PAX8-Positive B-Cell Lymphoma in Adrenal Gland Masquerading as Metastatic Renal Cell Carcinoma.

Extranodal lymphomas involve adrenal glands as a mass lesion in 3% to 5% of cases as identified by imaging studies. Definitive diagnosis of the neoplasm is provided by morphological and immunophenotypical evaluation on limited tissue obtained by fine needle aspiration or core biopsy. We report a diagnostically challenging case that presented as masses involving adrenal gland and lung in the setting of a concurrent primary renal cell carcinoma. PAX8, a frequently used marker for renal cell carcinoma, was immunoreactive in the neoplastic cells of the adrenal mass, and thus highly suggestive for metastatic renal cell carcinoma. The neoplasm was eventually proven to represent PAX8-positive diffuse large B-cell lymphoma after extended immunohistochemical workup. This case of unusual presentation of synchronous renal cell carcinoma and adrenal lymphoma with overlapping PAX8 immunoreactivity serves as a potential diagnostic pitfall with significant clinical implications.