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Year : 2017  |  Volume : 60  |  Issue : 1  |  Page : 105-107
Well differentiated neuroendocrine tumor of the kidney: Report of a rare case with review of literature

Department of Pathology, Indira Gandhi Medical College, Shimla, Himachal Pradesh, India

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Date of Web Publication14-Feb-2017


Neuroendocrine tumors (NETs) are uncommon tumors that exhibit a wide range of neuroendocrine differentiation and biological behavior. Primary NETs of the kidney, including carcinoid tumor, small cell carcinoma (SCC), and large cell neuroendocrine carcinoma (LCNEC) are exceedingly rare. Renal carcinoids are typically slow-growing tumors and pursue a variable clinical course. In contrast, SCC and LCNEC often present with locally advanced or metastatic disease and carry a poor prognosis. We herein report a rare cases of well-differentiated NET (carcinoid) in a 39-year-old male along with the immunohistochemical features. The rarity of these tumors poses a diagnostic and therapeutic challenge.

Keywords: Carcinoid, kidney, neuroendocrine tumor

How to cite this article:
Mardi K, Negi L, Srivastava S. Well differentiated neuroendocrine tumor of the kidney: Report of a rare case with review of literature. Indian J Pathol Microbiol 2017;60:105-7

How to cite this URL:
Mardi K, Negi L, Srivastava S. Well differentiated neuroendocrine tumor of the kidney: Report of a rare case with review of literature. Indian J Pathol Microbiol [serial online] 2017 [cited 2020 Aug 15];60:105-7. Available from: http://www.ijpmonline.org/text.asp?2017/60/1/105/200020

   Introduction Top

Neuroendocrine tumors (NETs) are uncommon tumors that exhibit a wide range of neuroendocrine differentiation and biological behavior. NETs can arise from any tissue or organ, including organs that do not normally contain neuroendocrine cells.[1] NETs represent a spectrum of diseases including well-differentiated NET (carcinoid), well-differentiated neuroendocrine carcinoma, poorly differentiated neuroendocrine carcinoma (large cell neuroendocrine carcinoma [LCNEC]), and small cell carcinoma (SCC). Primary NETs of the kidney, including carcinoid tumor, SCC, and LCNEC are exceedingly rare.[2] Renal carcinoids are typically slow-growing tumors and pursue a variable clinical course. We herein report a rare case of well-differentiated NET (carcinoid) in a 39-year-old male along with the immunohistochemical features and review the pertinent literature.

   Case Report Top

A 39-year-old male presented with dull aching pain in the left flank since 2 years. On per abdominal examination, there was no palpable lump. CECT abdomen showed a 10.4 cm × 6.7 cm, well-defined soft tissue mass seen in relation to left kidney, invading the cortex. Radiological diagnosis of renal cell carcinoma (RCC) was rendered, and the patient underwent left radical nephrectomy. Gross examination revealed soft necrotic growth replacing the renal parenchyma measuring 7 cm × 6 cm with friable tan, yellow appearance on cut section [Figure 1]. On microscopic examination, there was an extensive area of necrosis, with viable areas at periphery revealing, small round and regular tumor cells arranged in trabeculae, and anastomosing cords with peripheral palisading [Figure 2]. These tumor cells were possessing round to elongated nuclei with stippled nuclear chromatin, inconspicuous nucleoli, and moderate eosinophilic cytoplasm. Mitotic figures were scant (<2/10 HPF). Immunohistochemically, these tumor cells were diffusely positive for chromogranin [Figure 3]a synaptophysin [Figure 3]b and pancytokeratin [Figure 3]c and negative for WTI and TTFI. Ki-67 index was <1% [Figure 3]d. Thus, a diagnosis of well-differentiated NET, grade I (Carcinoid) was given.
Figure 1: Gross specimen showing necrotic tumor replacing the renal parenchyma

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Figure 2: Photomicrograph of renal carcinoid showing anastomosing trabeculae of tumor cells with uniform nuclei and stippled chromatin (H and E, ×20)

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Figure 3: (a-d) Tumor cells showing positivity for chromagrannin, synaptophysin, Pan-CK, and Ki-67 <1%

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   Discussion Top

NETs are most commonly seen in the gastrointestinal tract where it is most frequently localized in the small/large intestines and stomach. It is less frequent in the respiratory system. Sporadically, it is seen in parenchymal organs such as the liver. Primary NETs of the kidney are extremely rare.[2] They can occur in both the renal parenchyma and the renal pelvis.[3]

The pathogenesis of primary NETs of the kidney is still controversial. Neuroendocrine cells have been identified in the renal pelvis but not in the normal renal parenchyma.[4] Different theories support the fact that NETs arise from primitive totipotential stem cells that subsequently differentiate in a neuroendocrine direction. Several mechanisms have been used to explain the origin of such tumors, including metastasis from an occult primary tumor site to the kidney, activation of aberrant gene sequences in a totipotential stem cell line that differentiates into aberrant NET cells, and concurrent renal congenital abnormalities.[4],[5] el-Naggar et al.[4] reported a loss of heterozygosity at one locus on chromosome 3p21 in one case of carcinoid tumor and suggested that this anomaly (which is frequent in RCC) is a preliminary event that is common to all renal neoplasms including carcinoid tumors. NETs, essentially carcinoid tumors, are frequently associated with horseshoe kidney and teratomas. Romero et al.[5] reported horseshoe kidney in 10 patients (17.8%) and renal teratomas in eight patients (14.3%) concomitantly with carcinoid tumors. Some authors think that the tumors arise from neuroendocrine cells occurring in the mucosa of the renal pelvis in intestinal metaplasia.[5]

In 2010, the WHO has proposed a classification system for renal carcinoid tumors that is similar to that of the carcinoid tumors of other organs.[6] They classified neuroendocrine neoplasms into NET-well differentiated grade 1, NET-well differentiated grade 2, NEC-poorly differentiated grade 3 (small and large cell type), mixed adenoneuroendocrine carcinoma, hyperplastic, and preneoplastic lesions. This classification differentiates between NETs and neuroendocrine carcinomas. The proliferation index (Ki-67, MIB-1), angioinvasion, and mitoses are important factors in this classification. Thus, tumors are divided into well-differentiated NETs (<2 cm in size, <2% Ki-67 index), well-differentiated neuroendocrine carcinomas (>2 cm in size, >2% Ki-67 index, or angioinvasive), and poorly differentiated neuroendocrine carcinomas (>20% Ki-67 index).

