PMC7180427_01
Abdominal CT scan showing symmetrical, bilateral perirenal rind-like lesions (arrows) measuring 2.5 cm in thickness, so-called hairy kidney sign.
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After a thorough clinical history yielded negative results, the patient was sent for an abdominal pelvic CT scan where the identification of rind-like bilateral perirenal masses by the radiologist resulted in the presumptive diagnosis of Erdheim-Chester disease (Figure 1).
Needle biopsy of perirenal lesion showing (a) collision tumor of ECD with low grade B cell lymphoma; (b) foamy histiocytes, fibrous stroma, and scattered inflammatory cells of ECD; (c) foamy histiocytes admixed with small monomorphous lymphocytes; and (d) small lymphocytic lymphoma.
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An atypical lymphoid infiltrate with interstitial and nodular architecture accompanied the histiocytosis (Figure 2).
Immunohistochemical findings of perirenal mass. (a) CD79a, (b) CD3, (c) CD5, (d) CD68. (e) Flow cytometric findings of perirenal mass typical of SLL (CD19+, Kappa+, CD5+, CD23+, CD10-, and FMC7-).
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A sample of the biopsy was sent for flow cytometric assessment and showed monoclonal B lymphocytes with kappa light chain restriction and typical SLL phenotype (Figure 3).