Kidney tumor - adult malignancies - Carcinoid tumor of kidney

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Kidney tumor - adult malignancies

Other neoplasms – adult or adult/child

Carcinoid tumor of kidney

Reviewers: Sean Williamson, M.D. (see Reviewers page)
Revised: 17 July 2012, last major update June 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
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● 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

Epidemiology
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● 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 description
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● Average age 47 (Hum Pathol 2011;42:1554), usually NOT associated with carcinoid syndrome
● Often metastatic at presentation (Am J Surg Pathol 2007;31:1539)

Poor prognostic factors
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● Age >40 years, size >4 cm, >1 mitotic figure/10 HPF, metastasis at diagnosis, extension through renal capsule (J Urol 2006;176:2359)

Radiologic images
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CT scan shows mass with calcifications

Case reports
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● 30 year old woman with tumor in teratoma (Arch Pathol Lab Med 2002;126:979)
● 34 year old man (Arch Pathol Lab Med 1990;114:68)
● 60 year old man with renal mass (Case of Week #204)
● Renal tumor metastatic to liver (Arch Pathol Lab Med 1993;117:855)

Gross images
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4 cm lower pole mass

Micro description
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● 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
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Cords of uniform cells

Ribbons separated by sclerotic stroma

Insular pattern

Organoid pattern with classic nuclear features

Monotonous nuclei with fine chromatin

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

Various images

Cytology description
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● 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
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Clusters of monotonous cells with granular cytoplasm and round to oval nuclei (Diff-Quik)

Synaptophysin+ cells in cell block

Positive stains
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● CAM 5.2, vimentin, neuron-specific enolase, synaptophysin, chromogranin
● Also VEGF (Urol Oncol 2011;29:85), occasionally CK7, rarely CK20
● CD99 strongly positive in some cases, leading to challenging differential of PNET

Negative stains
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● TTF1, WT1, PAX2, PAX8

Electron microscopy description
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● Membrane-bound dense core granules

Electron microscopy images
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Prominent neurosecretory granules

Differential diagnosis
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● 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 Dec 14;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

End of Kidney tumor - adult malignancies > Adult renal cell carcinoma > Carcinoid tumor of kidney

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