Md. Gibbons et al., Molecular differences in mucoepidermoid carcinoma and adenoid cystic carcinoma of the major salivary glands, LARYNGOSCOP, 111(8), 2001, pp. 1373-1378
Objective/Hypothesis. Mucoepidermoid carcinoma (MEC) and adenoid cystic car
cinoma (ACC), the most common malignancies of the major salivary glands, ar
e clinically and pathologically different. To determine whether MEC and ACC
have different molecular characteristics, we examined the expression of er
bB-2, erbB-3, epidermal growth factor receptor (EGFR), and transforming gro
wth factor-alpha (TGF-alpha), important molecular features in other maligna
ncies. Study Design/Methods. Archival tissue sections of 22 MEC and 6 ACC t
umors of the major salivary glands were evaluated immunohistochemically for
expression of erbB-2, erbB-3, EGRF, and TGF-alpha. A differential immunost
aining score, reflecting the difference in immunostaining between carcinoma
and uninvolved salivary gland tissue, was calculated for cytoplasmic and m
embranous staining. Results. Positive immunostaining for all biomarkers was
observed in the cytoplasm and membrane of both tumors. However, expression
was higher in MEC than in ACC tumors and was statistically significant for
cytoplasmic EGFR (P =.009), TGF-alpha (P =.041), and membranous EGFR (P =.
004). A significantly higher percentage of MEC cells also demonstrated posi
tive immunostaining for cytoplasmic erbB-3 (P =.022), EGFR (P =.005), membr
anous erbB-3 (P =.022), and EGFR (P =.013). The differential immunostaining
score was significantly higher for MEC compared with uninvolved alveolar t
issue and the membranes of uninvolved ductal tissue. There were no statisti
cally positive differential immunostaining scores for ACC. Conclusions. The
re is a clear difference in the molecular phenotypes of MEC and ACC. The la
ck of statistically significant expression in ACC, when compared with simil
ar uninvolved. salivary gland tissue, suggests minimal involvement for thes
e molecular structures in the pathogenesis of ACC. Conversely, erbB-2, erbB
-3, EGFR, and TGF-alpha may have a role in the development and progression
of MEC. These results have therapeutic implications for MEC of the major sa
livary glands.