PMC5222898_01
Histopathology of the primary gastric tumor. a Hematoxylin and eosin stain; original magnification x100. Atypical cells with cytoplasmic mucin are diffusely invading the gastric mucosa. b Hematoxylin and eosin stain; original magnification x400. Round-shaped cells with cytoplasmic mucin vacuoles and eccentrically placed nuclei are components of signet-ring-cell carcinoma (rectangle). Cells with a high nuclear-to-cytoplasmic ratio are components of poorly differentiated adenocarcinoma (oval)
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Fig1
The tumor found in the greater curvature of the middle body in the stomach was biopsied and diagnosed as adenocarcinoma (signet-ring-cell carcinoma/poorly differentiated adenocarcinoma; Fig. 1).
a Coronal maximum intensity projection (MIP) of 18F-FDG PET imaging before admission. Accumulation was found in the stomach, in the right hepatic lobe, in the extensive lymph node metastases, and in the whole thyroid gland. b Transverse section of the thyroid on 18F-FDG PET/CT imaging before admission. Diffuse uptake in bilateral thyroid lobes was observed. c Transverse section of the thyroid on CT imaging after admission. The thyroid gland was diffusely swollen. Its size enlarged and its CT value decreased after hospitalization. In addition, the adipose tissue concentration in the surrounding area increased
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Fig2
On 2-deoxy-2-(18F) fluoro-d-glucose positron emission tomography/computed tomography imaging (PET/CT), accumulation was detected in the entire stomach; in the portal and posterior area of the right hepatic lobe; in the cervical, left supraclavicular, left axillary, left parasternal, and superior mediastinal lymph nodes (which suggested extensive lymph node metastases); and interestingly and unexpectedly, in the thyroid, where 18F-FDG was diffusely taken up in both lobes, for some unknown reason (Fig. 2a, b). As for the thyroid, both the lobes were diffusely enlarged and exhibited low density on CT (Fig. 2c).
Thyroid ultrasonography after admission. a Transverse section of the thyroid gland on B-mode (brightness mode) ultrasound imaging. The thyroid was diffusely enlarged, with a 10-mm-thick isthmus. No nodular lesion was observed. The thyroid parenchyma was not of uniform echogenicity, with many hypoechoic reticular lines scattered in it. b Longitudinal section of the right lobe of the thyroid on color Doppler ultrasound imaging. c Longitudinal section of the left lobe of the thyroid on color Doppler ultrasound imaging. A Doppler signal was not detected in the hypoechoic reticular lines
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Fig3
Cytology specimen that was obtained by fine-needle aspiration from the right lobe of the thyroid gland (Papanicolaou stain; original magnification x400). Discohesive atypical cells with irregular hyperchromatic nuclei containing prominent nucleoli were present. Round-shaped cells with cytoplasmic mucin vacuoles and eccentrically placed nuclei were signet-ring-cell carcinoma cells (arrow). Cells with a high nuclear-to-cytoplasmic ratio were thought to be poorly differentiated adenocarcinoma cells (arrowhead). There were numerous mitotic figures (big arrowhead). Based on these findings, the thyroid lesion was defined as "malignant" (metastatic carcinoma) by TBSRTC
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Fig4
These findings indicated that the thyroid lesion was categorized as "malignant" (metastatic carcinoma) according to the Bethesda system for reporting thyroid cytopathology (TBSRTC), and were consistent with the metastasis of the gastric signet-ring-cell carcinoma/poorly differentiated adenocarcinoma to the thyroid gland (Fig. 4).