Which of the following could indicate cancer in a patient with weight loss?

Night sweats can be a significant indicator of an underlying malignancy, particularly in conjunction with weight loss. This symptom, characterized by excessive sweating during sleep, can be associated with certain types of cancers such as lymphoma and leukemia. The presence of night sweats, combined with unexplained weight loss, may suggest that the body is reacting to a neoplastic process or an increase in metabolic demands due to cancer progression.

In contrast, an increased appetite would typically not be associated with cancer; it could indicate other conditions such as hyperthyroidism or even psychological factors. A cough might signal various respiratory conditions or infections but is less specific for cancer without additional context such as the type of cough or presence of other specific symptoms, like hemoptysis. Fatigue is indeed a common symptom in many conditions, including cancer, but on its own is not as specific for cancer when compared to the hallmark combination of night sweats in the setting of significant weight loss.