Journal of Cytology
Home About us Ahead of print Instructions Submission Subscribe Advertise Contact e-Alerts Login 
Users Online:126
  Print this page  Email this page Small font sizeDefault font sizeIncrease font size

 Table of Contents    
Year : 2020  |  Volume : 37  |  Issue : 3  |  Page : 131-135
Contaminants and mimickers in cytopathology

Department of Pathology, Basaveshwara Medical College and Hospital, Chitradurga, Karnataka, India

Click here for correspondence address and email

Date of Submission11-Dec-2019
Date of Decision25-Jan-2020
Date of Acceptance13-Apr-2020
Date of Web Publication30-Jun-2020


Context: Many contaminants are routinely encountered in cytopathology practice. However, because of lack of familiarity and experience with them, many are unnoticed, neglected, or confused with other structures of major relevance. Aims: The purpose of this study was to intentionally introduce contaminants into the smears and to provide distinctive morphological criteria required for the microscopist to identify them confidently to avoid possible confusion. Settings and Design: Prospective cross-sectional study. Methods and Material: This study included smears prepared from the buccal mucosa of healthy volunteers. Common contaminants were deliberately introduced into the smears, fixed using 90% ethanol, and stained with Hematoxylin and Eosin stain (H and E) and Papanicolaou stain (PAP). The study also included smears from leftover cerebrospinal fluid (CSF) and wet mount preparations. The morphology of these contaminants was studied and the results were tabulated. Statistical Analysis Used: Nil. Results: The vivid morphological appearance of these commonly encountered contaminants were described and many of these mimicked structures of major relevance. Conclusions: Contaminants and mimickers can make the evaluation of cytologic specimens challenging and may necessitate secondary review by another pathologist or further workup. Knowledge and familiarity of these commonly encountered extraneous substances will help to prevent misinterpretation.

Keywords: Contaminants, cytopathology, mimickers

How to cite this article:
Muzarath S, Nandyal SS, Bindu B J, Murthy C N. Contaminants and mimickers in cytopathology. J Cytol 2020;37:131-5

How to cite this URL:
Muzarath S, Nandyal SS, Bindu B J, Murthy C N. Contaminants and mimickers in cytopathology. J Cytol [serial online] 2020 [cited 2021 Sep 20];37:131-5. Available from:

   Introduction Top

Contaminants are objects or phenomena influencing the appearance of smear and obstructing or even preventing proper analysis of important diagnostic factors of the cytological sample.[1] Contaminants and mimickers in cytologic smears have been considered as a potential diagnostic pitfall in cytodiagnosis.[1] Many contaminants are routinely encountered in cytopathology practice.[2] Several of them are considered as inherent and trivial but some, because of lack of familiarity and experience with them, are either unnoticed or neglected or confused with other structures of major relevance.[2] These contaminants cannot be completely eliminated but may only be minimized.[3] When these are encountered, their significance and ways to avoid them should be determined.[2] These have been meticulously projected at the tissue level but not so well at the cytological level except for some isolated thematic studies.[4]

   Aim and Objectives Top

The purpose of this study was to provide distinctive morphological criteria of contaminants required for the microscopists to identify them confidently to avoid possible confusion.

   Methodology Top

It was a prospective cross-sectional study. Study included smears prepared from the buccal mucosa of healthy volunteers. Common contaminants were deliberately introduced into these smears which were fixed with 95% ethyl alcohol and stained with haematoxylin and eosin stain and Papanicolaou stain. The study also included smears from leftover cerebrospinal fluid (CSF). Wet mount preparations using tap water were used to study glove powder, pollen grains, and plant origin contaminants. Cytological artifacts pertaining to fixation, drying, and smearing were excluded from the study.

A single blind study was conducted in which the smears were viewed by two cytologists for identification and morphological description of the contaminant using light microscope Labomed L × 400 and later these were subjected to polarizing microscopy. Their effect on interpretation of smears was noted. Buccal smear sampling from the volunteers included an informed consent along with preserving the anonymity. Ethical clearance was obtained from institutional ethical committee.

