Pap stain, high power
Decoy cell
Pap stain, high power
Two cells - upper with developing inclusion and granular chromatin and lower with fully developed inclusion.
Note the cells with inclusions can show nuclear size variation
Pap smear, high power
Examples of Type-1 and Type-3 inclusions. Note the ground glass inclusions that push the chromatin and give the appearance of thickened membranes
Pap smear, medium power
CMV-like inclusion
Pap smear, high power
Comet like cell with eccentric nucleus, thickened nuclear membrane and hyperchromasia. All these features are seen in urothelial carcinoma; however, in this example very rare cells of Polyoma virus infection were seen and all of them had regular nuclear contours
Pap stain, high power
Herpes like inclusions of Polyoma are very rarely seen. These happen when the virus infect the urothelial cells, particularly the umbrella cells
Pap stain, high power
Three cells with intranuclear basophilic inclusions. Although cellular hyperchromasia may be concerning the nuclear contour is perfectly round and coarsely granular chromatin of cancer cells is NOT seen
Pap stain, medium power
CMV like inclusion with a halo. These inclusions are uncommon and are believed to be a phase in the development of usually seen Type-1 inclusions where the viral particles replace the entire nucleus
Pap stain, high power
Five cells with classic polyoma virus inclusions characterized by glassy appearance and thickening of nuclear membranes.
Note the high N:C ratios, but rounded nuclear contours
Pap stain, high power
An example showing both Type-1 and Type-2 inclusions in a single cell
Features
• Renal tubular cells
• Urothelial cells
• Predominantly single cells
• Cells may be numerous in immunocompromised patients
• Enlarged nucleus with high nucleus to cytoplasmic ratio
• Rounded nuclear contour
• Hyperchromasia
• Thickened nuclear membrane
• Intranuclear inclusions:
– Type• 1 inclusion • Basophilic, ground glass or opaque inclusion
– Type• 2 inclusion • CMV like basophilic to amphophilic with a surrounding halo
– Type• 3 inclusion • Herpes like glassy inclusion with multinucleation and nuclear molding
• Usually clean background with no necrosis
• The nuclear features of the polyoma virus infected cells can lead to misdiagnosis as cancer, hence the cells are called Decoy cells. However, unlike the high grade urothelial carcinoma, Decoy cells have rounded nuclei
Singh HK et al. Adv Exp Med Biol. 2006;577:201-12.
Herawi M et al. Am J Surg Pathol. 2006 Mar;30(3):345-50.