• SALIVARY GLAND
• HISTOPATHOLOGY
• IMMUNOHISTOCHEMISTRY

The histogenesis of Warthin tumours (WT), whether true neoplasm or hyperplasia, is still a matter of debate.1–4 We had recently the opportunity to study the expression of the HBME1 antigen in parotid WT. The HBME1 antibody, raised to cultured mesothelioma cells, is now used routinely in the differential diagnosis of malignant tumours, mainly between mesothelioma and adenocarcinoma as well as in the diagnosis of malignancy of thyroid nodules.5 ,6 Interestingly, there are data also on HBME1 expression in normal tissues other than the mesothelium, including in salivary glands.7

The immunohistochemical expression of HBME1 as well as of CK5/6, P63, WT1 and Bcl2 was evaluated in the epithelial component of four WTs. The amounts of epithelial and lymphoid components were relatively equal in all the studied tumours. Expression of HBME1 in a membrane and cytoplasmic pattern was detected with a heterogeneous distribution, in luminal, suprabasal and basal epithelial cells (figure 1). Cytokeratin (CK) 5/6 and P63 stainings were also similar in the cases we have tested. CK5/6 as well as P63 was expressed in a focal pattern, in basal cells and suprabasal cells. Rare cylindrical cells expressed CK5/6. WT1 was expressed focally at the luminal border of tumour epithelium (without nuclear positivity) …