Renal Cell Carcinoma Presenting as Isolated Thyroid Metastasis 13 Years After Radical Nephrectomy, Detected on F-18 FDG PET/CT

A Multimodal and Pathological Analysis of a Renal Cell Carcinoma Metastasis to the Thyroid Gland 11 Years Post Nephrectomy

Thyroid lesions have a comprehensive differential diagnosis which include benign and malignant entities, such as metastases. However, metastases only account for a small percentage of thyroid lesions with renal cell carcinoma as the most common. Metastases to the thyroid pose a diagnostic dilemma as symptoms may not manifest for up to decades after removal of the renal cell carcinoma. Due to the nonspecific appearance on computed tomography and ultrasound, distinguishing metastases from primary thyroid malignancies is of the utmost importance for timely patient management. Our case demonstrates the importance of considering RCC metastases to the thyroid even years after nephrectomy to mitigate potential delays in diagnosis. We present the case of a 66-year-old male with a past medical history of renal cell carcinoma status post nephrectomy 11 years prior who demonstrated incidental thyroid abnormalities on positron emission tomography/computed tomography and ultrasound later confirmed as a metastasis of renal cell carcinoma.

18F-PET/CT imaging of metastasis to the thyroid gland: Imaging findings and effect on patient management

Purpose

While metastasis to the thyroid from a primary cancer remote to the thyroid is uncommon, current imaging techniques have improved detection of these intrathyroid metastases. The purpose of this study was to evaluate the ¹⁸F-PET/CT appearance of intrathyroid metastases and assess the impact of detection on patient management.

Methods

The ¹⁸F-PET/CT appearance of intrathyroid metastasis, including standardized uptake value (SUV), disease extent, and the effect on patient management following diagnosis were retrospectively reviewed. Inclusion criteria included ¹⁸F-PET/CT imaging and diagnosis of the intrathyroid metastasis matching the remote primary tumor.

Results

Intrathyroid metastasis were detected in 24 patients. The intrathyroid metastases presented on ¹⁸F-PET/CT as focal nodular uptake (n = 21), multiple nodular uptake (n = 2), or diffuse uptake/infiltration of the thyroid gland (n = 1). The SUV ranged between 3.9 and 42 (median 12.5 ± 7.5); in 2 patients, the FDG-avidity was minimal. On ¹⁸F-PET/CT, distant metastases were present outside the neck (n = 18), or limited to the neck (n = 6). In 2 of these 6 patients, the thyroid was the only site of metastatic disease. Due to the metastatic disease, the therapy was changed in 23 of 24 patients; 1 patient was lost to follow-up.

Conclusion

In any patient with a previous or current history of an extrathyroid malignancy, an ¹⁸FDG-avid thyroid mass or diffuse infiltration of the thyroid on ¹⁸F-PET/CT should be considered a potential intrathyoid metastasis until proven otherwise. Knowledge of an intrathyroid metastasis may impact patient management, especially if the thyroid or neck are the only sites of metastatic disease.

Metastatic carcinoma to the thyroid gland: a single institution 20-year experience and review of the literature

The thyroid gland is an uncommon site for metastatic disease but cases have been well-documented in the literature, particularly in autopsy series. A retrospective review of surgical pathology and autopsy pathology database for patients with metastatic carcinoma to the thyroid was performed at the University of Massachusetts Medical Center between January 1993 to January 2013. We identified a total of 10 patients with metastatic carcinoma to the thyroid; 6 were in surgical pathology specimens out of a total of 1,295 thyroid carcinoma (0.46 %) and 4 were diagnosed at autopsy out of a total of 2,117 (0.19 %) autopsy cases during this period. Cases with direct extension of the tumor into the thyroid from local primary sites such as larynx, esophagus or soft tissues of the neck were excluded. The primary tumors in these cases comprised of four lung carcinomas, three colorectal carcinomas, a renal cell carcinoma, a pleural malignant mesothelioma, and an unknown primary. Therefore, it is important to keep intrathyroidal metastases in the differential diagnosis when evaluating a thyroid nodule, particularly in patients with a previous history of malignancy. Furthermore, a literature review reveals over 1,400 cases have been previously reported, with the most common malignancies from the kidney (34 %), lung (15 %), gastrointestinal tract (14 %), and breast (14 %).

Usefulness of (18)F-FDG PET/CT in a rare case of malignant pseudothyroiditis

We report an unusual case of malignant pseudothyroiditis (MPT) occurred in a 35-year-old female patient presenting with symptoms and signs of thyroiditis. Fine-needle aspiration biopsy of the thyroid demonstrated the presence of a MPT induced by a metastatic extrathyroidal carcinoma. F-FDG-PET/CT showed increased radiopharmaceutical uptake in the thyroid, in multiple cervical and mediastinal lymph nodes, and in a right pulmonary nodule. Histological examination demonstrated the presence of a metastatic non-small cell lung cancer (NSCLC). In this unusual case of MPT F-FDG-PET/CT has been useful in staging the disease and in detecting the primary tumor site.

Renal cell carcinoma with unusual metastasis to the small intestine manifesting as extensive polyposis: successful management with intraoperative therapeutic endoscopy

We present here a rare clinical case of a 53-year-old gentleman with metastasis from renal cell carcinoma (RCC) to the small intestine presenting with extensive polyposis and massive gastrointestinal bleeding which was successfully managed with intraoperative endoscopic polypectomy and segmental small bowel resection. The patient presented with melena 2 weeks after right nephrectomy for RCC. Capsule endoscopy found extensive polyposis throughout the small bowel, and the histological features confirmed the diagnosis of metastatic RCC. The patient eventually underwent laparotomy with intraoperative endoscopy of the entire small bowel. Most of the polyps were removed by snare polypectomy. Three segments of the small bowel with extensive transmural involvement had to be resected with primary anastomosis. In the 2 months following his surgery, the patient had no further evidence of gastrointestinal bleeding. The decision of meticulously removing close to 100 polyps by intraoperative endoscopy prevented the patient from requiring total small bowel resection and lifelong dependence on parenteral nutrition. In conclusion, gastrointestinal bleeding in a patient with known RCC should always trigger full gastrointestinal work-up including capsule endoscopy and, if necessary, double balloon enteroscopy.