case_images: PMC11150598_01
case_images: Initial ultrasound and SPECT/CT. Ultrasound on axial (A) and sagittal (B) views showed a well delineated hypoechoic round lesion adjacent to the inferior left thyroid lobe and left common carotid artery. On 99mTc-sestamibi SPECT/CT, avid uptake was demonstrated on axial (C) and coronal (D) planes, which was initially thought to be consistent with a parathyroid adenoma.
case_images: fendo-15-1258233-g001.jpg
case_images: PMC11150598_01_fendo-15-1258233-g001.jpg
case_images: f1
case_images: A new ultrasound was performed in January 2019, showing a 2.6 cm hypoechoic mass (4.5 ml in estimated volume) located posterior to the inferior pole of the left thyroid lobe, with scant vascularity ( Figures 1A, B ). A SPECT/CT was thus performed in January 2019, showing 99mTc-sestamibi avidity only in the larger nodule, which was negative for pertechnetate ( Figures 1C, D ).
case_images: Follow-up CT and MRI. On axial (A) and coronal (B) contrast-CT views, the lesion again appeared well delineated with moderate enhancement and only a slight mass effect on the inferior aspect of the left thyroid lobe, on the left common carotid artery (CCA) and trachea. Perilesional fat was normal, and no dysplastic vessel was seen within the tumor. Axial T2-weighted MR images (C) highlighted that a thin hypointense rim (arrows) in continuity with the esophageal external layer wrapped the lesion. Homogeneous moderate enhancement was also seen on post-contrast coronal fat saturated T1-weighted images (D). 7-month follow-up MRI demonstrated slow growth of the mass, which increased the lateral shift of the left CCA and the medial shift of the trachea without any sign of invasion.
case_images: fendo-15-1258233-g002.jpg
case_images: PMC11150598_01_fendo-15-1258233-g002.jpg
case_images: f2
case_images: Further revision of all images available from the past 3 years showed that the mass had clearly grown, with an estimated volume doubling time of approximately 1 year (352 days) ( Figure 2 ). The next MRI was performed about 7 months later, showing a further increase in volume ( Figure 2 ).
case_images: Surgical field by left cervicotomy approach. The greyish mass is well exposed in the center of the field (A) framed by the common carotid artery (CCA) inferiorly and the left recurrent laryngeal nerve (RLN) passing superficially. After enucleation (B) all structures seems intact except for the esophagus's adventitia and muscularis propria layers. During esophageal insufflation, no perforation was visualized (C). Labels:   left RLN, Delta CCA,  internal jugular vein,   inferior left parathyroid, * esophagus submucosal layer, # omo-hyoidien muscle, X thyroid left lobe.
case_images: fendo-15-1258233-g003.jpg
case_images: PMC11150598_01_fendo-15-1258233-g003.jpg
case_images: f3
case_images: The RLN was carefully dissected from the capsule of the schwannoma without effraction ( Figure 3A ). Ultimately, the schwannoma was detached from the submucosal layer of the esophagus ( Figures 3B, C ,  Figure 4A ). Mucosal perforation was ruled-out by the absence of air leak while insufflating the esophagus through a naso-oesophageal tube with a pressure of 30 cm H2O ( Figure 3C ). The left inferior parathyroid gland was also preserved with its vascularization during the dissection ( Figure 3B ).
case_images: Histological analysis of the specimen. The specimen is shown after enucleation, without effraction of the mass (A). Histological examination showed a proliferation of spindle-shaped cells with eosinophilic ill-defined cytoplasm and irregular, elongated nuclei without mitosis or necrosis (B), hematoxylin-eosin stain). Tumor cells were strongly positive for S100 (C).
case_images: fendo-15-1258233-g004.jpg
case_images: PMC11150598_01_fendo-15-1258233-g004.jpg
case_images: f4
case_images: Ultimately, the schwannoma was detached from the submucosal layer of the esophagus ( Figures 3B, C ,  Figure 4A ). The Ki67 proliferative index was 5% ( Figures 4B, C ).