Many of the contaminants presented in this paper are considered as either intrinsic (sample contaminants derived from patient) or extrinsic contaminants (contaminants of cytological smears incorporated during their processing). Common contaminants introduced included:

First category

(Iatrogenic contaminants)- Procedure-related contaminants like lubricants, ultrasonography gel (USG gel), fibers (natural/synthetic), glove powder, and blood.

Second category

-Extraneous substances that may get introduced during slide preparation and processing like air bubbles, dust particles, exfoliated squamous cells, plant matter (pollens, trichome, etc.), bacterial and fungal growths, airborne (spores) and waterborne contaminants (algae), stain precipitates, human hair, etc.

Third category

-Contaminants derived from the patient like normal flora, fibrin strands, skeletal muscle fragments, RBCs, food contaminants, etc.

   Results Top

The vivid morphological appearance of these commonly encountered contaminants was studied and described. Many of these mimicked structures of major relevance. The morphological appearances of contaminants with their possible mimickers are listed in [Table 1] and [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5].
Table 1: Morphological appearances and possible mimics of commonly encountered contaminants

Click here to view
Figure 1:(a)-Albumenized slide, PAP × 10. (b)- Desquamated squamous cells in CSF, PAP × 10. (c)-Dust particles, PAP × 10. (d)- Stain precipitate, H and E × 10. (e)-Hair, PAP × 4. (f)- Lubricant gel, (xylocaine) H and E × 10. (g)-medication gel (candid V), PAP × 40. (h)-USG gel, PAP × 10

Click here to view
Figure 2: (a, b)- Cotton fiber, PAP × 10, Polarized microscopy × 40.(c, d)-Gauze fiber, PAP × 40, Polarizer × 40. (e, f)-synthetic fiber (tampon fiber), PAP × 40, Polarizer × 40. (g-i)-Glove powder, PAP × 4, wet mount × 40, Polarizer × 40

Click here to view
Figure 3: (a, b)-Pollen of parthenium, large round to oval in shape with speculated exine, H and E × 40, wet mount × 40. (c, d)- Plant trichome, PAP × 4, wetmount × 40. (e-h)-Grass pollen wet mount × 40

Click here to view
Figure 4: Algae: (a-c, e, f, h)- Round and pennate diatoms (Silicated cell wall), PAP × 40. (d)-Blue filamentous algae PAP × 40. (g)-Green Ulothrix, unbranched filamentous algae with single row of identical cells and thick cell walls

Click here to view
Figure 5: Food particles(a)-Green chilli, H and E × 10. (b)-Garlic, PAP × 10. (c)-Ginger, H and E × 10. (d)-Onion, PAP × 10. (e)-skeletal muscle fiber, PAP × 40. (f)-Carrot- H and E × 10.(g)- Coriander, H and E × 10

Click here to view

Some of the contaminants like glove powder, plant cell wall, dust particles, insect parts, cotton fibers, and synthetic fibers showed positive birefringence under polarized microscopy. Glove powder showed Maltese cross birefringence [Figure 2]. Pollen, algae, vegetable cells, USG gel, lubricants, and fungus were negatively birefringent. Air and trichomes showed partial birefringence.

Pollen grains and plant trichomes chosen for the study belonged to various species of commonly seen flowering plants around our laboratory, particularly parthenium, grass pollen, and Chloris barbata [Figure 3].

Commonly encountered airborne fungal spores, which included Aspergillus, Penicillium, and Alternaria, were introduced into the smears from culture tubes and bread molds. Either entire conidiophores or isolated conidia were found on smears. Spores of Aspergillus and Penicillium were of same size and shape. Alternaria appeared as racket-shaped macroconidia with longitudinal and transversal support. Algae samples commonly grown on the surface of stagnant water were chosen to study their varied morphology as depicted in [Figure 4].

Various cooked vegetable particles were introduced on to the smears as contaminants. Vegetable cells appeared in clusters and in singles. Individual cells of green chilli were polygonal with large hyperchromatic nucleus resembling malignant cells. Garlic cell clusters were of polygonal/ballooned cells with central small round nuclei, resembling squamous cells. Ginger cell, clusters of round cells, mimicked a fatty tissue fragment. Onion cells appeared as compactly arranged sheets of polygonal cells with small dark nucleus. Meat skeletal muscle fibers showed prominent striations [Figure 5].

