Multifocal Renal Carcinoid Tumor Arising in Horseshoe Kidney with Metastases to the Thyroid

Renal neuroendocrine tumors: clinical and molecular pathology with an emphasis on frequent association with ectopic Cushing syndrome

Renal neuroendocrine tumors (RenNETs) are rare malignancies with largely unknown biology, hormone expression, and genetic abnormalities. This study aims to improve our understanding of the RenNETs with emphasis of functional, hormonal, and genetic features. Surgically resected RenNETs (N = 13) were retrieved, and immunohistochemistry and next-generation sequencing (NGS) were performed in all cases. In addition, all published RenNETs were systematically reviewed. Our cohort (4 men and 9 women, mean age 42, mean tumor size 7.6 cm) included 2 patients with Cushing syndrome (CS). WHO grade (23% G1, 54% G2, and 23% G3) and tumor progression did not correlate. CS-associated RenNETs (CS-RenNETs) showed a solid and eosinophilic histology and stained for ACTH, while the remaining non-functioning tumors had a trabecular pattern and expressed variably hormones somatostatin (91%), pancreatic polypeptide (63%), glucagon (54%), and serotonin (18%). The transcription factors ISL1 and SATB2 were expressed in all non-functioning, but not in CS-RenNETs. NGS revealed no pathogenic alterations or gene fusions. In the literature review (N = 194), 15 (8%) of the patients had hormonal syndromes, in which CS being the most frequent (7/15). Large tumor size and presence of metastasis were associated with shorter patients' survival (p < 0.01). RenNETs present as large tumors with metastases. CS-RenNETs differ through ACTH production and solid-eosinophilic histology from the non-functioning trabecular RenNETs that produce pancreas-related hormones and express ISL1 and SATB2. MEN1 or DAXX/ARTX abnormalities and fusion genes are not detected in RenNETs, indicating a distinct yet unknown molecular pathogenesis.

An update on the current epidemiological status of metastatic neoplasms to the thyroid

Secondary tumours to the thyroid gland are uncommon with an overall prevalence of 5.9% in autopsy studies. In recent clinical series, secondary thyroid cancer is seen in only 1.9% of malignant thyroids. There is no gender predominance both overall (female to male 1.07:1) and when stratified by common histological subtypes (renal cell carcinoma, lung adenocarcinoma and colorectal adenocarcinoma). The median age of patients diagnosed with metastatic thyroid tumours in major studies ranges from 54 to 68 years. Metastases are more frequent in patients with pre-existing or concurrent thyroid pathology. In autopsy studies, the most common primary sites are breast carcinoma and lung carcinoma. Renal cell carcinoma, lung carcinoma and breast carcinoma predominate in clinical series. Upper aerodigestive tract primaries often directly infiltrate the thyroid gland. The underlying frequency of a histological subtype, geographic prevalence and aggressiveness of primary cancer likely contributes to the incidence of metastasis in the thyroid gland. This is seen in case series from Asia where gastric and oesophageal primary cancers predominate. Secondary thyroid cancer can present metachronously (60%), synchronously (34%), or as the first presentation of the underlying cancer (6%). Late metastases and first clinical presentations of disease often originate from renal cell carcinomas while synchronous cases tend to originate from the lungs. Other common primary sites for first presentation of secondary thyroid cancer include the lung and oesophagus. Although rare, secondary thyroid cancer should be considered as a differential particularly in patients with previous malignancy, such as from the kidney, lung, or breast.

Clinical and Pathological Features of Primary Renal Well-Differentiated Neuroendocrine Tumor

Primary carcinoid tumor of the kidney is an extremely rare well-differentiated neuroendocrine tumor, which is generally a low-grade malignant cancer with a good prognosis. Carcinoid tumors are rarely found in the urinary system. Here, we report a 34-year-old woman with primary renal well-differentiated neuroendocrine tumor who underwent nephron sparing surgery and no evidence of recurrence or distant metastasis was found during routine follow-up. We searched the case of renal carcinoid with the search phrase "carcinoid [title] and kidney [title]" and "carcinoid [title] and renal [title]" using the PubMed and restricted the search to articles published in English since 2013. The clinical manifestations, age, sex, tumor size, location, gross pathology, light microscopy and immunohistochemistry were analyzed. A total of 28 cases of renal carcinoid were retrieved from PubMed. Higher proportion of positive labeling of CgA, Syn, NSE and CD56 are most valuable in the diagnosis of primary renal well-differentiated neuroendocrine tumor. At present, radical nephrectomy remains the gold standard in the curative-intent therapy for well-differentiated neuroendocrine carcinoma of kidney, in metastatic renal carcinoid, long-term use of octreotide may be an effective adjuvant therapy.