Case of the Week

2020-15 / APRIL 12 (CONTRIBUTOR: DANIEL H. RUSSELL)

A 65 year old male was found to have a 2.6 cm renal mass. A robotic partial nephrectomy was performed. Special stains for microorganisms were negative.

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3 photo(s) Updated on: April 04, 2020

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Quiz

1. What is the correct diagnosis?

a. Collision of granulomatous disease with clear cell renal cell carcinoma.

b. Clear cell renal cell carcinoma.

c. Renal cell carcinoma, unclassified type.

d. Granulomatous pyelonephritis.

e. Sarcoidosis

Histologic evaluation shows a clear cell neoplasm with acinar growth and “chicken wire” type vasculature, as well as admixed areas of scar and non-necrotizing granulomata. The nuclei are round and dark, while some foci contain nuclei with open chromatin and conspicuous eosinophilic nucleoli identifiable at 400x magnification. Non-necrotizing sarcoidal-like granulomata (SLG) are present in both a peritumoral and intratumoral distribution, and were accompanied by mixed inflammation of varying intensity. Special stains for microorganisms (Gram, PAS fungal, GMS, and Kinyoun) were negative, and a review of the patient’s past medical history was unremarkable for connective tissue disease, pertinent travel history, or pulmonary symptoms. The diagnosis is clear cell renal cell carcinoma, ISUP (International Society of Urological Pathologists) grade 2.

There have been a handful of previously reported cases in the literature of SLG occurring in association with RCC. Of those previously reported, none were associated with infection and only 3 had a history of connective tissue disease, all sarcoidosis. The histotypes of reported cases include 23 clear cell RCCs, 1 clear cell RCC with sarcomatoid features, 1 clear cell papillary RCC, and 1 chromophobe RCC. In 3 of the cases, SLG were also identified in regional lymph nodes draining tumor, while SLG present in lung metastases as well as perinephric fat have also been reported. SLG are not infrequently found in association with malignancy, albeit uncommonly in kidney cancer. The exact stimulus for granuloma formation in RCC is unknown, with some evidence that the antigenic trigger may be intracytoplasmic glycogen which may partially explain the predominance of reported cases in tumor histotypes containing intracytoplasmic glycogen (25/26 reported cases).

The prognostic significance of SLG in RCC is unsettled and somewhat complicated by the relative rarity of its occurrence and the paucity of data therein.

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