Microscopic description and IHC:

Papillary and cystic lesion composed of epithelial and lymphoid components.

The papillary projections are lined by a double layer of granular eosinophilic cells (oncocytic epithelia).
  • Inner (luminal) cells: nonciliated, tall columnar cells with nuclei aligned toward lumen.
  • Outer (basal) cells: round, cuboidal cells with vesicular nuclei.
  • Prominent oncocytic appearance of cells is due to presence of increased mitochondrial content.

Lymphoid component of mature lymphocytes with lymphoid follicles and germinal centers.

Immunohistochemical features:
  • Epithelial cells (luminal):
    • CK7, CK8, CK18 and EMA positive
    • S100, p63, calponin, GFAP and actin negative
  • Lymphoid cells:
    • CD20, CD3, CD4, CD8 and CD56 positive

These IHC stains are not used in practice for the diagnosis.

Discussion:

Warthin tumor or Papillary cystadenoma lymphomatosum is a benign salivary gland tumor characterized by cystic and papillary growth, presence of bilayered epithelial proliferation and presence of associated mature lymphocytic cell stroma.

There is a strong link between Warthin tumor and cigarette smoking.

It is the 2nd most common benign salivary gland tumor (following pleomorphic adenoma).

This tumor almost exclusively involves parotid gland, particularly the superficial lobe adjacent to the mandibular angle.

References:

Thompson, L. D. R., MD (2013). Head and Neck Pathology (2nd ed., Foundations in Diagnostic Pathology). Philadelphia, PA: Elsevier Saunders.

Thompson, L. D., MD, & Wenig, B. M., MD. (2012). Diagnostic Pathology Head and Neck (1st ed.). Altona, Canada: Amirsys.

CASE IMAGES