Neuroendocrine tumors of the lung (NETL) are a wide range of tumors with various malignancy grades and prognosis.
We performed immunohistochemical assessment of the diagnostic biopsies and surgical specimens from 205 patients with NETL aged 55614 years and identified 61 (29,8%) typical carcinoids (TC), 44 (21,5%) atypical carcinoids (ATC), 84 (41%) small cell neuroendocrine carcinomas (SCNEC) and 16 (7,8%) large cell neuroendocrine carcinomas (LCNEC). Markers of neuroendocrine differentiation (synaptophysine, chromogranine A and CD56) and cytokeratins (CK) 7 and 19, thyroid transcription factor-1 (TTF-1), CD117 were used.
Most often, the expression of CK7 and CK19 was found in LCNEC (71.4%, 10/14 and 91.7%, 11/12 respectively), less frequently, in ATC and SCNEC (52,8%, 19/36 and 52.4%, 22/42; 43,9%, 29/66 and 68,2%, 45/66 of cases, respectively), whereas in TC it was rare (13,3%, 6/45 and 19,3%, 11/57 espectively). The rates of CK7 and 19 expression were significantly lower in the TC, compared to the SCNEC and LCNEC (h<0.01, v.) The expression of TTF-1 was very rare in the TC (11,6%, 5/43 of cases) and significantly more often in ATC (60.5%, 23/38) and in SCNEC and LCNEC (79,2%, 57/72 and 75%, 9/12 of cases, respectively). TTF-1 expression was significantly less frequent in typical than in ATC, SCNEC and LCNEC (h < 0.01, v.). The expression CD117 was absent in the TC (0%, 0/27), very rare in the ATC (17,4%, 4/23) and significantly more often in SCNEC and LCNEC (95,7%, 43/47 and 42,8%, 3/7 of cases, respectively).
Expression of TTF-1, CK7, 19 and CD117 in the NETL is characteristic for a less differentiated cell immunophenotype and allows for identification of the risk group with unfavorable clinical outcome among low-grade TC and ATC.