Cytomorphology of renal angiomyolipoma: performance and accuracy of touch preparation of core needle biopsy

INTRODUCTION

The recognition of renal angiomyolipoma (AML) can be challenging based on cytology preparations such as touch preparation (TP) of core needle biopsy (CNB) and fine needle aspiration. This study evaluated the cytologic features and performance of TP of CNB during rapid onsite evaluation (ROSE) of renal AML.

MATERIALS AND METHODS

A pathology database search was performed between 2000 and 2021 for renal CNB specimens with ROSE using TP that were primarily favored AML on preliminary impression and/or confirmed AML on CNB or subsequent resection.

RESULTS

Twenty confirmed AML were identified (90% female, median age 65.5 years). Sixteen (80%) were deemed adequate for diagnosis at the time of ROSE, and 9 of 16 (56%) had available onsite impression: AML was favored in 4 of 9 cases (44%). Examination of TP slides revealed spindle/epithelioid cells in 20 (100%), adipose tissue in 14 (70%), and blood vessels in 3 (15%). All AML cases were subsequently confirmed by immunohistochemistry. Additionally, 3 other cases with ROSE favoring AML revealed to be "renal parenchyma with fibrosis," clear cell papillary renal cell tumor and clear cell renal cell carcinoma.

CONCLUSIONS

Onsite evaluation of TP ensures adequate material for diagnosis in most renal AML. Spindle/epithelioid cells were the most common component seen on TP, followed by adipose tissue. Blood vessels were rarely seen. While the recognition of AML at ROSE can be challenging, proper evaluation is important in obtaining adequate diagnostic tissue. Correlation with CNB and utilization of immunohistochemistry are crucial for arriving at the diagnosis.

Renal Angiomyolipoma

The findings at ultrasonography (US), CT, and angiography in 13 patients with renal angiomyolipomas were compared with histologically determined proportions of fatty, myogenic, and vascular components. The angiomyolipoma was composed mainly of fat in 4 cases, half of fat in 2, mainly of myogenic tissue in 4, and was hemorrhagic in 3. US showed high echogenicity in 10 patients, while CT demonstrated attenuation values of fat in 3 tumors with mainly fat tissue but gave non-specific findings in the other cases. The angiographic findings were considered specific for angiomyolipoma in 2 out of 11 cases (18%). Low fat content and hemorrhagic areas caused diagnostic difficulties at both US and CT. The diagnostic algorithm for renal angiomyolipoma is discussed.

Fine-needle aspiration of renal angiomyolipoma: Cytological findings and diagnostic pitfalls in a series of five cases

Diagnosis of renal angiomyolipoma (AML) by fine-needle aspiration (FNA) may be difficult because cytological and radiological findings sometimes overlap with renal cell carcinoma (RCC) and liposarcoma. Five FNAs of AMLs were studied. Epithelioid and spindle stromal cells were arranged in loosely cohesive clusters and singly. The chromatin was evenly distributed and bland. Occasionally nuclear atypia was identified. Nuclei were oval to elongated, nucleoli were inconspicuous or absent, naked nuclei were present in three specimens, and intranuclear inclusions were present in two specimens. The cytoplasm was delicate and sometimes finely vacuolated. Adipose tissue was observed in two specimens. Thick-walled vessels, mitoses, and necrosis were absent. Corresponding surgical material showed typical features of AML. In FNA, bland chromatin and inconspicuous nucleoli distinguish renal AML from RCC and liposarcoma. Adipose tissue is not universally present. Cellular atypia in conjunction with overlapping radiological findings with RCC and liposarcoma are potential diagnostic pitfalls. Immunocytochemical (ICC) stains may elucidate the correct diagnosis.

Preoperative diagnosis of renal angiomyolipoma: fine needle aspiration cytology and immunocytochemical characterization

A preoperative diagnosis of renal angiomyolipoma (AML) is of great importance for a correct management of these patients with this tumor. In fact when the lesion is small and asymptomatic a conservative approach may be considered. We have evaluated the radiographic and fine needle aspiration cytology (FNAB) findings in 8 cases of AML. In 3 cases both radiology and cytology were suggestive of carcinoma and thus the patients underwent surgery. In one case both techniques suggested AML but surgery was performed because the lesion was large and symptomatic. In 4 cases where both radiology and cytology suggested AML no surgery was performed. Follow-up data are consistent with the benign nature of the lesions. The immunocytochemical analysis of the FNAB with a panel of antibodies including keratin, vimentin, actin and HMB-45 was indicative of AML in 7 of 8 cases, including 2 of the 3 cases misdiagnosed as carcinomas. The presence of HMB-45-positive perivascular epithelioid cells in the FNABs was the most significant finding. It is concluded that immunocytochemical analysis of FNAB with this monoclonal antibody panel can increase the accuracy of preoperative diagnosis of AML, and allow consideration of a conservative approach in selected cases.