Kidney tumor

Benign adult tumors

Well differentiated neuroendocrine tumor (carcinoid)

Last author update: 28 December 2021
Last staff update: 11 November 2022

Copyright: 2003-2023,, Inc.

PubMed Search: Well differentiated neuroendocrine kidney tumor

Lin Cheng, M.D., Ph.D.
Maria Tretiakova, M.D., Ph.D.
Page views in 2022: 2,056
Page views in 2023 to date: 1,054
Cite this page: Cheng L, Tretiakova M. Well differentiated neuroendocrine tumor (carcinoid). website. Accessed June 7th, 2023.
Definition / general
  • Well differentiated epithelial neoplasm arising from renal parenchyma and showing neuroendocrine differentiation
Essential features
  • Rare tumor arising from renal parenchyma; associated with horseshoe kidney and mature teratoma of kidney
  • Expresses neuroendocrine markers histologically but most are clinically nonfunctional
  • Distant metastasis is common at diagnosis and Dual Tracer PET imaging (DOTATATE scan) can help identify metastases
  • Carcinoid tumor, atypical carcinoid tumor
ICD coding
  • ICD-O: 8240/3 - well differentiated neuroendocrine tumor
  • ICD-10: C7A.093 - malignant carcinoid tumor of the kidney
  • ICD-11: 2C90.Y - other specified malignant neoplasms of kidney, except renal pelvis
  • Arises from renal parenchyma; can extend into renal pelvis and inferior vena cava (Urology 2020;135:e2)
  • Uncertain
Clinical features
  • Imaging study followed by histological examination of biopsy or resection specimen
Radiology description
Radiology images

Images hosted on other servers:

Right renal mass

Enhancing right renal mass

Tumor extending into IVC

Cystic tumor

Slightly hyperdense tumor

Metastases on DOTATATE scan

Prognostic factors
  • Unfavorable prognostic factors:
    • Age: > 40 years
    • Size: > 4 cm
    • > 1 mitotic figure/10 high power fields (HPF)
    • Metastasis at diagnosis
    • Extension throughout renal capsule
  • Reference: J Urol 2006;176:2359
Case reports
Gross description
  • Well circumscribed, soft, brown-tan mass with focal hemorrhage, necrosis or cystic degeneration
Gross images

Contributed by Jennifer Jeung, M.D. (Case #204)
Tan, soft, well encapsulated mass in lower pole Tan, soft, well encapsulated mass in lower pole

Tan, soft, well encapsulated mass in lower pole

Images hosted on other servers:

Tumor in horseshoe kidney

Renal mass with hemorrhage

Necrotic renal mass

Tumor involving sinus fat

Cystic renal mass

Microscopic (histologic) description
  • Variable architecture: tightly packed cords with minimal stroma (most common, 81%), sheet-like / solid pattern, nests / organoid pattern, trabeculae, ribbons, pseudo glands, etc. (Am J Surg Pathol 2007;31:1539)
  • Round to oval / elongated nuclei with stippled / speckled chromatin, inconspicuous nucleoli and moderate eosinophilic / granular cytoplasm
  • Occasional calcifications (5/21, 24%) of variable sizes (Am J Surg Pathol 2007;31:1539)
  • Usually lack of necrosis and low mitotic activity (< 4/10 HPF)
  • Grading of well differentiated neuroendocrine tumor of kidney is not clearly defined in WHO 2016 classification; mitotic counts and the Ki67 index may be good markers (Diagn Pathol 2019;14:12)
Microscopic (histologic) images

Contributed by Maria Tretiakova, M.D., Ph.D. and Sleiman Khalil, M.D.

