Improved discrimination of melanotic schwannoma from melanocytic lesions by combined morphological and GNAQ mutational analysis

The histological differential diagnosis between melanotic schwannoma, primary leptomeningeal melanocytic lesions and cellular blue nevus can be challenging. Correct diagnosis of melanotic schwannoma is important to select patients who need clinical evaluation for possible association with Carney complex. Recently, we described the presence of activating codon 209 mutations in the GNAQ gene in primary leptomeningeal melanocytic lesions. Identical codon 209 mutations have been described in blue nevi. The aims of the present study were to (1) perform a histological review of a series of lesions (initially) diagnosed as melanotic schwannoma and analyze them for GNAQ mutations, and (2) test the diagnostic value of GNAQ mutational analysis in the differential diagnosis with leptomeningeal melanocytic lesions. We retrieved 25 cases that were initially diagnosed as melanotic schwannoma. All cases were reviewed using established criteria and analyzed for GNAQ codon 209 mutations. After review, nine cases were classified as melanotic schwannoma. GNAQ mutations were absent in these nine cases. The remaining cases were reclassified as conventional schwannoma (n = 9), melanocytoma (n = 4), blue nevus (n = 1) and lesions that could not be classified with certainty as melanotic schwannoma or melanocytoma (n = 2). GNAQ codon 209 mutations were present in 3/4 melanocytomas and the blue nevus. Including results from our previous study in leptomeningeal melanocytic lesions, GNAQ mutations were highly specific (100%) for leptomeningeal melanocytic lesions compared to melanotic schwannoma (sensitivity 43%). We conclude that a detailed analysis of morphology combined with GNAQ mutational analysis can aid in the differential diagnosis of melanotic schwannoma with leptomeningeal melanocytic lesions

Activating mutations of the GNAQ gene: a frequent event in primary melanocytic neoplasms of the central nervous system

Primary melanocytic neoplasms of the central nervous system (CNS) are uncommon neoplasms derived from melanocytes that normally can be found in the leptomeninges. They cover a spectrum of malignancy grades ranging from low-grade melanocytomas to lesions of intermediate malignancy and overtly malignant melanomas. Characteristic genetic alterations in this group of neoplasms have not yet been identified. Using direct sequencing, we investigated 19 primary melanocytic lesions of the CNS (12 melanocytomas, 3 intermediate-grade melanocytomas, and 4 melanomas) for hotspot oncogenic mutations commonly found in melanocytic tumors of the skin (BRAF, NRAS, and HRAS genes) and uvea (GNAQ gene). Somatic mutations in the GNAQ gene at codon 209, resulting in constitutive activation of GNAQ, were detected in 7/19 (37%) tumors, including 6/12 melanocytomas, 0/3 intermediate-grade melanocytomas, and 1/4 melanomas. These GNAQ-mutated tumors were predominantly located around the spinal cord (6/7). One melanoma carried a BRAF point mutation that is frequently found in cutaneous melanomas (c.1799 T>A, p.V600E), raising the question whether this is a metastatic rather than a primary tumor. No HRAS or NRAS mutations were detected. We conclude that somatic mutations in the GNAQ gene at codon 209 are a frequent event in primary melanocytic neoplasms of the CNS. This finding provides new insight in the pathogenesis of these lesions and suggests that GNAQ-dependent mitogen-activated kinase signaling is a promising therapeutic target in these tumors. The prognostic and predictive value of GNAQ mutations in primary melanocytic lesions of the CNS needs to be determined in future studies

Mutations in G Protein Encoding Genes and Chromosomal Alterations in Primary Leptomeningeal Melanocytic Neoplasms