   Discussion Top

A great variety of exotic contaminants may pollute the cytology smears. These may be intrinsic (from patient) or extrinsic which generally arise from surgeon's chair or pathologist's laboratory.[4] Few contaminants can be trivial but some of them can result in false diagnosis or misclassification of the lesion.[1] Polarization is a useful procedure to help recognize these foreign bodies since many are birefringent.[5] Many of the potential common and uncommon contaminants that are encountered in cytology practice are discussed hereunder.

Hasty cover slipping or areas of thick unevenly distributed cytological material result in air bubbles and mounting of wet slide gives rise to water bubbles.[3] Air trapping under coverslip is referred to as cornflakes or brown cell artefact.[6] Stain precipitates form as staining solutions age. Precipitates can also form if a saturated solution of stain is allowed to evaporate or dry up on the smear.[1]

Lubricating gel contamination compromises the adequacy and causes serious interpretation errors in both conventional and liquid based preparations of cervical smears.[7],[8] Lubricant contamination can also occur in endoscopy and cystoscopy guided specimens.[3] Albumenized slides and lubricant gels morphologically simulate mucin but lack of columnar cells, inflammation, and debris can be a differentiating feature. Ultrasound gel results from guided aspirations and from stain build up.[3]

Desquamated Squamous epithelial cells usually represent contaminants from patient's oral cavity or upper respiratory tract in respiratory cytology. Exfoliated cells from hands and from sneeze droplets can also act as source.[3]

Glove powder typically used to facilitate donning in surgical gloves is modified corn starch. It is a well-recognized potentially confusing common contaminant of cytological specimens.[6],[9]

Normal bacterial flora and candida elements are common contaminants in vaginal, oropharyngeal, and urine samples.[2] Unsterile instruments, unsterile stains, time delay to reach laboratory, and poor sample preservation lead to overgrowth of microbes.[2] Contamination of smears by bacterial and fungal spores can mimic true infection. Positive clinical findings and the presence of significant inflammation in the smears aid in differentiating contamination from true infection.[10],[11] Some intrinsic endogenous structures which act as pseudo microbes include RBCs, platelets, mucus, tissue fibers (skeletal, elastic), fibrin ciliocytophthoria, Liesegang rings, and psammoma bodies.[2],[12]

A variety of pollen grains and airborne fungal spores (especially Alternaria, Aspergillus, Penicillium, Fusarium) are ubiquitous in the atmosphere and hence gain entry onto glass slide from contamination of collection materials or laboratory equipments.[2],[13] Fungal spores may also be inhaled and then deposited in various parts of respiratory tract and act as intrinsic contaminants.[14] Air spores are well studied as allergens and their concentration varies according to seasonal periodicity.[15],[16]

Pollen grains are round or ovoid in shape, 6–100 μm with a double wall, inner wall being thin and delicate. Outer wall is smooth or rough with warts, grains, troughs, etc.[2] In a study by Accorsi et al., smears with pollen content higher than 15 grains per slide were recorded in pollinosis patients. In case of intrinsic contamination, stained pollen grains are at the same depth of focus as the cytological material.[17] Pollens and plant cells in stool may be confused for a variety of helminth eggs especially of taenia species and Trichuris trichiura eggs. Features like small size, lack of hooked oncospheres, and embryo wall help in distinguishing these from parasite ova.[18]

Human tissue fibers (skeletal muscle or elastic fibers), suture material, strands of mucus (Curschmann's spirals), and plant matter (plant hairs) mimic parasite worms. Their existence in unusual shapes like sharp kinks, lack of external (mouth, hooks, etc.) and internal (digestive or reproductive tract) noticeable anatomical structures are often vital in differentiating contaminants from real worms.[2],[5]

