PNA Medical Corner: Diagnosing Tumor Types
This month’s PNA Medical Corner features an article co-written by two members of the PNA: Dr. Garni Barkhoudarian, who is a member of the PNA Board of Directors; and Dr. Ed Laws, a member of the PNA Scientific Advisory Board. The paper looks at the best way to diagnose a prolactinoma versus an NFA (non-functioning adenoma) before surgery. It concludes that the volume of prolactin-producing tissue is more important than the volume of the non-functioning adenoma and volume should be a determining factor to diagnose the tumor as a prolactinoma or an NFA.
Burke WT1, Penn DL2, Castlen JP1, Donoho DA2, Repetti CS2, Iuliano S2, Barkhoudarian G3, Laws ER2.
J Neurosurg. 2019 Jun 14:1-8. doi: 10.3171/2019.3.JNS19121. [Epub ahead of print]
1University of Louisville School of Medicine, University of Louisville, Louisville, Kentucky.
2Department of Neurosurgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts; and.
3Pacific Neuroscience Institute at the John Wayne Cancer Institute, Santa Monica, California.
Prolactinoma and nonfunctioning adenoma (NFA) are the most common sellar pathologies, and both can present with hyperprolactinemia. There are no definitive studies analyzing the relationship between the sizes of prolactinomas and NFAs and the serum prolactin level. Current guidelines for serum prolactin level cutoffs to distinguish between pathologies are suboptimal because they fail to consider the adenoma volume. In this study, the authors attempted to describe the relationship between serum prolactin level and prolactinoma volume. They also examined the predictive value that can be gained by considering tumor volume in differentiating prolactinoma from NFA and provide cutoff values based on a large sample of patients.
A retrospective analysis of consecutive patients with prolactinomas (n = 76) and NFAs (n = 217) was performed. Patients were divided into groups based on adenoma volume, and the two pathologies were compared.
A strong correlation was found between prolactinoma volume and serum prolactin level (r = 0.831, p < 0.001). However, there was no significant correlation between NFA volume and serum prolactin level (r = -0.020, p = 0.773). Receiver operating characteristic curve analysis of three different adenoma volume groups was performed and resulted in different serum prolactin level cutoffs for each group. For group 1 (≤ 0.5 cm3), the most accurate cutoff was 43.65 μg/L (area under the curve [AUC] = 0.951); for group 2 (> 0.5 to 4 cm3), 60.05 μg/L (AUC = 0.949); and for group 3 (> 4 cm3), 248.15 μg/L (AUC = 1.0).
Prolactinoma volume has a significant impact on serum prolactin level, whereas NFA volume does not. This finding indicates that the amount of prolactin-producing tissue is a more important factor regarding serum prolactin level than absolute adenoma volume. Hence, volume should be a determining factor to distinguish between prolactinoma and NFA prior to surgery. Current serum prolactin threshold level guidelines are suboptimal and cannot be generalized across all adenoma volumes.
AUC = area under the curve; HPT = highest pretreatment; NFA = nonfunctioning adenoma; ROC = receiver operating characteristic; TSS = transsphenoidal surgery; nonfunctioning adenoma; pituitary adenoma; pituitary surgery; prolactinoma; transsphenoidal surgery