Are you unsure about what to write in the gift card message? Here are a few links to websites for some inspiration:
By occasion
http://southnfrance.com/gift-message-suggestions/
Funny empathy cards for serious illnesses
http://info.emilymcdowell.com/empathy-cards-for-serious-illness/
Cancer support
http://www.huffingtonpost.com/nikhil-joshi/10-things-to-not-say_b_5296916.html?utm_hp_ref=generation-why
http://www.cancer.org/treatment/understandingyourdiagnosis/talkingaboutcancer/whensomeoneyouknowhascancer/when-somebody-you-know-has-cancer-ways-to-respond
http://www.thesilverpen.com/breast-cancer-information-facts/how-to-help-someone-who-has-cancer/what-to-say-to-someone-with-cancer/
Condolences
http://www.acknowledgements.net/wordsofsympathy.htm