عَنْ عُقْبَةَ بْنِ عَامِرٍ رَضِيَ اللَّهُ عَنْهُ أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ قَالَ الْمَيِّتُ مِنْ ذَاتِ الْجَنْبِ شَهِيدٌ
It is narrated from Sayyiduna Uqbah bin Amir (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: Whoever dies from internal boils (such as cancer and tumors, etc.) is a martyr.