Renal Neoplasms with Predominant Oncocytic Features: Findings of 84 Fine Needle Aspiration Biopsies (FNAB) Specimens from a Single Institution

Abstract

s S27 Results: The primary source of UC included urinary bladder (26 patients), renal pelvis (4) and no known primary (2). The histologic findings were: Invasive high-grade UC (26 cases; 16 cases with muscularis propria invasion) invasive low-grade UC (1) and no histopathological details available (5). The metastatic sites included: Lymph nodes (13), Lung (4), Liver (4), Pleural/ pericardial fluid (4), Soft tissues (4), Bone (2) and Adrenal (1). There was no obvious correlation with the pathologic findings (depth of invasion) and the clinical presentation (time interval from diagnosis to metastasis that ranged from 1 month to 3 years; or sites of metastasis). In 28 cases; the morphology was fairly distinctive showing loosely cohesive groups of cells with usually numerous single cells with at least moderate “squamoid” cytoplasm, occasional cytoplasmic vacuolization, cytoplasmic tails and stellate cells with tissue culture cytoplasm. The nuclei showed uniform chromatin, usually small indistinct nucleoli and occasional intranuclear inclusions. The nuclei were uniform with occasional binucleate forms with scattered/ random markedly atypical nuclei noted occasionally. In 4 cases, the tumor cells were high-grade with cytologic and architectural features reminiscent of adenocarcinoma. IHC stains (performed in 16 cases) showed CK-7+/CK-20+ profile in 7/11 cases and CK7+/CK-20 negative in 4/11cases. CK34BE12 and p63 were co-expressed in all 7 cases in which those stains were performed. Conclusions: 1. Metastasis from UC can involve a wide range of locations including unusual sites such as soft tissues and body fluids. 2. The presence of loosely cohesive groups of tumor cells with squamoid and tissue culture type cytoplasm should raise the possibility of MUC in the differential diagnosis. 3. In a case of suspected MUC, a panel of commonly utilized antibodies CK-7, CK-20, CK34BE12 and p63 can help support the diagnosis. 4. The combination of above described morphology and IHC panel can help support or establish diagnosis of MUC as a cytologic diagnosis in difficult cases.