Large cell neuroendocrine carcinoma (LCNEC) of the lung is a new entity. Besides morphological characteristics, its molecular biological features have been investigated by many researchers and compared to those of other neuroendocrine carcinomas, small cell lung carcinoma (SCLC) and carcinoid tumor (CT). However, there are few reports that show the significantly different genetic characteristics between them. The purpose of the present paper was to study the frequency of loss of heterozygosity (LOH) at chromosome 3p (3p14.2) in 38 neuroendocrine carcinomas of the lung (13 LCNEC, 11 SCLC and 14 CT) and 10 large cell carcinomas (LCC). The frequencies of LOH at 3p14.2 were 69.2% in LCNEC, 81.8% in SCLC, 50.0% in LCC and 7.14% in CT. Those at 22q13.3 were 30.8% in LCNEC, 72.7% in SCLC, 45.5% in LCC and 7.14% in CT. In particular, the frequency of SCLC with LOH at both 3p14.2 and 22q13.3 (63.6%) was significantly higher than that of LCNEC (15.4%). LCNEC and SCLC had different characteristics of LOH patterns at 3p14.2 and 22q13.3. The combined analysis of the LOH at 3p14.2 and 22q13.3 is thought to be useful for differential diagnosis between LCNEC and SCLC.
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