Utility and pitfall of Immunohistochemistry in the Differential Diagnosis between Epithelioid Mesothelioma and Poorly Differentiated Lung Squamous Cell Carcinoma

Histopathology 2016 September 2 [Epub ahead of print] [Link]

Kushitani K, Amatya VJ, Okada Y, Katayama Y, Mawas AS, Miyata Y, Okada M, Inai K, Kishimoto T, Takeshima Y


The aim of this study was to clarify the usefulness of immunohistochemistry in the differential diagnosis of epithelioid mesothelioma with solid growth pattern (solid epithelioid mesothelioma; SEM) and poorly differentiated squamous cell carcinoma (PDSCC), and to confirm a specific type of antibody panel. Additionally, we aimed to clarify the pitfalls of immunohistochemical analyses.
Formalin-fixed paraffin-embedded specimens from 36 cases of SEM and 38 cases of PDSCC were immunohistochemically examined for calretinin, podoplanin (D2-40), Wilms’ tumour gene product (WT1), cytokeratin (CK) 5/6, p40, p63, carcinoembryonic antigen (CEA), epithelial-related antigen (MOC31), claudin-4, thyroid transcription factor (TTF-1), and napsin A. WT1 showed the highest diagnostic accuracy (85.1%) as a mesothelial marker, and CEA, p40, and Claudin-4 showed higher diagnostic accuraciess (95.9%, 94.6%, and 93.2%) as carcinoma markers. Calretinin (diagnostic accuracy: 75.7%), D2-40 (diagnostic accuracy: 67.6%), CK5/6 (diagnostic accuracy: 63.5%), TTF-1 (diagnostic accuracy: 55.4%), and napsin A (diagnostic accuracy: 52.7%) could not differentiate between SEM and PDSCC. Among these markers, combination of calretinin and WT1 showed the highest diagnostic accuracy (86.5%) as positive markers, and combination of p40 and CEA showed the highest diagnostic accuracy (97.3%) as negative markers. Combination of CEA and claudin-4 also showed relatively high diagnostic accuracy (94.6%) as negative markers.
We recommend the combination of WT1 and calretinin as positive makers, and CEA and claudin-4 as negative markers for differential diagnoses of SEM and PDSCC.