Kidney tumor

Adult renal cell carcinoma - rare

Primary thyroid-like follicular



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PubMed Search: Thyroid-like follicular carcinoma

Daniel Anderson, M.D., M.B.A.
Maria Tretiakova, M.D., Ph.D.
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Cite this page: Anderson D, Tretiakova M. Primary thyroid-like follicular. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/kidneytumormalignantprimarythyroidlike.html. Accessed December 1st, 2022.
Definition / general
Essential features
  • Extremely uncommon (~40 cases reported)
  • Resembles well differentiated thyroid follicular neoplasms
  • Encapsulated mass with thyroid-like follicles (macro and microfollicles) containing inspissated, eosinophilic colloid-like material
  • Negative for TTF1 and thyroglobulin
  • Most have low malignant potential
Terminology
  • Thyroid-like follicular renal cell carcinoma
ICD coding
  • ICD-10: C64.9 - malignant neoplasm of unspecified kidney, except renal pelvis
Epidemiology
Sites
  • Renal cortex
Clinical features
  • Asymptomatic and found incidentally in most but may be symptomatic (hematuria, flank pain, abdominal pain) in up to 33% of patients (Pathology 2018;50:24)
Diagnosis
Radiology description
Radiology images

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Noncontrast coronal CT with 5.7 cm mass

Noncontrast coronal CT with 5.7 cm mass

Noncontrast axial CT with 2.5 cm mass

Noncontrast axial CT with 2.5 cm mass

Postcontrast axial CT without evidence of enhancement

Postcontrast axial CT without evidence of enhancement

Coronal and axial (contrast) CT scans

Coronal and axial (contrast) CT scans

Prognostic factors
Case reports
Treatment
  • Partial or radical nephrectomy
Gross description
Gross images

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Partially cystic, hemorrhagic mass

Partially cystic, hemorrhagic mass

Multiloculated cystic mass

Multiloculated cystic mass

Microscopic (histologic) description
  • Follicular-like architecture with variably sized follicles, with micro and macrofollicles, containing inspissated, eosinophilic colloid-like material
  • Follicles are lined by a single layer of cuboidal or low columnar epithelium with moderate amphophilic to eosinophilic cytoplasm, round nuclei, mostly inconspicuous to occasionally prominent nucleoli
  • Majority of tumors show pure follicular architecture, with some variations including branching, resulting in focal papillary-like pattern (Mod Pathol 2021;34:1167)
  • Papillary areas appear to be broken interfollicular septa rather than true papillae (Pathology 2018;50:24)
  • May be cystically dilated (Diagn Pathol 2014;9:186)
  • May have focal tightly packed follicles without secretions, imparting a somewhat solid appearance
  • Few cases demonstrate nuclear grooves or ground glass nuclear appearance (Pathology 2018;50:24)
  • Lymphocytic infiltrate may be present intratumorally or around periphery and macrophages may be present in background (Diagn Pathol 2013;8:108)
  • Calcifications may be seen (Pathology 2018;50:24)
  • Necrosis and lymphovascular invasion are absent in most tumors
  • Sarcomatoid differentiation has been reported (Int J Surg Pathol 2019;27:678, Int J Surg Pathol 2021;29:327, Histopathology 2022;80:745)
Microscopic (histologic) images

Contributed by Maria Tretiakova, M.D., Ph.D.
Atrophic appearance

Atrophic appearance

Variably sized follicles

Variably sized follicles

Cytology description
  • May be hypercellular and arranged in sheets (Diagn Cytopathol 2014;42:273)
  • Presence of acellular eosinophilic material is associated with the neoplastic epithelial cells in the background of the smear
  • Individual tumor cells may be oval, round and plasmacytoid with mild nuclear pleomorphism, finely stippled nuclear chromatin and inconspicuous nucleoli with a moderate amount of eosinophilic cytoplasm and rare nuclear grooves (Diagn Cytopathol 2014;42:273, Diagn Pathol 2013;8:108)
Cytology images

