Abstract
Context
In this era of targeted therapy, it is important to distinguish the various subtypes
of nonsmall cell lung carcinoma (NSCC). Diagnosis based on morphology alone is challenging
in poorly differentiated carcinomas and core biopsies. Immunohistochemistry (IHC)
helps in specifying the lineage for the subtype of NSCC. Till date, p63 is the most
frequently used and sensitive marker for squamous cell carcinoma (SQCC). However,
it is not specific and stains a subset of adenocarcinoma (ADC). Thus, a more reliable
and specific marker is required for the diagnosis of SQCC.
Objective
The objective of the study was to validate the diagnostic utility of p40 over p63
in differentiating pulmonary SQCC from ADC and NSCC-not otherwise specified (NOS).
Materials and Methods
A total of 123 cases of NSCC were initially reviewed and subtyped blinded to the results
of IHC. This was followed by a review of IHC slides which included p63, p40, thyroid
transcription factor 1, Napsin-A, cytokeratin (CK) 5/6, and CK7.
Results
There were 64 ADC, 19 SQCC, and 40 NSCC-NOS. IHC helped to confirm the morphological
diagnosis in 62/64 ADCs and19/19 SQCCs. IHC classified the cases of NSCC-NOS into
NSCC favoring ADC – 12 cases, NSCC favoring SQCC – 10 cases, and NSCC favoring AD-SQCC
– 4 cases. Both p63 and p40 showed near equal sensitivity for SQCC (100% and 97%,
respectively), whereas p63 showed far lower specificity when compared to p40 (51.3%
vs. 100%).
Conclusion
The present study confirms and validates that p40 is equally sensitive but highly
specific than p63 in detecting SQCC. Hence, we recommend the routine use of p40 instead
of p63 for the definite categorization of NSCC of the lung.
Keywords
Immunohistochemistry - lung - nonsmall cell carcinoma - p40 - p63
