Concurrent BRAF V600E mutated papillary thyroid carcinoma and Erdheim–Chester disease

Excerpt

A 66-year-old man was referred to our Department for ¹³¹I therapy after surgery for a papillary thyroid carcinoma (PTC). He had a history of dysarthria since 2014. Brain magnetic resonance (MR) imaging revealed diffuse spots of hyperintense signal in infratentorial sites and slight thickening of the pituitary pedunculus. In September 2017, he underwent bilateral ureteral stenting for stasis. After 2 months, an abdominal computed tomography (CT) scan with contrast media then showed a perinephric infiltrating tissue (Fig. 1a), a retroperitoneal lesion (29 × 19 mm), and a sclerotic iliac bone lesion. In December 2017, a perinephric biopsy and the laparoscopic removal of the retroperitoneal lesion revealed a Castleman-like lymphadenitis with typical histiocytes and with a somatic BRAF V600E mutation, leading to the diagnosis of Erdheim–Chester disease (ECD) [1]. As part of the ECD workup, a thyroid ultrasound showed two hypoechogenic nodules with microcalcifications of 7 and 14 mm, respectively, and suspicious central compartment lymph nodes. Fine needle cytology was consistent with the diagnosis of PTC. In July 2018, a total thyroidectomy with a central neck dissection confirmed a bilateral follicular variant of papillary carcinoma with three lymph node metastases, classified as T1bmN1aM0, according to the 2017 TNM classification. A somatic BRAF V600E mutation was found in both thyroid tumors. After 6 weeks of neck surgery, the patient underwent ¹³¹I therapy with 1850 MBq with only thyroid bed uptake on the whole-body scan. The thyroid cancer follow-up visit on l-thyroxine therapy at 6 months was normal. In December 2018, a targeted therapy of ECD with a BRAF inhibitor (vemurafenib, 480 mg twice a day) [2] was initiated and the 3 months control with ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET)/CT scan did not show any abnormal finding (Fig. 1b).

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