Reference ID: SP-T-12A
History: A 35 y/o female presented with a history of itching and foul smelling yellow-green discharge.

Diagnosis: Trichomonas Vaginalis
Discussion:
Trichomonas is an oval or pear-shaped organism with an elliptical nucleus, red cytoplasmic granules, and flagella. The diagnostic rule of thumb is: you must see the nucleus for diagnosis, you may see the red granules in the cytoplasm, but you will never see the flagellum in pap smears.
Pap smear features accociated with Trichomonas are cannonballs, pseudokeratinization in the cytoplasm, slightly enlarged and dark nuclei and perinuclear halos.
Dirty, granular background is common and may resemble diathesis.
In the liquid-based preparations, organisms tend to be smaller due to rounding; occational kite-shaped forms may be seen; nuclei and eosinophilic granules are often better visualized; and flagella may be preserved and identified.

Reference:
Demay 2nd Edition: pages 40, 41, 162.
Bethesda page 23 to 25.