Open AccessP40 expression in small cell lung cancer: The presence of p40‐positive cells does not always indicate squamous differentiation
Author(s) -
Nakajima Naoki,
Yoshizawa Akihiko,
Moriyoshi Koki,
Sonobe Makoto,
Menju Toshi,
Sumiyoshi Shinji,
Date Hiroshi,
Haga Hironori
Publication year - 2019
Publication title -
thoracic cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.823
H-Index - 28
eISSN - 1759-7714
pISSN - 1759-7706
DOI - 10.1111/1759-7714.13062
Subject(s) - medicine , immunohistochemistry , pathology , lung cancer , cytology , biopsy , cancer , h&e stain , staining
Background Small cell lung cancer (SCLC) is normally diagnosed with hematoxylin and eosin stains, although some cases require immunohistochemistry (IHC). P40 is highly sensitive and specific for squamous cell carcinoma and is thus considered the best marker for this cancer. However, the status of p40 expression in SCLC is not well known. The aim of this study was to analyze p40 expression in resected SCLC using IHC. Methods Forty‐four surgically resected SCLC cases were enrolled. Clinical data were obtained from the patients’ medical records. Pathologists blinded to the patients’ clinical data reviewed the SCLC slides. IHC was performed on a representative slide of each case. Results Although p40 was not diffusely expressed in any of the SCLC cases, p40‐positive cells were observed in the tumors in 15 cases (34.1%). Ten of these exhibited p40 in < 1% of tumor cells. In the remaining five cases, 1–5% of tumor cells expressed p40, and in three of these, the cells expressing p40 also expressed TTF‐1 and neuroendocrine markers. There was no statistically significant relationship between p40 positivity and any other clinicopathological characteristics. Conclusions Some resected SCLCs express p40 focally. This result suggests that the presence of positive p40 cells does not exclude a diagnosis of SCLC. Thus, small biopsy or cytology specimens with p40‐positive cells must be diagnosed carefully.