The sources of fiber contaminants include cotton swabs, gauze, hair, cytobrush bristles, commercial tampons, etc.[19] In the study by Van Hoeven and Bertolini, fibers were identified in 178 of 1368 cervical smears with cotton and rayon being the most common ones.[19] The surface of natural fibers like cotton shows a series of lines forming a fringe along the whole of its length, whereas the surface of synthetic fibers shows dotted pattern.[1],[2] Features such as geometric shape, absence of nuclei, and lack of septation assist in differentiating these contaminants from real findings.[3]

Presence of microalgae in cytology smears can be from intrinsic contamination or from tap water.[17] They may be unicellular or multicellular, assume different morphologies.[2],[20] Diatoms range from 2–200 μm, either circular, elliptical or triangular in shape contained within silicated cell wall.[2] Their presence indicates faulty water purification system.[20] Algae in body fluids and viscera may be used in the investigation of death by drowning.[20] Algae have been confused with fibers of vegetable origin, synthetic fibers, and pollen.[20]

Food contaminants can originate from brushings of the GIT, anal  Pap smear More Detailss, urinary diversion specimens, or as an aspirated contaminant in respiratory specimens.[2],[21],[22] In respiratory cytology specimens, vegetable contaminants may be mistaken for squamous cell carcinoma. Identification of refractile cell wall is the key to avoid this pitfall.[23]

Martinez-Giron et al. noticed both freshwater and terrestrial arthropods in routine Papanicolaou smears and considered them as due to accidental contamination of samples.[24]

Some of the important factors that differentiate contaminants from genuine findings include their presence on any one of the slide, location of structure at the edge of slide, and its placement in a different focal plane.[2] Contaminants can be minimized by following simple measures like proper patient preparation before sample collection, strict adherence to standard operating protocol in terms of sample collection, preservation, and processing, proper preparation and maintenance of stains and fixatives, maintaining clean working area and with good clinical correlation. Ours is a unique study because it is a first comprehensive catalogue illustrating and describing the cytological contaminants to bring awareness among pathologists.

It was a modest attempt at providing morphological appearances of a variety of familiar and unfamiliar contaminants acting as potential mimickers. They may pose difficulty to the unwary and may cause a potential “wild goose chase” that can result in wasted valuable time and resources. Our basic concept was to bring awareness among Pathologists because “what the mind does not know eyes cannot see.”


We are thankful to the volunteers who participated in our study.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the participants have given their consent for their images and other clinical information to be reported in the journal. The participants understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

