ulcus induratum

例句：

1. 1. The doctor found a hard lump under his fingernail.
   医生在他的指甲下发现了一个硬块。
2. 2. This is the first time I've seen such a large ulcer.
   这是我第一次看到这么大的溃疡。
3. 3. Ulcers can be caused by various factors, including stress and poor diet.
   溃疡可以由各种因素引起，包括压力和不良饮食。