Inflammation / parasites
Trichomonas vaginalis

Author: John Philip, M.D. (see Authors page)
Editor: Ziyan T. Salih, M.D.

Revised: 28 August 2015, last major update August 2015

Copyright: (c) 2003-2015, PathologyOutlines.com, Inc.

PubMed Search: Trichomonas vaginalis [title] cervix
Cite this page: Trichomonas vaginalis. PathologyOutlines.com website. http://pathologyoutlines.com/topic/cervixcytologytrichomonasvaginalis.html. Accessed April 30th, 2017.
Definition / general
  • Trichomonas vaginalis is a parasitic protozoan that causes trichomoniasis, a sexually transmitted disease
  • Epidemiology
  • Trichomoniasis is the most prevalent nonviral sexually transmitted infection in the United States, affecting an estimated 3.7 million persons (CDC - Trichomoniasis)
  • Having multiple sexual partners is the primary risk factor
  • Mainly affects women from ages 16 - 35 years, but can occur in postmenopausal women
  • Sites
  • Female: vagina, cervix, urethra and occasionally Bartholin's gland
  • Male: urethra, epididymis and prostate
  • Clinical features
  • Most infected persons (70% - 85%) have minimal or no symptoms, and untreated infections might last for months to years (CDC - Trichomoniasis)
  • Copious yellow-green or gray-white vaginal discharge with a strong odor
  • Itching and irritation are frequent
  • Discomfort during sexual intercourse or urination
  • In pregnancy, can cause premature rupture of membranes and preterm delivery
  • Largely asymptomatic in men, act as a carrier; may cause urethritis
  • Diagnosis
  • Nucleic acid amplification test (NAAT)
  • OSOM trichomonas rapid test: Immunochromatographic test that detects pathogen antigens from vaginal swab
  • DNA hybridization probe test
  • Direct microscopic examination of secretions - wet mount
  • Culture: Was considered as a gold standard before the availability of molecular tests
  • Prognostic factors
  • Treatment reduces the signs and symptoms of infection and might reduce transmission (CDC - Trichomoniasis)
  • Case reports
  • 50 year old woman with "cannon balls or pus balls" in pap smears (J Clin Diagn Res 2013;7:1715)
  • Flagella-bearing bare Trichomonas vaginalis nuclei in Papanicolaou smears (Diagn Cytopathol 1988;4:87)
  • Treatment
  • Metronidazole or tinidazole
  • Sexual partners must also be treated
  • Clinical images
    Missing Image

    Strawberry cervix

    Microscopic (histologic) description
  • Pear-shaped, oval, or round cyanophilic organisms, 15 - 30 microns
  • Eosinophilic cytoplasmic granules are often evident
  • Nucleus is pale, vesicular, and eccentrically located
  • Flagella are sometimes observed
  • Leptothrix may be seen in association with Trichomonas vaginalis
  • Mature squamous cells with slightly enlarged, dark nuclei and small perinuclear halos ("trich change") are common that may mimic a low grade squamous dysplasia
  • 3 dimensional clusters of neutrophils (“polyballs”) may be seen in the background
  • Numerous lymphocytes and many mast cells may be seen
  • Organisms tend to be smaller and rounder with better visualized nuclei, cytoplasmic eosinophilic granules and flagella in liquid based preparations
  • Neutrophils and "polyballs" are reduced in liquid based preparations compared to the conventional smears
  • Occasional kite-shaped forms may be seen, especially on SurePath preparations (Nayar: The Bethesda System for Reporting Cervical Cytology, 3rd Edition, 2015)
  • Microscopic (histologic) images
    Missing Image Missing Image


    Missing Image

    Trichomonas in wet mount

    Missing Image Missing Image Missing Image

    Trichomonas in conventional pap smear

    Missing Image

    Trichomonas with leptothrix

    Missing Image

    Trichomonas vaginalis with leptothrix

    Missing Image

    Reactive squamous cells

    Missing Image


    Missing Image

    SurePath prep

    Missing Image


    Missing Image Missing Image

    Various images

    Missing Image

    Contributed by Dr. Marilin Rosa

    Electron microscopy images
    Missing Image Missing Image Missing Image

    T. vaginalis parasite

    Differential diagnosis
  • Cell fragments, cytoplasmic debris, bare epithelial nuclei, small mucus aggregates and leukocytes:
    • Identification of a definite elliptical nucleus helps avoid misinterpretation
    • Presence of eosinophilic cytoplasmic granules will be helpful
    • In most cases, trichomonad organisms are plentiful ("trich party")
      • Therefore, a rare fragment of cyanophilic debris is not likely to be a true trichomonad
  • Additional references