The pitfalls in cytology diagnosis of poorly differentiated neuroendocrine carcinoma of lung and their treatment response

Context: Lung is the most common site of small cell carcinoma (SCLC) - a poorly differentiated neuroendocrine carcinoma (PDNEC). SCLC comprises 15-20% of the invasive cancers of the lung. Aim: This study was conducted to appraise the accuracy and pitfalls of the diagnosis of PDNEC on cytology along with treatment responses if available. Settings and Design: Retrospective study for 2 years yielded 21 cases on cytology. Subjects and Methods: Slides of fine-needle aspiration of lymph nodes, the tumor, bronchial brush, and bronchoalveolar lavage specimens were used. The histological correlation was obtained as were treatment responses. Results: Eighteen SCLCs were confirmed on review. Of these, 13 initial reports were concordant and five, discordant. The rest three cases which initially reported as SCLC were found to be negative (2) and combined SCLC (1). One SCLC with concordant initial and reviewed diagnoses failed to confirm on histopathology. The patients, all heavy smokers, were predominantly males in the seventh to eighth decade age group. The sensitivity and specificity of reviewed diagnoses were better than that of the original. The difference between histopathology and cytology diagnoses (reviewed and original) was statistically insignificant. All patients were categorized as 'extensive stage' by positron emission tomography-computerized tomography, and five were treated with etoposide and cisplatin with/without radiotherapy. Conclusion: Age group (61-70) and gender (males) distribution were statistically significant. Intermediate variants of SCLC may be misdiagnosed as adenocarcinoma. Similarly, combined SCLC may be missed on cytology if the observer does not sustain a high index of suspicion. Unequivocal cytology diagnosis opposed to negative histopathology report demands repeat biopsy.