A case report of successful diagnosis of a pulmonary nodule by a survey of oncogenic mutations; primary lung carcinoma or pulmonary metastasis?

Abstract

Introduction: The number of patients diagnosed with solid carcinomas is increasing, and the most common site of metastasis is the lungs. It is often difficult to make a differential diagnosis between primary lung carcinoma and metastatic lung tumor in using histological examination and by determining their immunohistological status.

Presentation: A 64-years-old man presented with dyspnea with chest computed tomography (CT) findings of a pulmonary tumor, and afterwards suffered from a sudden bowel hemorrhaged due to colorectal carcinoma. The histological diagnosis of a pulmonary tumor was poorly differentiated adenocarcinoma. Both Thyroid transcription factor-1 (TTF-1) and Cytokeratin20 (CK20) were immunohistologically negative. Of the some oncogenic mutations investigated, a neuroblastoma RAS viral oncogen homolog (NRAS) codon13 G13D mutation was detected in both the colorectal carcinoma and the pulmonary tumor tissue samples. Based on the result, the pulmonary tumor was diagnosed as a metastasis derived from colorectal carcinoma.

Discussion: Recently, examination of the oncogenes of solid carcinomas has been clinically investigated in primary lung caricnoma and in colorectal carcinomas. The clinical advantage of the oncogenic mutation survey is to identify the site, and the type, of amino acid change in detail. This case is a rare successful case of a survey of the oncogenes for giving a differential diagnosis.

Conclusion: A survey of the oncogenic genes is very useful to make a differential diagnosis between primary lung carcinoma and metastatic lung tumor.

Keywords: Colorectal carcinoma; Metastatic lung tumor; Mutation; NRAS; Primary lung carcinoma.

Fig. 1

Panel A: Colonoscopy revealed a bowel hemorrhage from the colorectal carcinoma. Panel B: Hematoxylin-eosin stain showed well-to-moderately differentiated tubular adenocarcinoma. (×200).

Fig. 2

Panel A: Chest X-ray revealed the right tumor and the infiltration shadows around the tumor. Panel B, and C and D: Chest CT revealed a pulmonary tumor(C and D; red arrows), hilar (D; yellow arrowheads) and mediastinal (B and C; red arrowheads) lymphadenopathy is enhanced by contrast medium.

Fig. 3

Panel A: Bronchoscopy revealed the tumor in the segmental bronchus B5 of the right middle lobe. There was no finding of hemorrhage from the pulmonary tumor. Panel B: Hematoxylin-eosin stain shows poorly differentiated adenocarcinoma (×200). Panel C and D: Immunohistological staining showed that both TTF-1 (C) and CK20 (D) are negative in the pulmonary tissue sample (×200).