THE PROGNOSTIC AND DIFFERENTIAL DIAGNOSTIC VALUE OF CYTOKERATIN 7 AND 19, AND THYROID TRANSCRIPTION FACTOR-1 EXPRESSION IN LUNG NEUROENDOCRINE TUMORS OF VARIOUS GRADES

Abstract

Background: Neuroendocrine tumors of the lung (NETL) are a wide range of tumors with various malignancy grades and prognosis. Despite their prevalence being 20 to 25% of all lung cancers, many aspects that impact their clinical course and prognosis are not well understood. Aim – to identify morphological and immunophenotypic characteristics of various NETL types would that more accurately reflect their biological potential and allow for prediction of their unfavorable clinical outcomes. Materials and methods: We performed immunohistochemical assessment of the diagnostic biopsies and surgical specimens from 152 patients with NETL aged 53 ± 13 years and identified 49 typical carcinoids, 32 atypical carcinoids, 60 small cell neuroendocrine carcinomas and 11 large cell neuroendocrine carcinomas, which accounted for 32.2, 21.1, 39.5 and 7.2%, respectively. Markers of neuroendocrine differentiation, such as synaptophysin, chromogranin A and CD56, as well as cytokeratins 7 and 19, thyroid transcription factor-1 (TTF-1), and Ki67 were used. The results were analyzed with analysis of variance (ANOVA), chi-square test (χ²), and post-hoc comparisons with the Bonferroni correction. Results: Most often, the expression of cytokeratins 7 and 19 was found in large cell neuroendocrine carcinoma (72.7 and 90.9%, respectively), less frequently, in atypical carcinoids and small cell neuroendocrine carcinomas (50 and 53.3%; 41.7 and 64.6% of cases, respectively), whereas in typical carcinoids it was rare (5.9 and 15.9%, respectively). The rates of cytokeratin 7 and 19 expression were significantly lower in the typical carcinoids, compared to the atypical carcinoids, small cell neuroendocrine carcinomas and large cell neuroendocrine carcinomas (р < 0.05, χ²). The expression of cytokeratin 19 was significantly more common for large cell neuroendocrine carcinomas, than for small cell neuroendocrine carcinomas and atypical carcinoids (р < 0.01, χ²). The expression of TTF-1 was very rare in the typical carcinoid cells (6.5% of cases) and significantly more often in atypical carcinoids (61.5%) and in small cell neuroendocrine carcinomas and large cell neuroendocrine carcinomas (82.7 and 77.8% of cases, respectively). TTF-1 expression was significantly less frequent in typical than in atypical carcinoids, small cell neuroendocrine carcinomas and large cell neuroendocrine carcinomas (р < 0.01, χ²). The mean index of tumor cell proliferation (Ki67) was the lowest in typical carcinoids (2.6%), amounted to 12% in atypical carcinoids, to 44% in large cell neuroendocrine carcinomas and reached the maximum of 61% in small cell neuroendocrine carcinomas. There were significant differences in the mean Ki67 index in the NETL 4 groups (р < 0.001, ANOVA). Conclusion: Expression of TTF-1, cytokeratin 7 and 19 in the neuroendocrine tumors of the lung is characteristic for a less differentiated cell immunophenotype and allows for identification of the risk group with unfavorable clinical outcome among low-grade typical and atypical carcinoids.