other relevant information. If differentiation of tumor cells in fine needle aspirate (FNA) is clearly expressed, the specific diagnosis of major tumor type such as carcinoma, sarcoma, malignant lymphoma, or malignant melanoma can easily be made by an experienced cytopathologist [21]. However, the diagnosis of tumor type in FNA has its limitations. If perceptible morphologic features of differentiation of tumor cells are absent, the “descriptive tumor typing” is of little use. This is supported by poor interobserver reproducibility among several cytopathologists in the diagnosis of tumor type in difficult aspirates with no detectable features indicating differentiation of tumor cells [9] and also by poor interobserver agreement as to malignant cell types [36]. In such cases, “histogenetic tumor typing” based on information provided by differentiation or tissue-specific markers, when combined with analysis of morphology of tumor cells and clinical data can markedly improve cytologic diagnosis of tumor type in FNA [9, 12, 14, 19]. In aspiration cytology such information can be obtained by exploiting monoclonal antibodies (MAbs) to intermediate filaments (IF) [2, 3, 6–14, 33] and to other cell antigens [18,19, 28] as well as by transmission electron microscopy (EM) [1, 4, 5, 16, 20, 24–26, 30, 34, 37].