An antibody which reacts with a mesothelial cell membrane antigen located in microvilli. Whilst HBME1 has a low specificity in differentiating mesotheliomas from adenocarcinomas, it is often positive in papillary carcinoma of the thyroid.
Among less commonly used antibodies, reactivity to mesothelin was found in 28 of 30 cases (93%); HBME1, 28 of 30 (93%); WT1, 22 of 27 (81%); D2-40, 20 of 22 (91%); and cytokeratin 5, 18 of 18 (100%).
Malignant mesothelioma cells also express podoplanin (D2-40) (e), HBME1 (f), and mesothelin (g) as markers of the mesothelial lineage, whereas there is no reactivity to carcinoembryonic antigen (CEA) (h), thyroid transcription factor 1 (TTF-1, absent brown nuclear staining) (i), or Napsin A (red) (i).
Cytokeratin 19 expression was cytoplasmic, CITED1 expression was nuclear and cytoplasmic, and HBME1 expression was membranous, apical, and cytoplasmic (Figure 2, A through D).
High-Density TMA.--Only 4 follicular adenomas (of 26) and 1 goiter (of 27) were positive for HBME1 on the TMA (5 of 80), whereas the corresponding whole section immunohistochemistry showed positive expression in 9 cases (1 of 8 FTCs, 4 of 26 adenomas, and 4 of 27 goiters).
The cumulative core loss for CK 19, HBME1, and CITED1 was 10% in HD-TMA and 13% in LD-TMA.