The final diagnosis of pheochromocytoma is based on three critical pieces of evidence: 1) elevated biochemical markers for pheochromocytoma, 2) an adrenal tumor, and 3) agreement between the extent of marker elevation and the imaging characteristics of the tumor. I have discussed 1) and 2) in previous posts, I will focus on 3) in this one.
What I mean for "agreement" is that the tumor size and the levels of markers should be roughly matching because larger tumors tend to have higher marker levels. For example, if a patient has plasma normetanephrine levels 20 fold elevated and has a 2-cm left adrenal tumor, the small adrenal tumor is not the pheochromocytoma that produces such high levels of plasma normetanephrine. There should be another tumor somewhere in the body. Another example. If a patient has plasma normetanephrine levels 1.5 fold elevated but has a left adrenal tumor measuring 5.5 cm, this left adrenal tumor is probably not a pheochromocytoma. I cannot give a very quantitative rule about marker levels and tumor size because there are no such rules. A doctor's experience is key here. The good news is that most tumors do have agreement between marker levels and tumor size on the first imaging study.
Dr. Pheo
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Perhaps you might say a few more words of guidance with respect to diagnostic scans. This once again is based on my own experience and "mistakes" that could have been avoided. In many respects it will not be an issue if the potential pheo-ite takes themselves off to a recognised center of expertise on pheos to verify and complete the diagnosis, but I think that many might find themselves getting the wrong or incomplete diagnosis. Let me explain.
ReplyDeleteI was correctly diagnosed with a reoccurrence of a pheo based on 24U & ultrasound but it was missed that it might be metastatic. I had a MIBG diagnostic scan but this was poorly done on old equipment with no combined CT scan. Further the isotope 131I was used with the result that it was a noisy scan clearly showing the pheo in the adrenal region (we had found the dropped coin under the streetlight!). The decision was made to surgically remove the pheo+kidney that had been invaded. The problem with this story was there was at least another pheo lurking elsewhere hidden in the noise of the MIBG scan. It was only when my biomarkers didn’t come down appreciably after the surgery that I took myself off to a center of competence. A low noise 123I-MIBG SPECT scan with combined CT clearly showed the missed pheos: it was metastatic pheo. Had I gone directly to a center of competence I think I would have received a correct early diagnosis and the treatment might have been different. (I went back and carefully inspected the noisy 131I-MIBG and could discern just above the noise signals that had been “overlooked”). This is a too lengthy story but my point is “beware of being sent to an outdated scanner associated with the group practice” or putting it more positively “ensure the radiologist is experienced in scanning for pheos and interpreting the images”. One last point “with pheos do not believe a pathology report of benign”.
Thank you for sharing your experience. Your point of seeking care in a center with expertise is extremely important. I will write more about scans soon.
ReplyDeleteDr. Pheo
Hi Dr Pheo,
ReplyDeleteI'm interested in your input please. I just had the results for a 24hr Urine after a ~1.1cm adrenal incidentaloma was found during CT scan for something else. My epinephrine was only slightly raised at 191nmoL (ref <190), but the metanephrine was 960nmoL (ref <350). Also the norepinephrine was normal, but the normetanephrine was a bit high at 864nmoL (ref <650). I think other parameters were normal. I suppose I'm just looking for reasons for this to be a false positive, but actually from reading your comments, it could be highly consistent with a 1.1cm pheo couldn't it? I have had some weird symptoms for a while that I've been dismissing... it is all adding up now. I'm a 42 yr old female. Thanks.
Dear Annie,
DeleteSorry for the late response. The probability of pheo is pretty high. The imaging characteristics of this tumor will also help making the diagnosis.
Dr. Pheo