[1179] Significance of Ki-67 and p53 Immunoexpression in the Differential Diagnosis of Oral Necrotizing Sialometaplasia and Squamous Cell Carcinoma.

Tahereh Dadfarnia, Basim Mohammad, Mahmoud A Eltorky. UTMB, Galveston, TX

Background: Necrotizing sialometaplasia (NS) is a benign inflammatory condition that usually involves the salivary glands in hard palate. It may be mistaken for a malignant neoplasm, such as invasive squamous cell carcinoma (SCC) as well as mucoepidermoid carcinoma. Despite the presence of some characteristic features that help distinguish NS from SCC on the H&E slides, some cases of NS with extensive pseudoepitheliomatous hyperplasia and reactive atypia of squamous epithelium with necrosis are often difficult to differentiate from invasive SCC; hence, the application of immunohistochemistry has been attempted and proposed as an adjunct to diagnosis. In this study, we have demonstrated that p53, and Ki-67 staining may assist in the diagnosis of NS from SCC.
Design: Thirteen cases of NS, sixteen cases of well-differentiated and four moderately-differentiated invasive SCC related H&E slides in the head and neck with their matched tissue blocks were randomly selected from our surgical pathology archive from 1992 to 2009. Each case was stained with Ki67, p53, BCL-2, p16 and EGFR antibodies. The cases were reviewed by two pathologists independently.
Results: All thirteen cases of NS were negatively stained for BCL-2 and EGFR. Ki-67 staining was negative in all cases with only scattered nuclear staining in <10% of cells. Three cases (23%) showed weak and focal positive nuclear staining for p53. Two cases (15%) showed positive staining for p16. In sixteen well-differentiated SCC cases, p53 was considered focally & weakly positive in one patient (6%) and strongly positive in eleven patients (69%). BCL-2, p16, EGFR were positive in three cases (18%) and Ki-67 was positive with high nuclear staining >35% in all cases. In four moderately-differentiated SCC cases, P53 expression was positive in all cases. Two tumors (50%) had a positive expression of BCL-2. Three cases (75%) had a positive p16 staining and one (25%) had a positive EGFR staining. All cases were positive with high nuclear staining >35% of cells for Ki-67. The ki-67 and p53 is generally more intense and is increased in higher grade of malignancy. The BCL-2, EGFR and p16 had the same pattern of staining with the same extent in NS and SCCs.
Conclusions: The diagnosis of NS may be difficult and is reliant upon a properly oriented section and a clinical history. Diagnosis may be supplemented via immunohistochemistry, demonstrating focal or absent immunoreactivity for p53, low to absent immunoreactivity for Ki-67 (<10% of cells). These findings may be helpful in confirming the diagnosis of NS in the appropriate clinical setting.
Category: Head & Neck

Tuesday, March 1, 2011 1:00 PM

Poster Session IV # 135, Tuesday Afternoon


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