Expression of p53 in adenoid cystic carcinoma of salivary glands – a clinicopathological and immunohistochemical correlation

Abstract

Objective: To document p53 protein expression in Adenoid cystic carcinoma (AdCC) of salivary glands and correlate this expression with clinicopathological parameters in prognostic assessment of AdCC at microscopic level.

Patients & Methods: This Correlation study was carried out at Armed Forces Institute of Pathology (AFIP), Rawalpindi for 6 months. A total of 40 cases of AdCC diagnosed in salivary glands of five years duration (2006-2010) were retrieved from tumor registry. Clinical information was extracted from histopathology request forms submitted with the specimens. Fresh slides were prepared for histopathological (H&E staining) 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 of patients were male (n=27, 67.5%), among which 17 yielded positive while 10 had negative p53 expression. Among tumors evolving from major salivary glands (n=13), 10 showed positive whereas only 3 displayed negative results for p53 expression. Maximum number 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 having positive while 14 were having negative p53 expression. Lymphovascular invasion was present in 37 (92.5%) cases, among which 22 yielded positive while 15 had negative expression of p53.

Conclusion: 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. Though none of the correlation turned out as statistically significant to be used as key element in prognostic assessment of AdCC at microscopic level, however the above mentioned parameters can be considered important while planning the management which may need an aggressive approach in these cases. There is a need of more research for additional comprehensive  prognostic assessment of salivary gland AdCC.

Keywords: Adenoid cystic carcinoma, salivary glands, p53, clinicopathological parameters.