20 November 2024 - Case of the Month #544
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Thanks to Dr. Alcino Pires Gama and Dr. Bonnie Choy, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA for contributing this case and discussion and to Dr. Maria Tretiakova, University of Washington, Seattle, Washington, USA for reviewing the discussion.
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Case of the Month #544
Clinical history:
A 56 year old patient with a 4.5 cm right renal mass underwent a partial nephrectomy.
Microscopic images:
What is your diagnosis?
Diagnosis: Eosinophilic vacuolated tumor
Test question (answer at the end):
Which of the following is true about eosinophilic vacuolated tumor (EVT)?
Stains:
Discussion:
In the 5th edition of the WHO Classification of Tumors, eosinophilic vacuolated tumor (EVT) is categorized under other oncocytic tumors of the kidney, a heterogeneous group of oncocytic tumors that are not classifiable as oncocytoma, chromophobe renal cell carcinoma (RCC) or other eosinophilic entities (WHO Classification of Tumours Editorial Board: Urinary and Male Genital Tumours, 5th Edition, 2022). EVTs typically present in adults of a broad age range. While almost all of the cases are sporadic, it has been reported in a patient with tuberous sclerosis complex (Histopathology 2019;75:440). Relatively limited follow up has not found evidence of recurrence or metastatic potential following resections of EVTs (Virchows Arch 2018;473:725, Mod Pathol 2022;35:344).
The tumors are well circumscribed but unencapsulated, with an average tumor size of 4.3 cm (Mod Pathol 2022;35:344). Histologically, EVTs have nested to solid growth with focal tubulocystic features, composed of eosinophilic cells with large intracytoplasmic vacuoles and prominent nucleoli, imparting a high grade appearance (Virchows Arch 2018;473:725, Am J Surg Pathol 2019;43:121, Mod Pathol 2022;35:344). Entrapped renal tubules and large vessels can be found at the periphery.
Immunohistochemically, EVTs are positive for PAX8, cathepsin K, CD117, CD10, SDH (retained), and FH (retained), while negative for CK7 (except rare cells), CK20, MelanA, HMB45 and TFE3 (Virchows Arch 2018;473:725, Am J Surg Pathol 2019;43:121, Mod Pathol 2022;35:344). EVTs are associated with somatic biallelic mutations in mTOR pathway genes (TSC1, TSC2 or MTOR) (Am J Surg Pathol 2019;43:121, Am J Surg Pathol 2020;44:943, Mod Pathol 2022;35:344). The main differential diagnosis for EVT includes oncocytoma and chromophobe renal cell carcinoma. However, other entities to consider on the differential are TFE3 rearranged renal cell carcinoma, TFEB altered renal cell carcinoma, eosinophilic solid and cystic renal cell carcinoma, succinate dehydrogenase deficient renal cell carcinoma, fumarate hydratase deficient renal cell carcinoma and epithelioid angiomyolipoma (Adv Anat Pathol 2021;28:251).
Test question answer:
A. EVTs are associated with somatic mutations in the mTOR pathway genes (TSC1, TSC2 or MTOR). EVTs are associated with somatic (not germline) mutations / biallelic losses in one of the mTOR pathway genes. Answer B is incorrect because solid / cystic architecture and diffuse immunoreactivity for CK20 are features of eosinophilic solid and cystic renal cell carcinoma. Answer C is incorrect because sickle cell trait is associated with SMARCB1 deficient renal medullary carcinoma. Answer D is incorrect because low grade oncocytic tumors are positive for CK7 and negative for CD117.
All cases are archived on our website. To view them sorted by case number, diagnosis or category, visit our main Case of the Month page. To subscribe or unsubscribe to Case of the Month or our other email lists, click here.
Thanks to Dr. Alcino Pires Gama and Dr. Bonnie Choy, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA for contributing this case and discussion and to Dr. Maria Tretiakova, University of Washington, Seattle, Washington, USA for reviewing the discussion.
