Low power: DQ Stain
Dual population of epithelial cells and lymphocytes
High power: DQ Stain
Epithelial cells in clusters in a background of lymphocytes
High power: DQ Stain
Epithelial cells in clusters with large nuclei and prominent nucleoli
Low power: Pap Stain
Epithelial cells in clusters in a background of lymphocytes
Low power: Pap Stain
Epithelial cells in clusters in a background of lymphocytes
High power: Pap Stain
B2 Thymoma
Epithelial cells in small clusters with large vesicular nuclei, prominent nucleoli, and moderate amounts of delicate cytoplasm
Medium power: Pap Stain
B2 Thymoma
Epithelial cells with large vesicular nuclei, prominent nucleoli, and moderate amounts of delicate cytoplasm in a background of lymphocytes
High power: Pap Stain
B2 Thymoma
Epithelial cells with large vesicular nuclei, prominent nucleoli, and moderate amounts of delicate cytoplasm in a background of lymphocytes
High power: Pap Stain
Epithelial cell clusters in a background of lymphocytes and lymphoid tangles
Cell block: H&E stain
Rare epithelial cell groups in a background of lymphocytes
Cell block
Immunoperoxidase stain for cytokeratin highlights epithelial cells
Low power: Pap Stain
Thymic carcinoma with features of squamous cell carcinoma
High power: Pap Stain
Thymic carcinoma with features of squamous cell carcinoma
Features
• Moderate to highly cellular smears
• Dual population (varying proportions)
– epithelial cells
– lymphocytes
• Hassall corpuscles rarely seen
• Epithelioid or spindled or clear cells
• Dense to clear cytoplasm
• Bland nuclei
• Nuclei may be large and vesicular (B2)
• Nuclei may show atypia (B3)
• Chromatin is fine and granular
• Inconspicuous to prominent nucleoli
• Lymphocytes with lymphoid tangles
• Type A: Predominantly spindled cells
• Type AB: Mixed with spindled and epithelial cells
• Type B1: Lymphocyte• rich
• Type B2: Epithelial cells and lymphocytes
• Type B3: Epithelial cell rich with atypia
• Thymic carcinoma (Type C)
• Epithelial cells express cytokeratin, p63, calretinin, mesothelin, CK5/6; negative for WT-1, TTF-1. Lymphoid cells express TDT, CD1a, CD99, while negative for CD20 and CD5 (positive in thymic carcinoma epithelial cells)
Tao LC et al. Acta Cytol. 1984 Mar-Apr;28(2):165-70.
Dahlgren S et al.Acta Cytol. 1983 Jan-Feb;27(1):1-6.