Kidney tumor
Other adult malignancies
WD Neuroendocrine tumor (carcinoid)

Author: Sean Williamson, M.D. (see Authors page)

Revised: 9 February 2017, last major update June 2012

Copyright: (c) 2003-2017,, Inc.

PubMed Search: WD Neuroendocrine tumor

Cite this page: WD Neuroendocrine tumor (carcinoid). website. Accessed February 19th, 2017.
Definition / General
  • Very rare, low grade (well differentiated) neuroendocrine tumor with finely granular cytoplasm, uniform nuclei and stippled chromatin
  • Similar morphology to neuroendocrine tumors of other organs, though without a definitive cell of origin (Hum Pathol 2011;42:1554)
  • Also called low grade neuroendocrine carcinoma
  • Rare, < 100 cases reported; associated with horseshoe kidney, which has an increased risk of renal tumors in general or renal teratoma (Pol J Pathol 2011;62:72)
Clinical Features
Radiology Images

Images hosted on other servers:

CT scan shows mass with calcifications

Contributed by Dr. Ricardo Drut, Argentina

Prognostic Factors
  • Age > 40 years, size > 4 cm, > 1 mitotic figure / 10 HPF, metastasis at diagnosis, extension through renal capsule (J Urol 2006;176:2359)
Case Reports
Gross Images

Images hosted on PathOut server:

4 cm lower pole mass

Micro Description
  • Pure or associated with teratoma
  • Usually well demarcated but may have focal infiltration
  • Extracapsular extension in 52%
  • Tightly packed cords, trabeculae with variable stroma, nests or ribbons; uniform cells with eosinophilic, finely granular cytoplasm and uniform nuclei with stippled chromatin
  • Often calcifications; no / rare mitotic activity, no necrosis
Micro Images

Images hosted on PathOut server:

Insular pattern

Organoid pattern with classic nuclear features

H&E (left two images), CD56 and chromogranin

Images hosted on other servers:

Various images

Contributed by Dr. Ricardo Drut, Argentina

Cytology Description
  • Monotonous plasmacytoid cells arranged singly and in small clusters
  • Occasional cells in acinar pattern resembling glandular differentiation
  • Tumor cells have fine speckled chromatin (Diagn Cytopathol 2007;35:306)
Cytology Images

Images hosted on other servers:

Monotonous cells with granular cytoplasm

Clusters with round to oval nuclei

Staining consistent with neuroendocrine differentiation

Positive Stains
Negative Stains
Electron Microscopy Description
  • Membrane bound dense core granules
Electron Microscopy Images

Images hosted on PathOut server:

Prominent neurosecretory granules

Differential Diagnosis
  • Metanephric adenoma: negative for neuroendocrine markers synaptophysin, chromogranin, CD56
  • Metastatic carcinoid tumor: clinical history of carcinoid tumor elsewhere, renal metastases may be multiple (BMC Urol 2010;10:22)
  • Neuroblastoma: may have neurofibrillary stroma, Homer-Wright pseudorosettes, catecholamine production
  • Papillary renal cell carcinoma: often foamy macrophages, no neuroendocrine nuclear features, negative for neuroendocrine markers synaptophysin, chromogranin, CD56
  • PNET: challenging due to overlap in expression of CD99, positive FISH for EWSR1 rearrangement may be helpful
  • Small cell carcinoma of kidney: high grade atypia with scant cytoplasm, molding, high mitotic / proliferative index