Stereological techniques using the optical disectors require estimation of final section thickness, but frozen tissue irregularities may interfere with this estimation. Cryostat slices from rodent nerve tissues (dorsal root ganglia, spinal cord, and brain), cut at 16, 40, and 50 μm, were digitized with a confocal microscope and visualized through 3D software. Geometric section thickness of tissue (Tgeom) was defined as tissue volume/area. Maximal section thicknesses (Tmax), from the top to the bottom of the section, were measured in a random sample of vertical ZX planes. Irregularities were mostly related to blood vessels traversing the tissue and neuronal somas protruding over the cut surfaces, with other neuron profiles showing a fragmented appearance. Irregularities contributed to increasing the distance between the tops and bottoms of slices sectioned in different laboratories. Significant differences were found between Tmax and Tgeom for all thickness studies and counting frames (p<0.01). The Tgeom/Tmax average rate was 68.4–85.7% in volumes around cell profiles (∼600–1,200 μm2) and 83.3–91.8% in subcellular samples (∼25–160 μm2). Confocal microscopy may help to assess tissue irregularities, which might lead to an overestimation of tissue volume if section thickness is estimated by focusing on the top and bottom of the sections.

Andrea et al. were the first to use contact endoscopy in the diagnosis of laryngeal disease, in 1995. This method enables in vivo microscopy of laryngeal mucosa.

In the present study, comparison of contact endoscopy with frozen section histopathology was performed in 142 patients with various diseases of the larynx. Paraffin section histopathology diagnosed 70 benign lesions, 23 precancerous lesions and 49 malignant lesions. Frozen section histopathology showed a sensitivity of 89.8 per cent, a specificity of 98.9 per cent and an accuracy of 95.7 per cent (χ2 = 1.5; p = 0.18). Frozen histopathology diagnosed 45 malignant lesions, including one false positive and five false negative results. Contact endoscopy yielded a sensitivity of 79.59 per cent, a specificity of 100 per cent and an accuracy of 92.95 per cent (χ2 = 8.1; p = 0.002). All malignant lesions diagnosed by contact endoscopy were confirmed by histopathology; contact endoscopy failed to recognise malignant lesions in 10 patients.

Contact endoscopy is preferable to frozen section histopathology as it is noninvasive, provides information on microscopic diagnosis and laryngeal lesion margins, and enables visualisation of the laryngeal mucosa microvasculature. The use of contact endoscopy along with frozen section histopathology improves diagnostic accuracy and allows for operative (or other) therapy to continue according to the results obtained.

Granular cell tumours of the larynx are a very rare cause of persistent hoarse or husky voice in children. We report the case of a 13-year-old girl who presented with a three-year history of progressively huskier voice. We discuss the presentation, location and diagnosis of the tumour. In addition, we present a method of surgical treatment of the tumour, involving the hitherto unreported technique of laser excision and frozen section of the lesion.

Ethanol (ethyl alcohol) has long been a standard reagent used in preparing tissues for light and electron microscopy. After fixation, tissues are usually dehydrated with ethanol before being embedded in paraffin or plastic. In this study we show that the ethanol-infiltrated tissue can be frozen and sectioned directly without embedding. When tissue impregnated with ethanol is cooled below about −117°C with liquid nitrogen, the ethanol solidifies without appreciable crystallization. The frozen tissue can then be sectioned in a commercial cryoultramicrotome that is set at −155 to −170°C to produce semithin frozen sections (0.5 to 3 μm thick) for light microscopy or ultrathin frozen sections (50 to 100 nm thick) for electron microscopy. Sections are picked up and mounted on glass slides or EM grids by means that are in current use for ice ultrathin frozen sectioning. Because there is no apparent freezing damage, the morphology in these ethanol frozen sections of unembedded tissue appears generally quite good, often resembling that obtained by conventional EM techniques. Examples are provided that illustrate the use of this material for immunocytochemistry at the light and electron microscope levels.

Ethanol (ethyl alcohol) has long been a standard reagent used in preparing tissues for light and electron microscopy. After fixation, tissues are usually dehydrated with ethanol before being embedded in paraffin or plastic. In this study we show that the ethanol-infiltrated tissue can be frozen and sectioned directly, without embedding. When tissue impregnated with ethanol is cooled below about -117¡C with liquid nitrogen, the ethanol solidifies without appreciable crystallization. The frozen tissue can then be sectioned in a commercial cryoultramicrotome that is set at -155 to -170°C to produce semithin frozen sections (0.5-3 μm thick) for light microscopy, or ultrathin frozen sections (50-100 nm thick) for electron microscopy. Sections are picked up and mounted on glass slides or EM grids by means that are in current use for ice ultrathin frozen sectioning. Since there is no apparent freezing damage, the morphology in these ethanol frozen sections of unembedded tissue appears generally quite good, often resembling that obtained by conventional EM techniques. Examples are provided that illustrate the use of this material for immunocytochemistry at the light and electron microscope levels.