Is the lump under my arm likely to be some form of cancer?

I found a lump under my left arm 3 weeks ago, it was painless and small so I never thought anything about it until this past week when it was MUCH larger. It now can be seen buldging out of the arm pit. I went into a doctor and he says it is less likely to be breast cancer due to my age, 31, but ordered an ultrasound of the auxilary arm pit. The breast exam he did checked out clean, no lumps. What is the chance this lump being some form of cancer? I have other symptoms along with the lump. I have extreme itching all over my body that comes and goes, my hair falls out (more like a major thinning, not clumps, but a handful with each shower) has been for a few years now. I've had two children ages 8 and 2. Breast cancer doesn't run in my family but other cancers are very thick in my family tree. Should I be worried about cancer, if so what kinds, and what can be done about them? How likely is this to turn out to be hodgkins?

[japdip]

Since your testing so far has been negative I doubt that this could be connected to breast cancer. You might consider some additional testing however to determine the cause of this enlarged node. Eventually a biopsy of the node may be necessary. I would suggest that you keep looking until you have some definite diagnosis. Regards ....

[StormingRachie]

Thank you for taking time to read and get back with me. I do plan on looking until I get a definite diagnosis. I am wondering what can an ultrasound really tell the doctor? It won't tell him whether it is cancer right? What would be the next step after an ultrasound of under arm area?

[japdip]

No, an Ultrasound cannot distinguish between cancer and benign BUT it may give an indication as to something being more or less likely to be a specifcic finding. A biopsy is the ONLY method for diagnosis and that may be the next step.  Regards ....