C-kit expression distinguishes salivary gland adenoid cystic carcinoma from polymorphous low-grade adenocarcinoma.
Adenoid cystic carcinoma (ACC) is characterized by persistent, relentless growth and a high rate of eventual metastasis. In contrast, polymorphous low-grade adenocarcinoma (PLGA) has a much lower risk of recurrence and rarely metastasizes. The histologic patterns of these two neoplasms can be similar. Expression of c-kit, a transmembrane receptor tyrosine kinase, has recently been reported to be expressed in ACC but not PLGA. Expression of galectin-3, a nonintegrin beta-galactosidase-binding lectin, has been reported to be significant in PLGA and decreased in ACC.Formalin-fixed paraffin-embedded tissue from 9 ACC and 14 PLGA were immunostained for c-kit and galectin-3. Cases were scored as 1+ (5-25% positive), 2+ (26-50% positive), or 3+ (>50% positive). C-kit was expressed by 100% of ACC (3+: 7 cases; 2+: 1 case; 1+: 1 case) and by 57% of PLGA (2+: 2 cases; 1+: 6 cases). In all but one ACC, c-kit expression was confined to the inner cell layer. C-kit expression was also noted in the intercalated duct epithelium of the salivary glands and the acinar cells of the lacrimal gland. Galectin-3 was expressed in 8 of 9 cases of ACC and 14 of 14 cases of PLGA. The results of this, the first study to compare c-kit and galectin-3 expression in ACC and PLGA, suggest that c-kit expression characterizes ACC, but not PLGA. Galectin-3 immunohistochemistry does not have a role in the differentiation of ACC and PLGA. C-kit immunostaining may be a valuable adjunctive tool for this differential diagnosis, particularly in the setting of a limited biopsy. Our finding of different patterns of c-kit expression in tubular and solid variants of ACC supports the concept of solid variant ACC as a high-grade tumor, with progression toward an entirely "inner cell" phenotype.
Penner
Carla R
CR
Department of Pathology and Laboratory Medicine, Emory University, Atlanta, Georgia 30322, USA.
Folpe
Andrew L
AL
Budnick
Steven D
SD
D000230:Adenocarcinoma / Q000175:diagnosis* / Q000378:metabolism; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers; D003528:Carcinoma, Adenoid Cystic / Q000175:diagnosis* / Q000378:metabolism; D003937:Diagnosis, Differential; D005260:Female; D037502:Galectin 3 / Q000096:biosynthesis; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D019009:Proto-Oncogene Proteins c-kit / Q000096:biosynthesis*; D012468:Salivary Gland Neoplasms / Q000175:diagnosis* / Q000378:metabolism
D015415:Biomarkers; D037502:Galectin 3; D019009:Proto-Oncogene Proteins c-kit