A pseudo‐outbreak of yeast in cell blocks associated with the use of human plasma

Abstract

Cell blocks are a useful adjunct to smears and monolayer slides in the evaluation of cytologic specimens. Their preparation captures residual small tissue fragments, clots, and cellular sediment, providing additional morphologic information in diagnostically challenging cases. 1,2 In addition, the use of cell blocks enables further immunostaining of paraffin embedded sections. Like other methods of slide preparation, however, this procedure is potentially prone to contamination by organic and inorganic material such as pollen, insects, and fungal organisms. 3 We describe a pseudo-outbreak of budding yeast forms found on cell block slides related to extrinsic contamination of the cell block process. Index CaseA 29-year-old man developed a Staphylococcal lugdunensis infection following arthroscopic surgery of his knee. He was treated with an arthroscopic ''washout'' and intravenous antibiotics. Despite this, pain and swelling in his knee progressed and he underwent joint aspiration on June 30, 2008, for re-evaluation. The synovial fluid appeared grossly turbid and was sent ''stat'' for cytologic exam. The patient was immediately taken to the operating room for arthrotomy, synovectomy, and debridement. Inflamed and necrotic-appearing tissue from the site was sent for culture and histopathology. Cytology of the synovial fluid was reviewed ahead and showed marked acute inflammation. In addition, budding yeast forms were noted in the cell block which lacked pseudohyphae, measured 2-5 microns in diameter, and were present in both H&E and Gomori methenamine silver (GMS) stained sections obtained from the same cell block (Fig. 1). Intraoperative specimens likewise showed acute inflammation but no organisms were seen and cultures were negative. Because of this unexpected finding, the clinician asked to review the cell block with the pathologist. Gram positive cocci in clusters consistent with Staphylococcus sp. were seen in addition to the yeast (Fig. 2). The ThinPrep TM , processed from the synovial fluid separately, was negative for yeast forms. Furthermore, cell blocks from other patient specimens processed on the same day were noted to have the same fungal organisms. This prompted an epidemiologic investigation to identify the source of cell block contamination. MethodsThe cell block preparation process was investigated and interviews with various personnel from the Cytology Laboratory were conducted.Cell blocks are prepared in our laboratory according to the plasma-thrombin method. 1,4 Fresh body fluid arrives at the Cytology Laboratory in a sealed container. A portion of the sample is placed in a labeled 50 ml centrifuge tube for cell block preparation. The tube is centrifuged (5 min at 2,500 rpm) and the supernatant decanted from the cell button. A nonsterile pipette is used to obtain three to four drops of outdated human plasma which is then added to the cell button and mixed. The plasma is not sterilized and is refrigerated in a glass container between uses.Three to four drops of thrombin, using another nonsterile...

Sodium Alginate versus Plasma Thrombin Cell Blocks in Diagnostic Cytopathology: A Comparative Analysis

“…Both plasma and thrombin are biological products and carry with them a small risk of being carriers of infectious agents or their products. Further, infectious agents especially fungi can grow in plasma as reported previously by Bravo et al [10]. Thrombin is also derived from rabbit or sheep brain and is subject to extensive testing and quality control.…”

Fungal contamination of Hanks solution

“…Bravo et al6 described a situation of contaminated cell blocks resulting in a pseudo‐outbreak of yeast in cytology specimens. Because of the disappearance of cases after the plasma was replaced with new stock, the most likely source of contamination was the expired human plasma.…”