Identification of the most specific markers to differentiate primary pulmonary carcinoma from metastatic gastrointestinal carcinoma to the lung

Diagnostic gastrointestinal markers in primary lung cancer and pulmonary metastases

Histopathological diagnosis of pulmonary tumors is essential for treatment decisions. The distinction between primary lung adenocarcinoma and pulmonary metastasis from the gastrointestinal (GI) tract may be difficult. Therefore, we compared the diagnostic value of several immunohistochemical markers in pulmonary tumors. Tissue microarrays from 629 resected primary lung cancers and 422 resected pulmonary epithelial metastases from various sites (whereof 275 colorectal cancer) were investigated for the immunohistochemical expression of CDH17, GPA33, MUC2, MUC6, SATB2, and SMAD4, for comparison with CDX2, CK20, CK7, and TTF-1. The most sensitive markers for GI origin were GPA33 (positive in 98%, 60%, and 100% of pulmonary metastases from colorectal cancer, pancreatic cancer, and other GI adenocarcinomas, respectively), CDX2 (99/40/100%), and CDH17 (99/0/100%). In comparison, SATB2 and CK20 showed higher specificity, with expression in 5% and 10% of mucinous primary lung adenocarcinomas and both in 0% of TTF-1-negative non-mucinous primary lung adenocarcinomas (25-50% and 5-16%, respectively, for GPA33/CDX2/CDH17). MUC2 was negative in all primary lung cancers, but positive only in less than half of pulmonary metastases from mucinous adenocarcinomas from other organs. Combining six GI markers did not perfectly separate primary lung cancers from pulmonary metastases including subgroups such as mucinous adenocarcinomas or CK7-positive GI tract metastases. This comprehensive comparison suggests that CDH17, GPA33, and SATB2 may be used as equivalent alternatives to CDX2 and CK20. However, no single or combination of markers can categorically distinguish primary lung cancers from metastatic GI tract cancer.

CK-7 negative primary lung adenocarcinoma

Cytokeratin (CK) 7 is normally expressed in the vast majority of lung adenocarcinoma (ADC). However, on rare occasions, as reported in this paper, CK7 negativity can challenge the diagnosis of pulmonary ADC. Hence, the need to use a combination of 'immunomarkers' such as thyroid transcription factor 1, Napsin A, p40, p63 and CK20.

Cetuximab and Dabrafenib Plus Trametinib for Untreated Colonic Metastasis of BRAFV600E Mutant Primary Lung Adenocarcinoma with Signet Ring Cell Features: An Interesting and Rare Case Report

Colonic metastases of lung adenocarcinoma are extremely rare. Signet ring cell adenocarcinoma (SRCA) has not been described in patients with gastrointestinal metastasis of lung adenocarcinoma. SRCA is a unique subtype of adenocarcinoma with strong invasion and a poor prognosis, and most SRCA found in the lung are due to gastrointestinal metastases. This report describes a rare case of colonic metastasis from primary lung SRCA. A 64-year-old female was admitted to Sun Yat-sen University Cancer Center for feeling of nausea and malaise. Following a positron emission tomography CT (PET-CT) scan, widespread metastases of tumor cells were found in the bilateral lung, liver, bone, and multiple lymph nodes, but there was no evidence of metastasis to the colon. Two months later, the patient received a liver biopsy at Tongji Hospital in Wuhan. Pathology revealed a poorly differentiated adenocarcinoma with SRCA conformation, but immunohistochemical staining did not identify the original source of tumor cells. Considering that SRCA mainly derives from the gastrointestinal tract and that serum gastrointestinal tumor markers were elevated, we performed gastrointestinal endoscopy on the patient. The results showed an isolated polyp in the colon, and the pathology results indicated a poorly differentiated adenocarcinoma that was considered to originate from the lung based on immunohistochemical staining. Meanwhile, genetic tests identified a BRAF V600E mutation. The final diagnosis was colonic metastasis of BRAFV 600E mutated lung SRCA. Considering the positive expression of EGFR in this case, cetuximab was innovatively added to the first-line treatment regime (dabrafenib and trametinib). To date, the patient has received thirty-two weeks of treatment. Interestingly, lung and liver tumors shrank and tumor markers in the blood normalized. Our findings offer valuable diagnostic and therapeutic information for colonic metastasis of BRAFV600E mutant primary lung adenocarcinoma with signet ring cell features.