Expression of cytokeratin subtypes: MMP-9, p53, and αSMA to differentiate basaloid squamous cell carcinoma from other basaloid tumors of the oral cavity.

Basaloid squamous cell carcinoma (BSCC) is rare variant of oral squamous cell carcinoma (OSCC) with predilection for upper aerodigestive tract. Although it is characterized by distinct histologic features it is often confused with conventional OSCC and other basaloid tumors. The study aims to establish differentiating features of BSCC with oral basaloid tumors using immunohistochemical (IHC) markers. This retrospective study included 34 cases, including BSCC, OSCC, and basaloid tumors. IHC staining was performed with primary antibodies against cytokeratin (CK) 19, 14, 8/18, α-smooth muscle actin (αSMA), p53, and MMP-9. A prominent CK 19, 14, and 8/18 expression was observed in BSCC as compared with basaloid tumors suggesting of basal cell origin with undifferentiated type of tumor cells. Expression of αSMA was intense in tumor cells of myoepithelial differentiation but lacked in BSCC. The intense expression of p53 and MMP-9 was noted in all basaloid malignancies. Considering standard histologic criteria in diagnosing BSCC, when in confusion with other basaloid tumors, IHC markers gain importance. Hence, enhanced expression of CK 19, 8/18, and 14 and coexistence of p53 and MMP-9 expression and negativity for αSMA suggest an accurate diagnosis of BSCC.