One of the most difficult aspects of treating cancer is the distinct number of forms it can take. While most cancers follow particular biological patterns, the literature is full of examples that do not follow these general trends. For example, in patients who present with a number of different tumors, metastasis is most often suspected as it is very rare for a single person to have multiple primary tumors at one time. Another relative rarity is for one form of cancer to mimic an entirely different form. Imaging tests and morphology analysis can usually identify the type of cancer present in any one patient, but in some cases, these techniques may not return the proper diagnosis, so immunohistochemical (IHC) analysis may be necessary to properly identify the cancer at hand.

In a recent case study from Japan, doctors describe a man whose presentation violated both of the principles just described. The patient was diagnosed with pseudomesotheliomatous adenocarcinoma of the lung, which is a rare lung cancer that morphologically mimics pleural mesothelioma, as well as squamous cell carcinoma of the esophagus and adenocarcinoma of the stomach.

Case Study

The patient presented as a 78 year-old man with shortness of breath and right chest pain. He was a smoker without known asbestos exposure and while his previous medical history was generally insignificant, his presentation was quite remarkable. A CT scan revealed diffuse pleural thickening in the right thorax and PET showed significant pleural involvement. A biopsy of the pleural mass was performed by video-assisted thoracoscopic surgery (VATS). Pictures from VATS also showed pleural thickening with diffuse spread. All signs pointed to malignant mesothelioma. However, IHC analysis of the biopsy sample revealed adenocarcinoma of the lung, not mesothelioma. The final diagnosis given was pseudomesotheliomatous adenocarcinoma of the lung. This rare form of lung cancer has a similar growth pattern to diffuse malignant mesothelioma and typically shares its poor prognosis as well, with a median survival figure of eight months from diagnosis.

Along with the tests that revealed the pseudomesotheliomatous adenocarcinoma, the patient also underwent an upper gastrointestinal endoscopy, which is a procedure that allows a doctor to view and biopsy the interior lining of the esophagus, the stomach, and the duodenum (the first part of the small intestine). The procedure revealed tumors in the esophagus and the antrum, which is the cavity in the stomach where food collects prior to its passage into the small intestine. Biopsy of each tumor revealed they were separate, primary sites: the esophageal tumor was a squamous cell carcinoma, while the stomach tumor was an adenocarcinoma. Analysis of the stomach tumor and the pleural malignancy showed they, too, were separate primary sites, so metastasis was not involved in any manner with the patient’s presentation.

As there are no treatment guidelines for this combination of cancers, the doctors treated the man in a palliative manner. He died six months after diagnosis, due primarily to heavy tumor growth in the pleural areas.

Conclusion

This patient’s presentation was remarkable for having multiple primary cancers, as well as for one of them being pseudomesotheliomatous adenocarcinoma. When multiple tumors are present, metastasis is nearly always at work. The authors report on a previous study of 5456 autopsy cases that described 285 cases of double primary cancer (5.2%) and only 58 cases of triple primary cancer (1.1%). Immunohistochemical analysis clearly showed three primary cancers in this man, placing him within the 1.1% figure from the previous study. It should be no real surprise then that the authors also state this is the first case in the literature of pseudomesotheliomatous adenocarcinoma concurrent with esophageal cancer and stomach cancer. Pseudomesotheliomatous adenocarcinoma is itself a rare cancer. Morphologically it resembles pleural mesothelioma and its diffuse nature is unlike the majority of other forms of lung cancer, so it’s easy to mistake the one for the other. Immunohistochemical analysis is an effective means of differentiating the two cancers, as each presents with specific markers that IHC can identify. The authors recommend IHC in the diagnosis of any pleural malignancy because of its ability to accurately diagnose the particular cancer involved.

Labels: LungCancer, mesothelioma