This essay argues that the emotional rhetoric of today's breast cancer discourse-with its emphasis on stoicism and 'positive thinking' in the cancer patient, and its use of sympathetic feeling to encourage charitable giving-has its roots in the long 18th century. While cancer had long been connected with the emotions, 18th-century literature saw it associated with both 'positive' and 'negative' feelings, and metaphors describing jealousy, love and other sentiments as 'like a cancer' were used to highlight the danger of allowing feelings-even benevolent or pleasurable feelings-to flourish unchecked. As the century wore on, breast cancer in particular became an important literary device for exploring the dangers of feeling in women, with writers of both moralising treatises and sentimental novels connecting the growth or development of cancer with the indulgence of feeling, and portraying emotional self-control as the only possible form of resistance against the disease. If, as Barbara Ehrenreich suggests, today's discourse of 'positive thinking' has been mobilised to make patients with breast cancer more accepting of their diagnosis and more cooperative with punitive treatment regimens, then 18th-century fictional exhortations to stay cheerful served similarly conservative political and economic purposes, encouraging continued female submission to male prerogatives inside and outside the household.