Well demarcated tumor

Nests and pseudoglands

Monotonous tumor cells

Positive synaptophysin

Positive chromogranin

Positive CD99

Contributed by Leandro Freitas, M.D., Ana Grizotto, M.D., Athanase Billis, M.D. and the Genitourinary Pathology Society (Case #521)

Classic appearance

Prominent stroma

Prominent stroma

Areas of solid growth

Areas of solid growth

Gland-like lumina

Gland-like lumina

Synaptophysin, chromogranin, CAM5.2

Synaptophysin, chromogranin, CAM5.2

Cytology description
Cytology images

Images hosted on other servers:

Monotonous cells

Positive synaptophysin stain

Granular cytoplasm

Positive stains
Negative stains
Electron microscopy description
  • Presence of dense core neurosecretory granules
Electron microscopy images

Contributed by Jennifer Jeung, M.D. (Case #204)

TEM of tumor cells

Prominent neurosecretory granules

Molecular / cytogenetics description
  • Genetic alterations are variable and none of them are specific
  • Most frequently observed genetic changes are mutations in CDH1 and TET2
  • Reference: Histopathology 2019;75:104
Sample pathology report
  • Right kidney, core biopsy:
    • Well differentiated neuroendocrine tumor, likely renal primary (see comment)
    • Comment: The tumor cells show nested growth pattern, with round to oval nuclei, stippled chromatin and eosinophilic granular cytoplasm. No mitosis or necrosis is seen. Immunohistochemistry studies show that the tumor cells are positive for CK AE1 / AE3, synaptophysin and chromogranin and negative for PAX8, TTF1, CDX2 and GATA3. The overall findings are consistent with a well differentiated neuroendocrine tumor. Given the radiographic finding of solitary renal mass and lack of clinical history of neuroendocrine tumors elsewhere, this tumor is most likely a renal primary.
Differential diagnosis
  • Metastatic well differentiated neuroendocrine tumor:
    • Clinical history of well differentiated neuroendocrine tumor in other body sites
    • May show TTF1 or CDX2 positivity
  • Paraganglioma:
    • Zellballen / organoid growth pattern
    • Sustentacular cells are positive for S100 and chief cells are positive for neuroendocrine markers
    • Negative for cytokeratin and positive for GATA3 (Mod Pathol 2013;26:1365)
  • Metanephric adenoma:
    • Composed of tightly packed tubules, ducts and abortive glomeruli; psammomatous calcifications are common
    • Positive for PAX8, BRAF and WT1
  • Nested variants of urothelial carcinoma:
    • Variable sized anastomosing nests with irregular projection into stroma
    • Positive for CK7, CK20, GATA3 and uroplakin II
  • High grade neuroendocrine tumor of kidney:
    • High grade cytological atypia, necrosis is common; brisk mitotic activity and high Ki67 proliferative index
    • Positive for cytokeratin and neuroendocrine markers
    • Small cell carcinoma: high N/C ratios, hyperchromatic nuclei, nuclear molding
    • Large cell carcinoma: large nuclei, abundant cytoplasm, prominent nucleoli
  • Ewing sarcoma:
    • Usually in children or young adults < 20 years old
    • Small round blue cell tumor, CD99 positive
    • Gene rearrangements involving FET and ETS families of genes (most commonly EWSR1-FLI1 gene rearrangement)
Board review style question #1

A 45 year old man presented with hematuria. CT showed a well demarcated 3 cm left renal mass in the lower pole. Core biopsy was performed and the H&E slide is above. Immunostains show that the tumor cells are positive for CK8/18, synaptophysin and chromogranin and negative for PAX8, GATA3 and S100. What is the diagnosis of this tumor?

  1. Metanephric adenoma
  2. Nested variant of urothelial carcinoma
  3. Papillary renal cell carcinoma
  4. Paraganglioma
  5. Well differentiated neuroendocrine tumor
Board review style answer #1
E. Well differentiated neuroendocrine tumor

Comment Here

Reference: Well differentiated neuroendocrine tumor of kidney (carcinoid)
Board review style question #2
Which of the following immunostains is usually negative in well differentiated neuroendocrine tumor but positive in paraganglioma?

  1. CD56
  2. CD99
  3. Chromogranin
  4. GATA3
  5. Synaptophysin
Back to top
Image 01 Image 02