Roles of Immunohistochemical Staining in Diagnosing Pulmonary Squamous Cell Carcinoma

Background: Differentiating morphologic features based on hematoxylin-eosin (HE) staining is the mostcommon method to classify pathological subtypes of non-small-cell lung cancer (NSCLC). However, its accuracyand inter-observer reproducibility in pathological diagnosis of poorly differentiated NSCLC remained to beimproved. Materials and
Methods: We attempted to explore the role of immunohistochemistry (IHC) stainingin diagnosing pulmonary squamous cell carcinoma (SQCC) with poorly differentiated features by HE stainingor with elevated serum adenocarcinoma-specific tumor markers (AD-TMs). We also compared the differenceof epidermal growth factor receptor (EGFR) mutation rate between patients with confirmed SQCC and thosewith revised pathological subtype. Logistic regression analyses were used to test the association between differentfactors and diagnostic accuracy.
Results: A total of 132 patients who met the eligible criteria and had adequatespecimens for IHC confirmation were included. Pathological revised cases in poor differentiated subgroup,biopsy samples and high-level AD-TMs cases were more than those with high/moderate differentiation, surgicalspecimens and normal-level AD-TMs. Moreover, biopsy sample was a significant factor decreasing diagnosticaccuracy of pathological subtype (OR, 4.037; 95% CI 1.446-11.267, p=0.008). Additionally, EGFR mutationrate was higher in patients with pathological diagnostic changes than those with confirmed SQCC (16.7% vs4.4%, p=0.157).
Conclusions: Diagnosis based on HE staining only might cause pathological misinterpretationin NSCLC patients with poor differentiation or high-level AD-TMs, especially those with biopsy samples. HEstaining and IHC should be combined as pathological diagnostic standard. The occurrence of EGFR mutationsin pulmonary SQCC might be overestimated.