DIAGNOSTIC INDICATORS IN ADENOID CYSTIC CARCINOMA OF SALIVARY GLANDS – A CLINICOPATHOLOGICAL AND IMMUNOHISTOCHEMICAL CORRELATION

Objectives: To document p53 protein expression in Adenoid cystic carcinoma (AdCC) of salivary glands and to correlate this expression with clinicopathological parameters in prognostic assessment of AdCC at microscopic level.
Methods: A total of 40 cases of diagnosed salivary AdCC were retrieved from tumor archives of AFIP, Rawalpindi along with their paraffin blocks from year 2006-2010. Clinical information was extracted from histopathology request forms. Fresh slides were prepared for histopathological and subsequent p53 immunohistochemical evaluation.
Results: Out of 20 patients (50%) belonging to 31-50 years age category, 12 were positive and 8 cases were negative for p53 expression. Majority were males (n=27, 67.5%), among which 17 yielded positive while 10 had negative p53 expression. Minor salivary gland tumors (n=27,67.5%) demonstrated equivocal results with 14 as p53-positive while 13 as p53-negative. Among major salivary glands tumors (n=13), 10 showed positive whereas only 3 displayed negative results for p53 expression. Majority of tumors (n=17, 42.5%) were greater than 4 cm in size with 12 of them as p53-positive and 5 as p53-negative. Results for histopathological subtype and tumor grade were similar, with 34 (85%) revealing cribriform growth pattern, thus having grade II neoplasms, with equivocal p53 staining, yielding 18 as p53-positive and 16 as p53-negative neoplasms in each parameter. Though small in count, all tumors with solid histological subtype (n=5,13%), hence with grade III neoplasms exhibit positive p53 expression. Perineural invasion was present in 77% (n=31) of tumors, among which 17 were positive while 14 were negative for p53 expression. Lymphovascular invasion was present in 37 (92.5%) of cases, among which 22 yielded positive while 15 had negative expression of p53.
Conclusions: Tumors with larger size (≥4cm), solid growth pattern, grade III neoplasm and major salivary gland as primary tumor site bear positive correlation with p53 protein expression, but none of the correlation turned out as statistically significant to be used as key element in prognostic assessment of AdCC at microscopic level.