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Giemsa

Giemsa

Uniform, medium sized cells

Uniform, medium sized cells

Negative stains
Molecular / cytogenetics description
  • In 3 of 3 tumors tested in one study, an in frame fusion of exon 8 of EWSR1 and intraexonic of PATZ1, both on chromosome 22, were detected by RNA sequencing and confirmed with reverse transcription PCR; per authors, other approaches instead of FISH may be preferable to detect the EWSR1::PATZ1 fusion (Mod Pathol 2021;34:1921, Histopathology 2022;80:745)
  • Gene expression profile is distinct from clear cell and chromophobe renal cell carcinoma
  • Amin et al. reported overexpression in cell cycle regulatory genes and mixed lineage leukemia (MLL) / trithorax homolog in 3 tumors; however, comparative genetic hybridization failed to reveal cytogenetic alterations in one study (Am J Surg Pathol 2009;33:393)
  • Another study showed chromosomal gains of 7q36, 8q24, 12, 16, 17p11-q11, 17q24, 19q, 20q13, 21q22.3 and Xp and losses of 1p36, 3 and 9q21-33 detected by comparative genomic hybridization (Am J Surg Pathol 2006;30:411)
Molecular / cytogenetics images

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<i>EWSR1::PATZ1</i> schematic

EWSR1::PATZ1 schematic

Sample pathology report
  • Right kidney, partial nephrectomy:
    • Thyroid-like follicular renal cell carcinoma (2.2 cm) (see synoptic report and comment)
    • Comment: The tumor cells are positive for PAX8, CK7 and are negative for TTF1, thyroglobulin and WT1.
Differential diagnosis
Board review style question #1

A 42 year old woman undergoes a left radical nephrectomy for a 4 cm renal mass. Which of the following is most consistent with a diagnosis of thyroid-like follicular renal cell carcinoma?

  1. Grossly well circumscribed renal tumor with microscopic follicular growth and inspissated colloid-like material
  2. Immunohistochemistry demonstrates tumor cells to be negative for PAX8 and CK7 and positive for WT1
  3. Poor clinical prognosis after diagnosis with high mortality rate
  4. Will demonstrate NRAS and HRAS or BRAF mutations by sequencing
Board review style answer #1
A. Grossly well circumscribed renal tumor with microscopic follicular growth and inspissated colloid-like material. Thyroid-like follicular renal cell carcinoma usually presents asymptomatically over a wide age range with female predominance. On gross, the tumor is well circumscribed tan to brown, solid to cystic mass. Microscopically, it demonstrates follicular-like architecture with micro and macrofollicles, filled with inspissated colloid-like material. The follicles are lined by cuboidal cells with moderate amount of amphophilic to eosinophilic cytoplasm, oval nuclei with uniform chromatin and inconspicuous nucleoli. This entity typically has an indolent clinical behavior. Immunohistochemical profile is typically PAX8+ / CK7+ / WT1- / TTF1- / thyroglobulin-, in contrast to atrophic kidney-like tumor / lesion and metastatic thyroid carcinoma, the 2 closest morphologic mimics. The tumor will be negative for NRAS, HRAS and BRAF mutations, in contrast to metastatic thyroid carcinoma.

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Reference: Primary thyroid-like follicular carcinoma
Board review style question #2

A 65 year old woman undergoes a right radical nephrectomy for a 3 cm renal mass. The tumor displays follicular architecture with inspissated colloid-like material without papillary-like nuclear features or papillary growth. By immunohistochemistry, the tumor cells are positive for TTF1 and thyroglobulin. This patient will likely have which of the following?

  1. An intact thyroid with no nodules
  2. No evidence of other metastatic foci on PET / CT
  3. PAX8 IHC negativity
  4. RAS mutation
Board review style answer #2
D. RAS mutation. The question describes a metastatic follicular carcinoma of the thyroid. These patients will typically have evidence of prior thyroid surgery or an obvious thyroid primary with widely metastatic disease. The most common somatic mutations to occur in follicular thyroid carcinoma are RAS point mutations (most often codon 61 of NRAS and codon 61 of HRAS) followed by PPARG gene fusions (e.g., PAX8::PPARG). RAS mutations are found in almost half of conventional follicular carcinomas. They stabilize the protein in its active guanosine triphosphate (GTP) bound form, leading to constant stimulation of the downstream signaling pathways, particularly MAPK and PI3K / AKT cascades. Both metastatic thyroid-like follicular renal cell carcinoma and metastatic follicular carcinoma of the thyroid will demonstrate PAX8 positivity and therefore this stain should not be used to distinguish between these entities.

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Reference: Primary thyroid-like follicular carcinoma
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