Cytokeratin 7 and 20 staining for the diagnosis of lung and colorectal adenocarcinoma

The origin of metastatic adenocarcinoma lesions can sometimes be difficult to diagnose. The objectives of our study were to establish the cytokeratin staining pattern of primary and metastatic lung and colorectal adenocarcinomas, and to determine if this helps to identify the site of origin of metastatic lesions. We reviewed a total of 102 tissue samples from patients in our tumour registry, with either primary or metastatic lung or colorectal adenocarcinoma. Tissue sections were stained for cytokeratin 7 and 20 and read as positive or negative for staining. Clinical and radiologic information was reviewed from computerised charts. The cytokeratin 7+/cytokeratin 20− pattern characterised 96% (29 out of 30) of primary and 95% (21 out of 22) of metastatic lung adenocarcinomas. All the primary (26), and 88% (21 out of 24) of metastatic colorectal adenocarcinomas stained cytokeratin 7−/cytokeratin 20+. Samples from a variety of metastatic sites were evaluated for cytokeratin 7 and 20 staining. Out of the 102 samples, in 95% (97 out of 102) of the cases, the cytokeratin 7 and cytokeratin 20 staining pattern characterised and differentiated between lung and colorectal adenocarcinoma. Primary and metastatic lung adenocarcinomas show a cytokeratin 7+/cytokeratin 20− staining pattern, while colorectal adenocarcinomas stain cytokeratin 7−/cytokeratin 20+. Cytokeratin staining is helpful in the diagnostic differentiation of metastatic lesions from these two common primaries, and assists in determining the site of origin of metastatic lesions

A Case of Metachronous Metastasis to the Breast from Non-Small Cell Lung Carcinoma

Breast metastases from an extramammary primary tumor are very rare and the prognosis for such patients is generally poor. We report here on a case of a 42-year-old female with metastasis of non-small cell lung cancer to the breast, and she is now being followed up on an outpatient basis. In 2004, she presented with a solitary pulmonary nodule in the left lung, and this lesion had been noted to have gradually increased in size over time. The final pathological diagnosis was adenocarcinoma, and the diagnosis was made by performing percutaneous needle aspiration and lobectomy of the left upper lobe. Adjuvant chemotherapy and radiotherapy were given. Unfortunately, a nodule in the left breast was noted three years later, and metastatic non-small-cell lung cancer to the breast was diagnosed by excisional biopsy. Making the correct diagnosis to distinguish a primary breast carcinoma from a metastatic one is important, because the therapeutic plan and outcome for these two types of cancer are quite different