18052 Background: Bevacizumab in combination with carboplatin and paclitaxel improves overall response and survival in patients with advanced or recurrent non-small cell lung carcinoma. However, this drug is not recommended in patients with carcinomas with squamous differentiation. Therefore, identification of squamous cell component is desirable. In many instances, cytology is the diagnostic tool of choice; however, routine cytomorphology is limited in classification of non small-cell carcinomas into squamous and non-squamous subtypes. The aim of this study is to identify the value of immunocytochemistry for p63 in this distinction. Methods: Review of cytology records identified 51 consecutive pulmonary specimens with the diagnosis of non-small cell carcinoma (9 squamous cell carcinomas and 42 carcinomas without squamous differentiation). Histologically, they proved to be 26 squamous cell carcinomas and 25 non-small cell carcinomas without squamous differentiation. P63 immunocytochemical stain was performed on archival alcohol-fixed Papanicolaou stained cytology slides, using standard immunocytochemical methods. Results: Twenty-three (88 %) of the 26 histologically proven squamous cell carcinomas were positive for p63 on cytologic smears. Using p63, we detected 14 carcinomas with squamous differentiation not identified by cytomorphology. Smears from all carcinomas with squamous differentiation were positive for p63. Sensitivity of cytology for the detection of squamous differentiation increased from 35% to 88% using p63 immunocytochemistry (p=0.001, McNemar’s test). Four carcinomas with squamous differentiation were detected only in cytologic and not in corresponding histologic samples. Conclusions: 1- p63 is a useful marker for the detection of squamous differentiation in cytologic pulmonary samples; 2- p63 immunocytochemistry significantly increases the sensitivity for the identification of squamous cell carcinomas of lung from 35% to 88% (p=0.001); 3- p63 immunocytochemistry should be used in all pulmonary cytologic samples with a diagnosis of non-small cell carcinoma to improve therapeutic selection of patients; 4- Cytologic sampling may provide better representation of tumor subtypes. No significant financial relationships to disclose.
Squamous cell carcinoma mimics small cell carcinoma of the lung: a case report
