Should I go through with a malpractice Lawyer? What are my chances for winning?

So a year ago I went to a specialist to have a lump on my neck checked out. I specifically asked for a biopsy because the DR. was concerned about it being lymphoma. He examined the lump and determined that it was a cyst. I then asked to do the biopsy for clarity and he refused because his professional opion was more accurate and reassured me it was not Lymphoma. Now a year later, more symptoms led me to another DR. where they immediately knew it was not a cyst and test results confirm the fact that it is Lymphoma. Seems to be pretty black and white but I need some advice before finding the right lawer. Thanks!