Unusual synchronous skeletal muscle and lung metastasis in papillary thyroid cancer: A case report and review of the literature

Abstract

Papillary thyroid cancer (PTC) frequently metastasizes to the cervical lymph region and less often to the lung and bone. Metastasis to the skeletal muscles from PTC is extremely rare, especially concurrent lung and skeletal muscle metastases. The present study reports the case of a 31-year-old man with synchronous metastasis to the skeletal muscle and lung from PTC, six years following total thyroidectomy and consecutive ¹³¹Iodine treatments. Magnetic resonance imaging (MRI) revealed a 1.7×1.2×1.5 cm mass in the left gastrocnemius muscle, indicating a neurogenic tumor. The mass was subsequently resected and confirmed via histopathology to be metastatic PTC. We propose that, in the follow-up of patients with PTC, the measurable serum thyroglobulin level, whole body scan and other imaging modalities including MRI or positron emission tomography/computed tomography, must be closely monitored for potential distant metastases, particularly in cases of PTC with aggressive pathological behavior.

Keywords: lung metastasis; papillary thyroid cancer; skeletal muscle metastasis.

Figure 1

(A) ¹³¹Iodine whole-body scan, seven days after an oral therapeutic dose of 3700 MBq ¹³¹Iodine in 2007, showed a diffuse uptake in the chest and focus of the neck. (B) Computed tomography scan of the thorax showed extensive metastatic disease of the lungs. (C) Magnetic resonance imaging showed gastrocnemius muscle metastasis in the left leg.

Figure 2

(A) Doppler ultrasound revealed a hypoechoic lesion with peripheral hypervascularity. (B) Infiltrating clusters of papillary tumor cells in the skeletal muscle (HE staining; magnification, ×50). (C) Typical nuclear inclusions and grooves (HE staining; magnification, ×200). (D) Immunohistochemistry showed tumor cells positive for thyroid transcription factor 1. HE, hematoxylin and eosin.