Abstract
Maintaining proper patient identity during processing of histologic samples is critical. Cross-contamination from one patient to another can occur at any and all steps of tissue handling, and most laboratories have policies in place to keep such events to a minimum. Two areas in which cross-contamination may occur are the water bath and stainer. Platt and colleagues determined the frequency of tissue contaminants in a series of experiments performed in the histology laboratory at the Cleveland Clinic. Thirteen water baths used by individual histotechnologists were evaluated and contained only one tissue fragment. In contrast, analysis of slide stainers revealed a much higher rate of tissue contamination. The size of fragments in the strainers ranged from several cells to hundreds of cells. Contamination was most abundant in the initial series of xylene and alcohol baths. Furthermore, the tissue fragments in these baths adhered to 8% of blank slides run through the stainer. Presence of tissue fragments on blank slides was more prevalent in the late afternoon hours and virtually non-existent earlier in the day. Certain tissues were more prone to lifting and discohesion than others, including those that were friable (carcinoma), fragmented (endometrial curretings), or comprised of boney particles. The presence of contaminant tissue on slides examined by an anatomic pathologist can result in misdiagnosis. Although water baths did not seem to be problematic in this set of experiments, slide strainers represent a potential source of cross-contamination that must be accounted for in quality control policy and procedures.
Platt E, Sommer P, McDonald L, et al.:
The metrials glands of pregnant rats and mice are comprised of granulated metrial gland (GMG) cells, endometrial stromal cells, blood vessels, fibroblasts and trophoblasts. The glands are located in the mesometrial triangle of the wall of the uterus and are histologically visible from gestational day 8 until the end of pregnancy. GMG cells are natural killer cells derived from the bone marrow, and they are positive for perforin. The eosinophilic granules within the GMGs are PAS positive and diastase resistant. Importantly, GMG cells and their associated cell types (other than trophoblasts) can be observed in the nonpregnant uterus in pseudopregnancy, hormonal disturbances, and trauma. Therefore, conditions involving the metrial gland should be considered when evaluating lesions with granulated cells in the rat and mouse genital tracts. The purpose of this paper was to describe the normal histogenesis and immunohistochemical staining characteristics of normal metrial glands to aid in distinguishing conditions of the metrial gland from granular cell tumors. The gross and histological appearances of the metrial glands are described in detail throughout gestation. Immunohistochemistry showed GMGs to be positive for perforin. Decidualized endometrial stromal cells and trophoblasts were positive for neuron-specific enolase. The stromal cells were positive for S100, but GMGs and trophblasts were negative. The authors conclude that perforin staining and S100 can be used to help make a diagnosis of decidual reaction or reactive metrial gland. Both of these conditions should have positive cells (GMGs and stromal cells, respectively) which would not be expected in a neoplastic condition.
Picut CA, Swanson CL, Parker RF, et al.:
White-nose syndrome is a newly described, highly fatal entity observed in hibernating bats. It is associated with a Geomyces sp. of fungus that typically causes white lesions on the muzzle and wings. This paper describes the histological lesions needed to confirm the diagnosis of white-nose syndrome. Proper collection and processing of tissue from the muzzle and wing membrane are described. H&E staining demonstrates fungal hyphae invading the connective tissue underlying the skin and muzzle, but the fungi do not elicit a cellular inflammatory response. The hyphae are nonpigmented, branching and septate. They may have either parallel walls or irregular walls. The hyphae form cup-like erosions and ulcers in the epidermis of the wing and invade hair follicles and adnexa. Periodic acid-Schiff staining is necessary for complete identification of hyphae and conidia. The reason for a lack of immune response to the fungal infection is currently under investigation
Meteyer CU, Buckles EL, Blehert DS, et al.:
Understanding species-specific differences is essential in toxicology studies. Knowing which species metabolize certain compounds in a manner most like humans would help guide preclinical research and give investigators a better idea of the potential risks involved in using these compounds in humans. Rat hepatocyte model systems may not be ideal due to major differences between rat and human liver metabolism. In order to assess the suitability of porcine hepatocytes in metabolic studies, Langsch et al used organotypical cultures of primary human, rat, and porcine hepatocytes for a minimum of 14 days to study liver-specific functions and measure biotransformation of testosterone. Results of albumin measurements showed that the rat hepatocytes were twice as active as either the porcine or human hepatocytes. Similarly, the ethoxyresorufin-O-deethylase and ethoxycoumrain-O-deethylase assays also showed increased activity in rats. Testosterone biotransformation was similar in the porcine and human hepatocyte cultures but differed markedly in the rat, indicating that studies on testosterone biotransformation would be more informative if conducted using the porcine model. These experiments suggest that the metabolic activity of the porcine liver is a better model system than the rat liver for drug testing, and this knowledge may be useful in refining preclinical toxicology studies.
Langsch A, Giri S, Acikgoz A, et al.: