Hereditary pheochromocytoma/paraganglioma syndrome with a novel mutation in the succinate dehydrogenase subunit B gene in a Japanese family: two case reports

Case report: Intraoperative frozen section analysis of Thyroid paraganglioma

Paraganglioma (PGL) is a neuroendocrine tumor that arises from the sympathetic or parasympathetic paraganglia. Primary thyroid PGL is extremely rare. PGL may be difficult to diagnose on frozen sections because its histopathological features, such as polygonal tumor cells with eosinophilic cytoplasm arranged irregularly, overlap with those of thyroid follicular adenoma. We present a case of thyroid PGL in a female patient and provide a detailed description of the patient's clinicopathologic characteristics. Cervical computed tomography showed a left thyroid mass with uneven density. Intraoperative frozen section analysis showed an uneven fibrous septa and rich networks of delicate vessels surrounding tumor cell nests. The tumor cells were polygonal or epithelioid with eosinophilic cytoplasm, arranged in a nest, trabecular, or organoid pattern were and diagnosed as thyroid follicular adenoma. However, in postoperative immunohistochemistry, these were diagnosed as thyroid PGL. The postoperative recovery was uneventful. The patient showed no signs of tumor recurrence or metastasis until 16 months of follow-up. Herein, we summarize the characteristic features of thyroid PGL based on frozen section analysis. In the appropriate clinical context, its proper use as diagnostic and differential diagnostic management strategies is recommended.

Prevalence of Germline Variants in a Large Cohort of Japanese Patients with Pheochromocytoma and/or Paraganglioma

Simple Summary

Pheochromocytoma/paraganglioma (PPGL) has been recognised as one of the most frequent inherited tumours with genetic heterogeneity based on studies in Caucasian populations. Early identification of germline variants is crucial for accurate treatment and follow-up in affected patients and relatives. However, there are only a few large cohort studies in Asia and none from the Japanese population. In this first comprehensive study of Japanese patients with PPGL, we found one in four PPGLs with apparently sporadic presentation harboured germline variant in any of the seven susceptibility genes (MAX, SDHB, SDHC, SDHD, TMEM127, VHL, and RET). SDHB was the most frequently mutated gene and was strongly associated with metastatic PPGLs. Our findings emphasise the importance of genetic testing in determining appropriate treatment and follow-up strategies for patients and relatives.

Abstract

The high incidence of germline variants in pheochromocytoma and paraganglioma (PPGL) has been reported mainly in Europe, but not among Japanese populations in Asia. We aimed to study the prevalence of germline variants in Japanese PPGL patients and the genotype–phenotype correlation. We examined 370 PPGL probands, including 43 patients with family history and/or syndromic presentation and 327 patients with apparently sporadic (AS) presentation. Clinical data and blood samples were collected, and the seven major susceptibility genes (MAX, SDHB, SDHC, SDHD, TMEM127, VHL, and RET) were tested using Sanger sequencing. Overall, 120/370 (32.4%) patients had pathogenic or likely pathogenic variants, with 81/327 (24.8%) in AS presentation. SDHB was the most frequently mutated gene (57, 15.4%), followed by SDHD (27, 7.3%), and VHL (18, 4.9%). The incidence of metastatic PPGL was high in SDHB carriers (21/57, 36.8%). A few unique recurrent variants (SDHB c.137G>A and SDHB c.470delT) were detected in this Japanese cohort, highlighting ethnic differences. In summary, almost a quarter of patients with apparently sporadic PPGL in Japan harboured germline variants of the targeted genes. This study reinforces the recommendation in Western guidelines to perform genetic testing for PPGL and genotype-based clinical decision-making in the Japanese population.