Case of the Month: Cytopathology

April 2017 Case of the Month authored by Cytopathology Unit Director Marino Leon, M.D., FCAP, FASCP


A 65-year-old male presented with right pleural effusion; focal pleural thickening was identified by computerized tomography (CT) scan. A pleural fluid aspiration was submitted to the University of Florida Health Pathology Laboratories Cytopathology Laboratory.

Immunohistochemical studies

Figure 1: Cluster of cells with irregular edge (Papanicolaou stain)


Figure 2: Group of cells with tridimensional architecture; the cells show high nuclear-to-cytoplasmic ratios and cells with irregular nuclear outlines (Papanicolaou stain).


Figure 3: Spherical cluster of cells with irregular nuclear outlines and nuclear grooves (hematoxylin and eosin; cell block)


Figure 4: The tumor cells are positive for MOC-31 immunostain.


Figure 5: The tumor cells are positive for TTF-1 immunostain.



(Hover the cursor over the link above to read the diagnosis for this case.)



Key cytopathologic features:

  • Groups of cells in the fluid, usually showing a smooth edge (i.e., community border)
  • Cells with sharp cytoplasmic edges
    • Lack of double edges or fuzzy cytoplasmic edges
    • Lack of intercellular spaces (i.e., windows)
  • Cytoplasmic vacuoles and signet ring cells
  • Immunohistochemical stains
    • MOC-31, berEP4, and monoclonal CEA positive
    • Expression of thyroid transcription factor-1 (TTF-1) and napsin-A
    • The cells may express cytokeratin 5/6 and p63, focally.
    • These cells are negative for calretinin, D2-40 and WT-1.
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