Clear cell sarcoma of kidney

Case contributed by Dr Brian Gilcrease-Garcia

Presentation

Palpable abdominal mass

Patient Data

Age: 9 months
Gender: Male
Ultrasound

Large heterogenous abdominal mass exerting mass effect on both intraperitoneal and retroperitoneal structures. Although origin cannot be confidently determined, the lesion appears to be centered on right renal artery (which shows patent flow on spectral Doppler), suggesting a primary renal tumor.

Recommend further characterization by CT.

CT
  • large central mass massively expands right kidney, with a small amount of normal renal parenchyma is apparent on the periphery (claw sign)
    • large central hypodense areas suggest necrosis
    • no evidence of extra-renal invasion (limited assessment)
  • pronounced mass effect on all adjacent structures
    • compressed inferior vena cava, bowel
    • mild upward displacement of liver
    • small umbilical hernia
  • no evidence of metastatic disease

(Presumably) on the basis of epidemiology, presumptive diagnosis of Wilms tumor was made. Patient was managed by initiation of neoadjuvant chemotherapy...

CT

CT abdomen/pelvis after 6 weeks chemo

  • interval enlargement of the mass, best appreciated by...
    • further extension across midline (axial images)
    • increased mass effect on liver (coronal image)
    • decreased, only thin crescent, of normal right kidney parenchyma remaining
  • there remains no evidence of extra-renal invasion or metastasis

Surgical pathology

Impression

Kidney and adrenal, right, radical nephrectomy

  • Clear cell sarcoma of kidney, 19.8 cm
  • tumors invades through capsule into perinephric fat and renal sinus lymphvascular spaces (stage ii)
  • renal vein, ureteric and parenchymal resection margins free of tumor

Lymph nodes, paraaortic, excision

  • No evidence of malignancy in two lymph nodes

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Microscopic description

  • sections of renal mass show a monomorphic population of rounded cells arranged in a diffuse-to-corded pattern consisting of ovoid-to-round nuclei, vesicular chromatin, inconspicuous nucleoli. Cytoplasm is moderate, and mostly clear-to-eosinophilic. A delicate arborizing-to-parallel vascular network separates groups of tumor cells
  • tumor-renal parenchymal interface is well-demarcated, focally infiltrating without pseudocapsule
  • limited panel of immunostains show WT-1 to be negative in the tumor cells. INI-1 is retained. Cytokeratin fails to identify tubular cell rests and is negative
  • overall, histomorphology is consistent with a clear cell sarcoma of the kidney, supported by its immunophenotype. By invasion through the capsule into the perinephric fat, as well as by invasion into the renal sinus lymphovascular spaces, this is stage II. Tumor is not seen present at ink, on multiple sections, therefore, presumed to be completely resected

Gross description

  • first specimen labeled "right kidney and adrenal" consists of a previously inked and bivalved kidney and adrenal gland
  • adrenal gland measures 6.5 x 1.5 x 0.1 cm. The gland is compressed on the surface of the kidney, but tumor does not grossly appear to invade it
  • [right kidney] external surface is intact and glistening and not grossly disrupted. Cut surface appears heterogenous with tan-pink area mixed with regions of yellow-white friable parenchyma with regions of necrosis. Overall architecture is lobulated with regions of white-tan tissue having a glistening, mucoid appearance
  •  a green cassette labeled "ureter margin" and holds a tan-brown fragment of tissue measuring 1.6 x 0.6 x 0.7 cm and is compressed at one end

Case Discussion

This case highlights the ambiguity of solid pediatric renal masses, as well as some important points regarding the management of Wilms tumor.

By imaging appearance, solid pediatric renal tumors often appear similar and cannot be distinguished with high specificity. By epidemiology, a diagnosis of Wilms tumor is reasonable, as they account for ~90% of pediatric renal masses. However, uncommon lesions should be considered if...

  • aggressive appearance (large amounts of necrosis)
  • atypical age range (Wilms tumor peak incidence is 3 years old, never in newborns)
  • other suggestive characteristic

Regarding management of Wilms tumor, there are two major entities which advocate different approaches:

  • National Wilms Tumor Study / Children's Oncology Group (COG) - North America
    • early surgical resection and staging, followed by chemotherapy
  • International Society of Pediatric Oncology (SIOP) - Europe, South America
    • neoadjuvant chemotherapy, followed by surgical resection and diagnostic confirmation

Although treatment outcomes are felt to be similar, one risk of the SIOP-type approach is the misdiagnosis of benign or malignant lesions based on imaging, since histopathologic confirmation may be delayed until the time of resection.

Due to rarity, there is no standard treatment for either rhabdoid tumor or clear cell sarcoma of the kidney 2.

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Case information

rID: 60647
Published: 12th Aug 2018
Last edited: 13th Aug 2018
Inclusion in quiz mode: Included
Institution: Washington University in Saint Louis

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