Journal of Cytology
Home About us Ahead of print Instructions Submission Subscribe Advertise Contact e-Alerts Login 
Users Online:752
  Print this page  Email this page Small font sizeDefault font sizeIncrease font size

 Table of Contents    
Year : 2019  |  Volume : 36  |  Issue : 4  |  Page : 209-210
False paragonimus eggs in sputum cytology

1 INCLÍNICA Foundation, Oviedo, Spain
2 Faculty of Pharmacy, University of Salamanca, Spain

Click here for correspondence address and email

Date of Submission25-Feb-2019
Date of Decision08-Jun-2019
Date of Acceptance07-Aug-2019
Date of Web Publication20-Sep-2019

How to cite this article:
Martinez-Giron R, Martinez-Torre C. False paragonimus eggs in sputum cytology. J Cytol 2019;36:209-10

How to cite this URL:
Martinez-Giron R, Martinez-Torre C. False paragonimus eggs in sputum cytology. J Cytol [serial online] 2019 [cited 2021 May 11];36:209-10. Available from:

Due to passage through the oral cavity, a sputum sample may be contaminated by saliva or other elements, such as food particles. The presence of different types of contaminants in sputum smears, including pollen grains, fern spores, diatoms and others, which mimic parasitic eggs, has been occasionally documented in the medical literature.[1]

A 52-year-old male, heavy smoker (two packs a day) arrived at the emergency room with chest pain, a productive cough, and intermittent episodes of haemoptysis over the last 3 months. His body temperature was normal and wheezing was evident on auscultation. The rest of the clinical exam was unremarkable. Chest x-ray, sputum cytology, blood test, and mycobacterial culture were initially carried out. During the course of the exam, the patient reported traveling to Southeast Asia 1 year prior.

The chest x-ray led to the initial diagnosis of bronchiectasis, which was later supported by a thoracic CT, showing numerous dilated and thick-walled airways filled with mucus in many zones of both lungs.

The sputum smear, stained using the Papanicolaou method, showed the presence of two wide structures [Figure 1]a, that were ovoid in shape and measured approximately 85 × 50 μm, with a greenish/bluish hue. One of the ends was rounded but the other seemed flattened (black arrow), similar to an opening (operculum-like). Both structures were delineated by a thin, transparent capsule. Some striations were observed under the surface.
Figure 1: (a) Sputum cytology. Starch granules (Papanicolaou stain, ×400). (b): Starch granules under polarized light. (c) Sputum cytology. P. westermani egg (Papanicolaou stain, ×400). (d) P. westermani egg under polarized light

Click here to view

In addition, some areas of the sputum smear showed squamous metaplasia and many Globet cells. No atypical/malignant cells were observed.

Among the different diagnostic possibilities, the presence of contaminants was taken into account, but because of the patient's clinical records, a Paragonimus pulmonary infection with the presence of worm eggs in the sputum smear was not ruled out. Nevertheless, examination of these structures under polarized light, showed a typical Maltese cross appearance [Figure 1]b, which is characteristic of starch granules, such as those in the talc grains from medical glove powder.[2]

On the other hand, the results of the blood test were within normal ranges, including the eosinophil count, and the mycobacteria culture was negative.

In view of these findings, the final diagnosis was bronchiectasis in a heavy smoker patient, and a pulmonary parasitic infection due to the trematode Paragonimus westermani was ruled out.

Nevertheless, it is necessary to highlight key morphological features in order to differentiate between true P. westermani eggs and starch granules.

The eggs of P. westermani are golden brown, oval in shape with a flat operculum at one end (black arrow), approximately 45-70 × 80-120 μm in size, and have a thick birefringent shell [Figure 1]c. Under polarized light the shell is only noticed [Figure 1]d.

Starch granules observed in sputum smears, and stained by the Papanicolaou method, are ovoid in shape, vary greatly in size, and have a thin cell wall. They may appear as translucent/refractive structures or with different colours. Under polarized light, a Maltese cross appearance is very characteristic.

Pulmonary paragonimiasis is a food-borne zoonotic disease caused by a trematode of the genus Paragonimus. About 48 species of Paragonimus have been described. Nevertheless, only 16 of these can infect humans, P. westermani being the most common. They can cause pulmonary and pleural inflammation following the ingestion of raw freshwater crabs or crayfish infected with metacercariae, the infective stage of the worm.[3] This infection is commonly observed in Asia, in several countries such as China, Japan, Korea, Taiwan, the Philippines, Indonesia, and India. It has been also reported in South America and Africa.

Although this lung infection is rare in developed countries, some cases have been reported after the consumption of raw crayfish from rivers.[4]

The principal manifestations of pulmonary paragonimiasis are persistent cough, fever, and haemoptysis. This infection may also be misinterpreted as lung cancer or pulmonary tuberculosis.[5],[6]

In the life cycle of this trematode, the eggs are not yet mature when laid, therefore no embryonic structures are observable inside. Unembryonated eggs may be expelled with the sputum or may be swallowed and eliminated through the faeces.

Therefore, we think that this finding should be taken into account during microscopic observation, as a correct diagnosis is important. It will prevent the patient from going through more aggressive procedures, such as a biopsy, unnecessary therapeutics, and complicated diagnostic analysis.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients 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

Pantanowitz L, Goulart RA, Martínez-Girón R. Mimics and Contaminants. In: Rosenthal DL, editor. Cytopahology of Infectious Diseases. New York: Springer; 2011. p. 351-77.  Back to cited text no. 1
Jadhav KB, Gupta N, Ahmed MB. Maltese cross: Starch artefact in oral cytology, divulged through polarized microscopy. J Cytol 2010;27:40-1.  Back to cited text no. 2
[PUBMED]  [Full text]  
Doanh PN, Horii Y, Nawa Y. Paragonimus and paragonimiasis in Vietnam: An update. Korean J Parasitol 2013;51:621-7.  Back to cited text no. 3
Lane MA, Barsanti MC, Santos CA, Yeung M, Lubner SJ, Weil GJ. Human paragonimiasis in North America following ingestion of raw crayfish. Clin Infect Dis 2009;49:55-61.  Back to cited text no. 4
Song JU, Um SW, Koh WJ, Suh GY, Chung MP, Kim H, et al. Pulmonary paragonimiasis mimicking lung cancer in a tertiary referral centre in Korea. Int J Tuberc Lung Dis 2011;15:674-9.  Back to cited text no. 5
Ratsavong K, Quet F, Nzabintwali F, Diendéré J, Sebert J, Strobel M, et al. Usefulness and limits of Ziehl-Neelsen staining to detect paragonimiasis in highly endemic tuberculosis areas. Parasite Epidemiol Control2016;2:1-7.  Back to cited text no. 6

Correspondence Address:
Dr. Rafael Martinez-Giron
Inclinica Foundation, Oviedo
Login to access the Email id

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/JOC.JOC_33_19

Rights and Permissions


  [Figure 1]


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

    Article Figures

 Article Access Statistics
    PDF Downloaded79    
    Comments [Add]    

Recommend this journal