Fourier domain Optical coherence microscopy (FDOCM) offers excellent sensitivity and high axial resolution to image the structure of biological tissue. The depth information is extracted in parallel and allows very high volume acquisition rates. An illumination scheme employing an axicon lens produces a Bessel-like interference pattern to obtain a laterally highly confined illumination needle, extending over a long axial range. High lateral resolution is provided over an extended depth of field (xf). For increased efficiency, the detection occurs decoupled from the illumination, avoiding a double pass through the axicon. The achieved xf-OCM signal reveals the spatial distribution of changes of the refractive index in the sample with high contrast and constant near isotropic resolution of about 2μm. First tomograms of mouse pancreas show a high contrast between the exocrine tissue and the endocrine islets without any labeling or staining. The tissue vascularization and the lobular exocrine architecture are also clearly imaged. Images acquired with classical microscopy techniques, involving stained and fluorescent samples, validate these structures and emphasize the high contrast of the tomograms. It is comparable to the contrast achieved with classical techniques, but employing neither staining, labeling nor slicing of the samples, stressing the high potential of xf- OCM for minimally invasive in vivo small animal imaging.