1. A method for identifying candidate target cells within a biological fluid specimen, comprising: obtaining a biological fluid specimen; preparing the biological fluid specimen by staining cell nuclei in the biological fluid specimen with a first bio-conjugated dye having a first color and configured to bind nucleic acids in the cell nuclei of the target cells, and staining cytoskeletal cell features in the biological fluid specimen with a second bio-conjugated dye having a second color and configured to bind to cytoskeletal cell features of the target cells, and staining white blood cells in the biological fluid specimen with a third bio-conjugated dye having a third color and configured to bind to human leukocyte antigens in the biological fluid specimen; capturing a digital image of the biological fluid specimen, the digital image having a plurality of color channels; and applying image analysis to the digital image including receiving the digital image in a computer, identifying, in the computer, first connected regions of pixels of a minimum first intensity in a first channel of the plurality of color channels, identifying, in the computer, second connected regions of pixels of a minimum second intensity in a second channel of the plurality of color channels, determining, in the computer, first connected regions and second connected regions that spatially overlap, determining, in the computer, an aspect ratio of the spatially overlapping first connected regions and second connected regions based on a color channel of the plurality of color channels, identifying, in the computer, first connected regions and second connected regions that spatially overlap and for which the aspect ratio meets an aspect ratio threshold; determining, in the computer, a second connected region and a third connected region that spatially overlap, determining, in the computer, an intensity ratio of the spatially overlapping second connected region and third connected region based on two color channels of the plurality of color channels, eliminating as a candidate, in the computer, a spatially overlapping first connected region and second connected region corresponding to a spatially overlapping second connected region and third connected region for which the intensity ratio does not meet an intensity ratio threshold, and providing a portion of the image corresponding to a remaining identified spatially overlapping first connected region and second connected region to a classifier as candidates for classification.