[1909] p53 Immunostaining Should Be Used in Conjunction with p16 in Differentiating Metastatic Cervical Squamous Cell Carcinoma Involving the Lung from Primary Lung Squamous Cell Carcinoma

Daichi Maeda, Tomoko Inoue, Shigeki Morita, Masashi Fukayama. Graduate School of Medicine, University of Tokyo, Tokyo, Japan

Background: Histological distinction between primary lung squamous cell carcinoma (PLSCC) from metastatic uterine cervical squamous cell carcinoma involving the lung (MCSCCL) is often difficult. In this study, we evaluated the utility of p16 and p53 immunohistochemistry in distinguishing MCSCCL from PLSCC.
Design: A total of 40 cases of female lung SCC (29 cases with no past history of other primaries including cervical cancer [definite PLSCC] and 11 with a past history of cervical cancer [possible MCSCCL]), and 31 cases of primary invasive uterine cervical SCC (PCSCC) were retrieved from the archive of the Department of Pathology of the University of Tokyo Hospital. Immunohistochemistry for p16 and p53 were performed. First, we compared the immunophenotypes of definite PLSCCs and PCSCCs. Next, we applied the panel to the “possible MCSCCL” group to examine its utility.
Results: Diffuse (≥90%) p16 immunoreactivity positivity was observed in 29/31 (94%) of PCSCCs and 7/29 (24%) of definite PLSCCs. Diffuse p53 positivity (≥90%) was observed specifically in definite PLSCCs (48%; 14/29 cases). None of the PCSCCs showed diffuse overexpression of p53.

p16 and p53 expression in primary lung SCC and primary cervical SCC
 p16p53
 PLSCC (n=29)PCSCC (n=31)PLSCC (n=29)PCSCC (n=31)
<4%13 (45%)0 (0%)11 (38%)22 (71%)
5-14%1 (3%)0 (0%)2 (7%)8 (26%)
15-49%3 (10%)0 (0%)1 (3%)1 (3%)
50-89%5 (17%)2 (6%)1 (3%)0 (0%)
≥90%7 (24%)29 (94%)14 (48%)0 (0%)
PLSCC; primary lung squamous cell carcinoma, PCSCC; primary cervical squamous cell carcinoma

The p16 (diffusely postive) / p53 (negative or focally positive) phenotype was observed in 94% of PCSCCs, whereas only 7% of definite PLSCCs revealed such phenotype. Of the 11 cases of possible MCSCCLs, 9 showed the p16 (diffusely positive) / p53 (negative or focally positive) phenotype and two showed the p16 (negative or focally positive) / p53 (negative or focally positive) phenotype.
Conclusions: Because a significant proportion (24%) of PLSCCs showed diffuse p16 immunoreactivity, we conclude that p16 should not be used as a sole marker to distinguish PLSCC from MCSCCL. Immunohistochemistry for p53 should be applied in adjunction because diffuse p53 positivity occurs specifically in PLSCC. By applying the p16 / p53 panel, we were able to assume that 2 cases of the lung SCC with a past history of cervical cancer were most likely PLSCCs.
Category: Pulmonary

Wednesday, March 6, 2013 1:00 PM

Poster Session VI # 299, Wednesday Afternoon

 

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