Well-differentiated NET (carcinoid) of the kidney are rare with <100 cases reported in the literature so far.[5],[7] These are slow growing and nonfunctional in most cases. They may remain silent for many years before manifesting any symptoms and are often incidentally detected. These tumors show no gender predilection, and occur in patients between the ages of 23 and 78 years, with a mean age of occurrence that is lower than for RCC.[7]

The size of primary carcinoid tumors of the kidney ranges from 2 to 16 cm. Previous findings suggest a range from 1.5 to 30 cm.[5] These neoplasms with indolent course are usually diagnosed at a large size with approximately 75% >4 cm. This could be due to the vacuous nature of the retroperitoneal space as kidneys are essentially retroperitoneal organs.

A diagnosis of carcinoid tumor is rarely suspected in patients with renal cortical neoplasms before surgery as the clinical features of these patients are similar to those with other renal neoplasms. In an extensive review of 56 cases of renal carcinoid by Romero et al.,[5] it was found that median patient age was 49 years. Horseshoe kidneys were present in 17.8% of cases. Incidental diagnosis was made in 28.6% of patients. The most common symptom was an abdominal or flank pain, and neuroendocrine syndromes occurred with only 12.7% of primary renal carcinoid tumors. Of the patients 73.6% presented with tumors larger than 4 cm. Metastases were present in 45.6% of patients at initial diagnosis, and almost 60% with tumors >4 cm had metastases.

Significant adverse prognostic factors include age >40 years, tumor size >4 cm, purely solid tumors on the cut surface, mitotic rate higher than 1/10 HPF, metastasis at initial diagnosis and tumors extending throughout the renal capsule.[5] There is no clear correlation between the histologic features of the disease and prognosis and tumor necrosis is not a predictor of prognosis. Metastatic workup must always be done to rule out the possibility of metastasis from an occult tumor elsewhere when a clinical diagnosis of renal carcinoid is made. Long-term follow-up care is essential because of the prolonged course of disease despite metastasis.

The clinical course of renal carcinoid is difficult to predict because of the rarity of the condition; however, it is largely believed to have an indolent course. The current recommended management for primary renal carcinoid tumors includes radical nephrectomy with surveillance and surgical removal of any subsequent metastases.[6] Even partial nephrectomy is recommended for small tumors. The average follow-up time is 20 months with 73.1% of patients without evidence of disease after surgical treatment which suggests that surgical treatment is curative.[8],[9] Liver metastasis can be treated with open resection or with minimally invasive ablative procedures. Metastatic renal carcinoid has been noted to be resistant to chemotherapy.

   Conclusion Top

Diagnosis of NETs requires awareness of their rare occurrence and prudent use of immunohistochemical neuroendocrine markers. Renal carcinoid tumors are indolent and are associated with prolonged survival.

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Conflicts of interest

There are no conflicts of interest.

   References Top

DeLellis RA, Osamura RY. Neuroendocrine tumors: An overview. Pathol Case Rev 2006;11:229-34.  Back to cited text no. 1
Lane BR, Jour G, Zhou M. Renal neuroendocrine tumors. Indian J Urol 2009;25:155-60.  Back to cited text no. 2
[PUBMED]  Medknow Journal  
Kuroda N, Katto K, Tamura M, Shiotsu T, Hes O, Michal M, et al. Carcinoid tumor of the renal pelvis: Consideration on the histogenesis. Pathol Int 2008;58:51-4.  Back to cited text no. 3
el-Naggar AK, Troncoso P, Ordonez NG. Primary renal carcinoid tumor with molecular abnormality characteristic of conventional renal cell neoplasms. Diagn Mol Pathol 1995;4:48-53.  Back to cited text no. 4
Romero FR, Rais-Bahrami S, Permpongkosol S, Fine SW, Kohanim S, Jarrett TW. Primary carcinoid tumors of the kidney. J Urol 2006;176 (6 Pt 1):2359-66.  Back to cited text no. 5
Eble JN, Sauter G, Epstein JL. World Health Organization Classification of Tumours. Pathology and Genetics of Tumors of the Urinary System and Male Genital Organs. Lyon: IARC Press; 2004. p. 81-2.  Back to cited text no. 6
Omiyale AO, Venyo AK. Primary carcinoid tumour of the kidney: A review of the literature. Adv Urol 2013;2013:579396.  Back to cited text no. 7
Raslan WF, Ro JY, Ordonez NG, Amin MB, Troncoso P, Sella A, et al. Primary carcinoid of the kidney. Immunohistochemical and ultrastructural studies of five patients. Cancer 1993;72:2660-6.  Back to cited text no. 8
Cabral Ribeiro J, Sousa L, Ribeiro Santos A. Primary neuroendocrine tumor of the kidney. Actas Urol Esp 2010;34:907-9.  Back to cited text no. 9

Correspondence Address:
Dr. Kavita Mardi
Set No 14, Type VI Quarters, IAS Colony, Meheli, Shimla, Himachal Pradesh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0377-4929.200020

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