Limited data is available on the genetic features of primary leptomeningeal melanocytic neoplasms (LMNs). Similarities with uveal melanoma were recently suggested as both entities harbor oncogenic mutations in GNAQ and GNA11. Whether primary LMNs share additional genetic alterations with uveal melanoma including copy number variations is unknown. Twenty primary LMNs ranging from benign and intermediate-grade melanocytomas to melanomas were tested by direct sequencing for hotspot mutations in the genes GNA11, GNAQ, BRAF, NRAS and HRAS. Furthermore, the lesions were tested for copy number variations of chromosomes frequently present in uveal melanoma (1p, 3, 6 and 8q) by multiplex ligation-dependent probe amplification (MLPA). Genome-wide analyses of copy number alterations of two leptomeningeal melanocytic neoplasms were performed using the OncoScan SNP-array. GNAQQ209 mutations were present in eleven LMNs, while two of 20 cases carried a GNA11Q209 mutation. No BRAF, HRAS or NRAS hotspot mutations were detected. Monosomy 3 and gain of 8q were present in one leptomeningeal melanoma, and one intermediate-grade melanocytoma harbored a gain of chromosome 6. With MLPA, the melanocytomas did not show any further gross chromosomal variations. Our data shows that primary LMNs, like uveal melanoma, harbor oncogenic mutations in GNAQ and GNA11 but lack mutations in BRAF, NRAS and HRAS. This finding may help in the differential diagnosis between a primary LMN and a metastasis from a cutaneous melanoma to the central nervous system. Copy number variations in some aggressive LMNs resemble those present in uveal melanoma but their prognostic significance is unclear

89Zr-DFO-Durvalumab PET/CT Before Durvalumab Treatment in Patients with Recurrent or Metastatic Head and Neck Cancer

In this PD-L1 ImagiNg to prediCt durvalumab treatment response in SCCHN (PINCH) study, we performed 89Zr-DFO-durvalumab (anti-PD-L1 [programmed death ligand 1]) PET/CT in patients with recurrent or metastatic (R/M) squamous cell carcinoma of the head and neck (SCCHN) before monotherapy durvalumab treatment. The primary aims were to assess safety and feasibility of 89Zr-DFO-durvalumab PET imaging and predict disease control rate during durvalumab treatment. Secondary aims were to correlate 89Zr-DFO-durvalumab uptake to tumor PD-L1 expression, 18F-FDG uptake, and treatment response of individual lesions. Methods: In this prospective multicenter phase I-II study (NCT03829007), patients with incurable R/M SCCHN underwent baseline 18F-FDG PET and CT or MRI. Subsequently, PD-L1 PET imaging was performed 5 d after administration of 37 MBq of 89Zr-DFO-durvalumab. To optimize imaging conditions, dose finding was performed in the first 14 patients. For all patients (n = 33), durvalumab treatment (1,500 mg/4 wk, intravenously) was started within 1 wk after PD-L1 PET imaging and continued until disease progression or unacceptable toxicity (maximum, 24 mo). CT evaluation was assessed according to RECIST 1.1 every 8 wk. PD-L1 expression was determined by combined positive score on (archival) tumor tissue. 89Zr-DFO-durvalumab uptake was measured in 18F-FDG-positive lesions, primary and secondary lymphoid organs, and blood pool. Results: In total, 33 patients with locoregional recurrent (n = 12) or metastatic SCCHN (n = 21) were enrolled. 89Zr-DFO-durvalumab injection was safe. A dose of 10 mg of durvalumab resulted in highest tumor-to-blood ratios. After a median follow-up of 12.6 mo, overall response rate was 26%. The disease control rate at 16 wk was 48%, with a mean duration of 7.8 mo (range, 1.7-21.1). On a patient level, 89Zr-DFO-durvalumab SUVpeak or tumor-to-blood ratio could not predict treatment response (hazard ratio, 1.5 [95% CI, 0.5-3.9; P = 0.45] and 1.3 [95% CI, 0.5-3.3; P = 0.60], respectively). Also, on a lesion level, 89Zr-DFO-durvalumab SUVpeak showed no substantial correlation to treatment response (Spearman ρ, 0.45; P = 0.051). Lesional 89Zr-DFO-durvalumab uptake did not correlate to PD-L1 combined positive score but did correlate to 18F-FDG SUVpeak (Spearman ρ, 0.391; P = 0.005). Conclusion: PINCH is the first, to our knowledge, PD-L1 PET/CT study in patients with R/M SCCHN and has shown the feasibility and safety of 89Zr-DFO-durvalumab PET/CT in a multicenter trial. 89Zr-DFO-durvalumab uptake did not correlate to durvalumab treatment response