Absence of the BRAF V600E mutation in pheochromocytoma

Composite pheochromocytoma/paraganglioma-ganglioneuroma: analysis of SDH and ATRX status, and identification of frequent HRAS and BRAF mutations

INTRODUCTION

Composite pheochromocytoma/paraganglioma (CP) is a rare neoplasm with most cases presented as single reports. Little is known about its pathogenesis and relationship with ordinary pheochromocytoma (PCC) or paraganglioma (PGL). Our study is aimed at analyzing the status of SDH and ATRX and identifying novel genetic changes in CP.

METHODS

Eighteen CP cases were collected. SDH and ATRX status was screened by immunohistochemistry. Targeted region sequencing (TRS) was successfully performed on formalin-fixed paraffin-embedded tissues in two cases within 3 years. Based on the TRS result, Sanger sequencing of BRAF and HRAS was performed in fifteen cases (including the two cases with TRS performed), with three cases excluded due to the limited amount of tissue.

RESULTS

Histopathologically, all the cases were composite PCC/PGL-ganglioneuroma (GN). The GN components were either closely admixed or juxtaposed with the PCC/PGL components, with a highly variable percentage (10-80%). All cases stained positive for SDHB and ATRX. HRAS and BRAF mutations were identified during TRS. In the subsequent Sanger sequencing, 20.0% (3/15) harbored BRAF mutations (K601E and K601N) and 46.7% (7/15) harbored HRAS mutations (Q61R, Q61L, G13R). The mutation rates were both significantly higher than reported in ordinary PCC/PGL.

CONCLUSIONS

We demonstrated that composite PCC/PGL-GN might be a unique entity with frequent HRAS and BRAF mutations rather than genetic changes of SDH and ATRX. Our findings revealed the possible pathogenesis of composite PCC/PGL-GN and provided clues for potential treatment targets.

Combined BRAFV600E analysis and 99mTc-MIBI scintigraphy can be a useful diagnostic tool in differentiated thyroid cancer patients with incomplete bio-chemical response to first radioiodine therapy (RAIT): a pilot investigation

PURPOSE

The aim of the present study was to evaluate the possible diagnostic role of the combined performance of BRAF mutation analysis and MIBI scintigraphy in papillary thyroid cancer (PTC) patients with incomplete bio-chemical response to first radioiodine therapy (RAIT) performed for thyroid remnant ablation.

METHODS

The records of 15 PTC patients with bio-chemical incomplete response to first RAIT were retrospectively analyzed. BRAF^V600E analysis on primary tumor samples was obtained in all cases along with neck ultrasonography and ^99mTc-MIBI scintigraphy of the neck-thorax regions at first follow-up. All patients then underwent RAIT with high radioiodine activities. A post-therapy whole-body scan (pT-WBS) was acquired 5-7 days after RAIT.

RESULTS

Abnormal radioiodine uptake was found in 10 out of the 15 patients (67%, ¹³¹I+ve), while in the remaining 33%, no abnormal radioiodine uptake was detected (5/15, ¹³¹I-ve). Abnormal tracer uptake was found in 6 out of 10 ¹³¹I+ve patients at ^99mTc-MIBI scintigraphy (MIBI+ve). BRAF^V600E mutation was not found in the majority of ¹³¹I+ve patients (9 out of 10 BRAF^V600E-ve). On the contrary, in the 5 ¹³¹I-ve patients, ^99mTc-MIBI scintigraphy did not show any abnormal tracer uptake (MIBI-ve), while BRAF^V600E mutation was present (BRAF^V600E+ve). Thus, in our series, the association between MIBI-ve scintigraphy and BRAF+ve mutation was a useful diagnostic tool in predicting negative pT-WBS outcome.

CONCLUSION

Albeit obtained in a small retrospective series, our results suggest that the combination of BRAF^V600E+ve mutation and MIBI-ve scintigraphy may be considered a negative prognostic clue, which predicts the absence of radioiodine uptake at pT-WBS in DTC patients with incomplete bio-chemical response to first RAIT.