Chukwuemeka KI. Artefacts in cytology [Internet]. http://www.academia.adu. Available from: [Cited 2019 Jun 10].  Back to cited text no. 1
Pantanowitz L, Goulart RA, Martinez-Giron R. Mimics and contaminants. In: Ali Syed Z, Clark DP, Erozan SY, editors. Cytopathology of Infectious diseases. 2012 ed. NewYork: Springer; 2011. p. 351-77.  Back to cited text no. 2
Kahwash SB. Artifacts, contaminants and mimics in cytology. In: Monaco S, Teot L, editor. Pediatric Cytopathology. 1st ed. Berlin, Heidelberg: Springer; 2017. p. 231-44.  Back to cited text no. 3
Sahay K, Mehendiratta M, Rehani S, Kumra M, Sharma R, Kardam P. Cytological artefacts masaquerading interpretation. J Cytol 2013;30:241-6.  Back to cited text no. 4
[PUBMED]  [Full text]  
Martinez –Giron R, Gonzalez-Lopez JR, Esteban JG, Garcia-Miralles MT, Alvarez-de-los-Heros C, Ribas-Barcelo A. Worm-like artefacts in exfoliative cytology. Diagn Cytopathol 2006;34:636-9.  Back to cited text no. 5
Hoda RS, Hoda SA. Artifacts, contaminants and incidental findings. In: Fundamentals of Pap Test Cytology. 2007 ed. Totowa, New Jersy: Humana Press; 2007. p. 179-86.  Back to cited text no. 6
Charoenkwan K, Ninunanahaeminda K, Khunamornpong S, Srisomboon J, Thorner PS. Effects of gel lubricant on cervical cytology. Acta Cytol 2008;52:654-8.  Back to cited text no. 7
Gaffar AB, Kamal MO, Khalid M, Samuel R, AlGhufli R. Lubricant, mucus and other contaminant materials as a potential source of interpretation errors in Thinprep cervical cytology. J Low Genit Tract Dis 2010;14:22-8.  Back to cited text no. 8
Jadhav KB, Gupta N, Ahmed Mujib BR. Maltese cross: Starch artefact in oral cytology, divulged through polarized microscopy. J Cytol 2010;27:40-1.  Back to cited text no. 9
[PUBMED]  [Full text]  
Kini H, kini JR, Suman E, Rai S. Fungal spores and fruiting bodies in cervicovaginal smears: Contaminant or infection. Diagn. Cytopathol 2017;45:191-4.  Back to cited text no. 10
Sharma P, Kumar N, Jain S. Fungal contaminants in cytopathology specimens. Biomed J 2014;37:31-2.  Back to cited text no. 11
[PUBMED]  [Full text]  
Saeeda A, Sameer BK. Detached respiratory cilia: An organism mimicker in BAL specimens. Adv Anat Pathol 2011;18:414.  Back to cited text no. 12
Martinez –Giron R, Gonzalez-Lopez JR. Uncommon fungal contamination in urine cytology. Diagn Cytopathol 2012;40:234-5.  Back to cited text no. 13
Martinez –Giron R, Ribas-Barcelo A, Garcia-Miralles MT, Lopez-Cabanilles D, Tamargo-Pelaez ML, Torre-Bayon C, et al. Airborne fungal spores, pollen grains and vegetable cells in routine papanicolaou smears. Diagn Cytopathol 2004:30:381-5.  Back to cited text no. 14
Singh AB, Kumar P. Aerial pollen diversity in India and their clinical significance in allergic diseases. Indian J Clin Biochem 2004;19:190-201.  Back to cited text no. 15
Ahmed S. Air borne fungal spores- A review. Pak J Phytopathol 2007;19:179-91.  Back to cited text no. 16
Accorsi CA, Mazzanti MB, Forlani L, Rivasi F. Pollen grains in human cytology. Grana 1991;30:102-8.  Back to cited text no. 17
Colmer- Hamood JA. Artefacts mimicking ova and parasites. Lab Med 2001;32:80-4.  Back to cited text no. 18
Van Hoeven KH, Bertolini PK. Prevalence, identification and significance of fibre contaminants in cervical smears. Acta Cytologica 1996;40:489-95.  Back to cited text no. 19
Martinez-Giron R, Ribas-Barcelo A. Algae in cytologic smears. Acta Cytol 2001;45:936-40.  Back to cited text no. 20
Chang S, Moatamed NA, Christina KY, Salami N, Apple SK. The sheep in wolf's clothing: Vegetable and fruit particles mimicking cells and microorganisms in cytology specimens. J Cytol Histol 2013;5:1-11.  Back to cited text no. 21
Garza GQ, Nassar D, Khalbuss WE, Monaco SE, Pantanowitz L. Vegetable cell contaminants in urinary bladder diversion cytology specimens. Acta Cytol 2012;56:271-6.  Back to cited text no. 22
Idowu MO, Powers CN. Lung cancer cytology: Potential pitfalls and mimics- a review. Int J Clin Exp Pathol 2010;3:367-85.  Back to cited text no. 23
Martinez-Giron R, Gonzalez-Lopez JR, Escobar-Skin J, Jou-Munoz C, Garcia-Miralles MT, Ribas-Barcelo A. Freshwater microorganisms and other arthropods in Papanicolaou smears. Diagn Cytopathol 2005;32:222-5.  Back to cited text no. 24

Correspondence Address:
Dr. Sonam S Nandyal
Department of Pathology, Basaveshwara Medical College and Hospital, Chitradurga - 577 501, Karnataka
Login to access the Email id

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/JOC.JOC_159_19

Rights and Permissions


  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]

  [Table 1]


    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
    Email Alert *
    Add to My List *
* Registration required (free)  

   Aim and Objectives
    Article Figures
    Article Tables

 Article Access Statistics
    PDF Downloaded341    
    Comments [Add]    

Recommend this journal