1.3 Malignant Effusion – Evidence-Based Diagnosis

An 86-year-old man presents with weight loss for 2 months and worsening shortness of breath for 2 weeks. An x-ray shows a left pleural effusion (fluid around the lung). Tests of that fluid removed with a needle (thoracentesis) show undifferentiated carcinoma. History, physical examination, routine laboratory tests and noninvasive imaging do not disclose the primary cancer. Could “metastatic undifferentiated carcinoma” be a sufficient diagnosis, or are additional studies needed? Does your answer change if he has late-stage Alzheimer’s disease?

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Whether metastatic undifferentiated carcinoma is a sufficient diagnosis depends on what decisions are to be made and how difficult it will be to make a more specific diagnosis. Although we suspect the prognosis is grim no matter what the primary is, it is possible that there are some diagnoses for which he would choose chemotherapy. On the other hand, we did not tell you much about the patient — some 86-year-olds are better candidates for chemotherapy than others, either because of underlying comorbidities or patient preferences.

If this were our family member, and the additional workup was going to be risky or invasive, we would want an estimate of the likelihood that a more strenuous search would identify something for which treatment would be a reasonable option, and how much he might gain from such treatment. The most important thing is to realize that the decision to pursue a more specific diagnosis should be just that — a decision; it should not be automatic.

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