I read your question carefully and I understand your concern. I imagine you are a little irritated of it not having been diagnosed on first MRI. One explanation might be that the 2nd MRI unlike the 1st included contrast administration and that evidenced the tumor. Contrast sequences aren t always done, not considered necessary for a concussion. Also there are some special sequences for pituitary gland and they are done only when there is a clinical suspicion not for concussion evaluation. Another explanation may be simply that it was missed. When the radiologist evaluates the MRI he pays more attention to certain things depending on indication and pituitary gland is not an area commonly involved by trauma, so small things may have been missed if one doesn t look specifically for them. As for what to do that depends on whatt effect does that tumor have. Pituitary gland produces many hormones so now lab test for hormonal levels is necessary. Afterwards depending on hormonal level alterations and whether the tumor causes any compression to surrounding structures a decision will be made whether to consider surgery or follow up and medication. I remain at your disposal for other questions.