The impact of recent advances in diagnostic technology on the clinical presentation of phaeochromocytoma

Phaeochromocytomas discovered during coronial autopsies in Sydney, Melbourne and Auckland

BACKGROUND

The diagnosis of phaeochromocytoma can be difficult and previous autopsy studies have found that many of these tumours are not recognised during life.

AIM

To determine the incidence of phaeochromocytoma during coronial autopsies and the characteristics of the individuals concerned.

METHOD

Review of coronial autopsy records from Auckland (1981-97), Melbourne (1991-97) and Sydney (1991-97).

RESULTS

Twenty-two patients were found giving an incidence of 0.05% (one tumour per 2031 autopsies) with similar figures in each centre. Thirteen of the patients were men, 12 were overweight (body mass index >25 kg/m2) and three of the seven Auckland patients were Maori. Fourteen of the tumours were left-sided, one was extra-adrenal and none had metastasised. The one patient with bilateral tumours had multiple endocrine neoplasia syndrome type 2 (MEN-2) which had not been recognised during life. The heart weight was increased in 95% of the patients. The tumour may have contributed to the patient's death in up to 50% of the cases, although the true significance of these lesions as a cause of death remains unclear. Three patients died soon after general anaesthetics had been given for unrelated reasons.

CONCLUSIONS

Even though phaeochromocytomas are uncommon, we fail to diagnose a significant number of these tumours during life. Methods are needed to increase the detection of phaeochromocytoma and to distinguish functional and non-functional tumours.

REPCAT: Desktop expert system for interpreting and validating laboratory data for pheochromocytoma diagnosis with the database application Omnis 7™

To aid in the validation and interpretive reporting of results from multianalyte diagnostic testing for pheochromocytoma (PHEO), we have developed a desktop personal computer-based laboratory expert system (REPCAT). REPCAT utilizes a commercial database application to run procedures that assess analytical and clinical data relating to patient urine or plasma samples. REPCAT was used to evaluate the raw data from >4000 24-h urine samples submitted to our laboratory for testing for the presence of PHEO. REPCAT performed equivalently to an expert pathologist in assessing the presence and class of PHEO (epinephrine, norepinephrine, or mixed secretor). No false negatives were generated and it assigned a correct interpretation (on the basis of subsequent clinical and biochemical investigation) for each of the primary diagnostic samples from these patients.

Laboratory diagnosis of phaeochromocytoma: which analytes should we measure?

There is a diversity of advice in the literature as to which biochemical assays are best suited to the investigation of patients with a suspected phaeochromocytoma. The challenge for the clinical laboratory is to select those assays which detect all phaeochromocytomas, whilst having the lowest incidence of false positive diagnoses. We compared the sensitivity and specificity of a wide range of assays currently used for the biochemical diagnosis of phaeochromocytoma using either specific gas chromatographic-mass spectrometric (GC/MS) or high performance liquid chromatography-electrochemical detection (HPLC/ED) techniques. Noradrenaline (NA), adrenaline (ADR), dopamine (DA), 3,4-dihydroxyphenylglycol (DHPG), hydroxymethoxymandelic acid (HMMA), normetanephrine (NMET) and metanephrine (MET) were measured in 24 h urine specimens from 20 patients with histologically proven phaeochromocytoma and a large group of patients referred for investigation but subsequently found not to have a phaeochromocytoma. Because phaeochromocytomas are a heterogeneous group of hormone secreting tumours, no single analyte could achieve 100% sensitivity; 100% sensitivity was achieved only when the combination of both NA and ADR or NMET and MET was used. DA, DHPG and HMMA all had poor sensitivities. HMMA had a sensitivity of 70% when using the upper 95% confidence level (48 mumol/24 h) of the non-tumour patients as the cut-off. By lowering the cut-off to 35 mumol/24 h the sensitivity could be increased to 100% but at the expense of the specificity which was decreased from 98 to 92%. On the basis of this study we recommend the specific measurement of either NA and ADR or NMET and MET as the most suitable analytes for the detection of phaeochromocytoma, and further that, due to its poor specificity, HMMA be abandoned as a suitable analyte.