Probability of malignancy in solitary pulmonary nodules using fluorine-18-FDG and PET

Nearly one-third of solitary pulmonary nodules are radiographically indeterminate for the presence of malignancy.

METHODS

FDG-PET imaging was used to differentiate benign and malignant solitary pulmonary nodules in 61 patients with radiographically indeterminate nodules. After confirmation of the histological diagnosis, the probability for cancer was established for positive and negative PET scans and compared to the risk estimates calculated using other patient variables.

RESULTS

FDG-PET had a sensitivity, specificity and positive predictive value of 93%, 88% and 92%, respectively, for detecting malignancy in indeterminate solitary pulmonary nodules. The probability of malignancy with a positive PET scan is 83%, which increases with the patient's age (90% in >60 yr) and the size of the nodule. A negative PET scan is associated with only a 4.7% risk of malignancy. FDG-PET also accurately characterized hilar/mediastinal lymphadenopathy in 12 patients with associated lymph node lesions.

CONCLUSION

FDG-PET imaging can be a useful noninvasive test to determine the risk estimate or probability of cancer as well as preoperative staging in patients with radiographically indeterminate solitary pulmonary nodules.

Subunit folding and alpha delta heterodimer formation in the assembly of the nicotinic acetylcholine receptor. Comparison of the mouse and human alpha subunits

We have used the mouse alpha (alpha M) and human alpha (alpha H) subunits to investigate the molecular mechanisms of assembly of the mammalian acetylcholine receptor (AChR) transiently expressed in COS cells. COS cells expressing hybrid receptors incorporating alpha H along with other mouse subunits exhibited a 2-fold higher level of surface alpha-bungarotoxin (BuTx) binding than cells expressing the wild-type mouse AChR. When expressed either alone or with the delta subunit in COS cells, alpha H acquired the BuTx binding conformation (alpha Tx) more efficiently than did alpha M. By oligonucleotide-directed mutagenesis we showed that 2 residues in the amino-terminal domain were responsible for the differences between alpha M and alpha H. Alpha MST, the modified mouse alpha subunit, both folded more efficiently to form alpha Tx and was more effective in forming a stable alpha delta heterodimer than was alpha M. The kinetics of alpha Tx and alpha delta heterodimer formation revealed that the delta subunit increased the conversion of immature forms of the alpha subunit into the BuTx binding form and therefore provides evidence for interaction between the delta subunit and the immature form of the alpha subunit. These results provide evidence of the importance of the amino-terminal domains of the AChR subunits in the assembly process.