I have a 7 month male lamb (half Rambouillet, half Suffolk) that has a big lump in its neck.
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http://imgur.com/a/gwDUfI does not seem to know it has it, eats and drinks fine, and sounds fine

It appears to be perfectly centered in the neck, so it seems physiologic, but it is not high enough to be a goiter I think.
It is spongy, like soft cheese maybe. I only have this and a ewe and a ram I inherited from someone who didn't want them any more.
Any thoughts?