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(1) The Directory at pathologyoutlines.com/directory now has a search feature by status: staff, trainee, retired, deceased, unspecified. We invite you to add or update your Directory profile to educate pathologists with your favorite image, words of wisdom, secrets of success or information about your research interests.
(2) Make sure to read our Curing Cancer Network October newsletter here. It includes information about Dr. Pernick's Cancer Precursor project findings to date. You can also read the full summary here.
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Visit and follow our Blog to see recent updates to the website.
Case of the Month #544
Clinical history:
A 56 year old patient with a 4.5 cm right renal mass underwent a partial nephrectomy.
Microscopic images:
What is your diagnosis?
Click here for diagnosis, test question and discussion:
Diagnosis: Eosinophilic vacuolated tumor
Test question (answer at the end):
Which of the following is true about eosinophilic vacuolated tumor (EVT)?
- EVTs are associated with somatic mutations in the mTOR pathway genes (TSC1, TSC2 or MTOR)
- EVTs have solid / cystic architecture and diffuse immunoreactivity for CK20
- EVTs occur predominantly in patients with sickle cell trait
- Unlike oncocytomas, EVTs are consistently strongly positive for CK7 and negative for CD117
Stains:
CK7
CD117
CD10
Cathepsin K
HMB45
Discussion:
In the 5th edition of the WHO Classification of Tumors, eosinophilic vacuolated tumor (EVT) is categorized under other oncocytic tumors of the kidney, a heterogeneous group of oncocytic tumors that are not classifiable as oncocytoma, chromophobe renal cell carcinoma (RCC) or other eosinophilic entities (WHO Classification of Tumours Editorial Board: Urinary and Male Genital Tumours, 5th Edition, 2022). EVTs typically present in adults of a broad age range. While almost all of the cases are sporadic, it has been reported in a patient with tuberous sclerosis complex (Histopathology 2019;75:440). Relatively limited follow up has not found evidence of recurrence or metastatic potential following resections of EVTs (Virchows Arch 2018;473:725, Mod Pathol 2022;35:344).
The tumors are well circumscribed but unencapsulated, with an average tumor size of 4.3 cm (Mod Pathol 2022;35:344). Histologically, EVTs have nested to solid growth with focal tubulocystic features, composed of eosinophilic cells with large intracytoplasmic vacuoles and prominent nucleoli, imparting a high grade appearance (Virchows Arch 2018;473:725, Am J Surg Pathol 2019;43:121, Mod Pathol 2022;35:344). Entrapped renal tubules and large vessels can be found at the periphery.
Immunohistochemically, EVTs are positive for PAX8, cathepsin K, CD117, CD10, SDH (retained), and FH (retained), while negative for CK7 (except rare cells), CK20, MelanA, HMB45 and TFE3 (Virchows Arch 2018;473:725, Am J Surg Pathol 2019;43:121, Mod Pathol 2022;35:344). EVTs are associated with somatic biallelic mutations in mTOR pathway genes (TSC1, TSC2 or MTOR) (Am J Surg Pathol 2019;43:121, Am J Surg Pathol 2020;44:943, Mod Pathol 2022;35:344). The main differential diagnosis for EVT includes oncocytoma and chromophobe renal cell carcinoma. However, other entities to consider on the differential are TFE3 rearranged renal cell carcinoma, TFEB altered renal cell carcinoma, eosinophilic solid and cystic renal cell carcinoma, succinate dehydrogenase deficient renal cell carcinoma, fumarate hydratase deficient renal cell carcinoma and epithelioid angiomyolipoma (Adv Anat Pathol 2021;28:251).
Test question answer:
A. EVTs are associated with somatic mutations in the mTOR pathway genes (TSC1, TSC2 or MTOR). EVTs are associated with somatic (not germline) mutations / biallelic losses in one of the mTOR pathway genes. Answer B is incorrect because solid / cystic architecture and diffuse immunoreactivity for CK20 are features of eosinophilic solid and cystic renal cell carcinoma. Answer C is incorrect because sickle cell trait is associated with SMARCB1 deficient renal medullary carcinoma. Answer D is incorrect because low grade oncocytic tumors are positive for CK7 and negative for CD117.
