My friend had Dupuytrens Contracture and it does start with a thickening and then a pulling in of one (or two) fingers eventually. She has just had an op for it.
For clarification....if the "lump" is the only feature with no contracture of the fingers.....usually the ring finger it is a nodule in the tendon.
It may stay like that for ever.......a nodule.
However if the nodule gets larger and drags the fingers across the palm (usually the ring finger) ........it is known as Dupytren's Contracture...Mrs Thatcher had it.
No contracture.............a nodule.
Contracture......Dupytren's Contracture.