Skeletal Muscle Metastasis as an Initial Presentation of Follicular Thyroid Carcinoma: A Case Report and a Review of the Literature

Abstract

Introduction. Follicular thyroid carcinoma (FTC) frequently metastasizes to the lungs and bones. However, metastasis to the skeletal muscles is an extremely rare manifestation of FTC. To date, only seven cases of FTC have been reported in the literature. Skeletal muscle metastases from FTC usually remain asymptomatic or manifest as swelling and are associated with dismal prognosis. Case Presentation. A 45-year-old Saudi woman presented with right buttock swelling since 8 months. Physical examination revealed right gluteal mass of size 13 × 10 cm and right thyroid lobe nodule. The rest of examination was unremarkable. Magnetic resonance imaging (MRI) showed 13 × 11.7 × 6.8 cm lobulated mass arising from the gluteus medius muscle, and tru-cut biopsy confirmed the metastatic papillary carcinoma of thyroid origin. The patient subsequently underwent palliative radiotherapy followed by total thyroidectomy and radioactive iodine ablation. At the time of publication, the patient was alive with partial response in gluteal mass. Conclusion. Skeletal muscles metastases are a rare manifestation of FTC, and searching for the primary focus in a patient with skeletal muscle metastasis, thyroid cancer should be considered as differential diagnosis.

Skeletal muscle metastases from papillary and follicular thyroid carcinomas: An extensive review of the literature

“…In contrast to the results of Song et al ( 5 ), the present review identified that among the patients with muscle DTC metastasis with a detailed medical history, 1/3 complained of muscle pain, and the metastatic tumor could be detected by palpation in the majority of cases. This finding is in accordance with the statement by Tunio et al that ‘skeletal muscle metastases present as painful masses’ ( 11 ). However, it is difficult to agree with the statement by Xue et al that ‘Most of skeletal muscle metastases are silent and may occasionally present as painful masses’ ( 12 ).…”

“…However, it is difficult to agree with the statement by Xue et al that ‘Most of skeletal muscle metastases are silent and may occasionally present as painful masses’ ( 12 ). The mean size of the metastatic tumors was 6 cm, and this size is similar to that described by Tunio et al (2–12 cm) ( 11 ).…”

“…In 2013, Pirvu et al ( 10 ) presented a case of FTC pelvic muscle metastasis and reported just 5 cases of DTC skeletal muscle metastasis in the literature. Tunio et al ( 11 ) described the FTC synchronous metastatic infiltration of 4 muscles, identifying just 7 cases of FTC skeletal muscle metastasis in the literature; the authors presented these 7 cases in a table, including 3 cases of FTC and 4 cases of PTC ( sic ). In 2014, Xue et al ( 12 ) investigated synchronous thigh and buttock FTC metastases, and analyzed the existing literature; this group identified just 11 cases of DTC muscle metastasis.…”

Unusual metastases from differentiated thyroid cancers: A multicenter study in Korea

“…Some case reports and series have shown that synchronous UM in DTC patients presenting initially with UM-related symptoms, but they have difficulty in finding the primary cancer origin due to unusual metastatic sites [17]. However, the most of UMs from DTC were found to develop metachronously in previous studies [10,12].…”

FDG PET/CT in the Detection of Pancreatic Metastasis in a Patient with Follicular Thyroid Carcinoma and Negative I-131 Whole Body Scan Findings

“…While FTC usually remains localized to the thyroid gland, distant metastasis is observed in a minority of patients, with a reported incidence ranging from 4% to 15% (1)(2)(3). Metastatic FTC significantly contributes to disease morbidity and has been found to be associated with a 10-year survival of 40-45% (2).…”