Napsin A expression in small cell carcinoma of the lung: A cytologic study with review of differentials

Kim HooKim, Sravankumar Kavuri, Scott R. Lauer, Cynthia Cohen, Michelle D. Reid

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Introduction: Napsin A is a diagnostic marker for pulmonary adenocarcinoma and a useful alternative to thyroid transcription factor 1 (TTF-1). TTF-1 also stains pulmonary small cell carcinoma (SCCA). Napsin A expression in SCCAs is not as established as it is in non-SCCAs. We analyzed napsin A and TTF-1 expression in 36 previously confirmed cytologic cases of pulmonary SCCA. Ours is currently the largest cytologic series of such cases examined for napsin A expression. Materials and Methods: Thirty-six patients, (20 men, 16 women), age 43-87 years, mean 57 years, had primary or metastatic pulmonary SCCA diagnosed by fine-needle aspiration biopsies of mediastinum (n = 5); liver (n = 3); subcutaneous nodule (n = 1); lung (n = 6); and axillary, cervical, and mediastinal lymph nodes (n = 20), as well as a pleural effusion (n = 1). Napsin A and TTF-1 expression was tested. Also, previous expression (or lack thereof) with immunocytochemical stains pancytokeratin and neuroendocrine markers (synaptophysin, chromogranin, and cluster of differentiation marker CD56) were noted. Results: All cases of pulmonary SCCA were positive for pancytokeratin. TTF-1 was positive in 35 of 36 cases (97%), and napsin A was negative in all 36 cases (100%). All 36 cases expressed ≥ 1 neuroendocrine marker, including the TTF-1 negative case. Conclusions: This study showed napsin A was negative in all pulmonary SCCAs. This stain may prove to be a useful exclusionary marker in distinguishing pulmonary SCCA from other poorly differentiated lung carcinomas with similar morphologic features, especially those with concomitant TTF-1 expression.

Original languageEnglish (US)
Pages (from-to)90-95
Number of pages6
JournalJournal of the American Society of Cytopathology
Issue number2
StatePublished - Mar 2014


  • Cytology
  • Lung
  • Napsin A
  • Small cell carcinoma
  • Thyroid transcription factor1

ASJC Scopus subject areas

  • Pathology and Forensic Medicine


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