Small Renal Mass—To Biopsy or Not? The Role of Biopsy in Evaluation

Histologic Diagnosis of Renal Mass Biopsy

CONTEXT.—

Core biopsy has been increasingly used for clinical decision-making in the management of patients with renal masses. The sensitivity and specificity of histologic diagnoses of renal mass biopsies depend on many factors such as adequate sampling and tissue processing, diagnostic skill and experience, and appropriate use of ancillary techniques.

OBJECTIVE.—

To review the indications, emphasize the importance of obtaining adequate diagnostic material, and introduce a general diagnostic approach, in conjunction with immunohistochemistry, in diagnosis of renal mass biopsies.

DATA SOURCES.—

Literature review and personal experiences in daily practice and consultation diagnosis of renal masses in a large tertiary medical center.

CONCLUSIONS.—

For renal mass biopsies, it is critical to obtain adequate diagnostic material and establish a standard laboratory procedure in working with small biopsy specimens. The key for the diagnosis is to be familiar with different tumor entities with characteristic morphology and to understand the wide spectrum of tumor heterogeneity. By developing a systematic approach, one can categorize the tumor and create a sensible differential diagnosis based on the growth pattern and cellular morphology. Immunohistochemistry is particularly helpful for renal mass biopsy diagnosis in selected situations.

Surgical histopathology for suspected oncocytoma on renal mass biopsy: a systematic review and meta-analysis

To estimate the proportion of oncocytic renal neoplasms diagnosed on renal mass biopsy (RMB) confirmed on surgical pathology, a systematic review of MEDLINE, Embase, and the Cochrane databases (1997 to 1 July 2016) was conducted quantifying all cases of reported oncocytic renal neoplasms on RMB suggestive of an oncocytoma. In addition, institutional data was assessed to identify additional cases. Concordance with surgical histopathology (positive predictive value [PPV]) was evaluated for patients undergoing surgery by performing a meta-analysis. In all, 10 RMB series, including institutional data, were included in the meta-analysis with 205 RMBs identifying oncocytic renal neoplasms and 46 (22.4%) proceeding to surgery. One additional study identified two neoplasms not captured by the primary RMB series for a total of 48 unique lesions included in the analysis. Surgical pathology showed oncocytoma (64.6%), chromophobe renal cell carcinoma (RCC; 12.5%), other RCC (12.5%), hybrid oncocytic/chromophobe tumour (6.3%), and other benign lesions (4.2%). PPV of oncocytoma on RMB was 67% (95% confidence interval 34-94%) with significant heterogeneity between studies (I² = 71.8%, P < 0.01). Risk of bias was judged to be low for four of the 10 series. Confidently diagnosing a localised renal mass as a benign lesion, such as an oncocytoma, has implications for the ultimate management strategy a patient will undergo. RMB was found to be unreliable in confidently diagnosing a localised renal mass as an oncocytoma, with one in four found to be RCC on surgical pathology. Patients and physicians should be aware of the uncertainty in diagnosis when considering management strategies.

A Systematic Review of Research Gaps in the Evaluation and Management of Localized Renal Masses

The management of clinically localized renal masses suspicious for renal cell carcinoma varies, partially because of gaps in the evidence base. We conducted a systematic review to summarize research gaps for the evaluation of composite models for predicting malignancy; use of percutaneous renal sampling for diagnosis; and comparative effectiveness of surgery, thermal ablation, and active surveillance. A total of 147 studies, published in 150 articles, were identified. To promote improved patient care and health outcomes, we recommend incorporation of emerging biomarkers into validated composite models, standardization of biopsy protocols, standard reporting of clinical stage, and performance of prospective studies with objective selection criteria.

Isolated brain metastasis from a small renal mass

The identification of small renal masses is increasing. Active surveillance is a guideline-approved management strategy for select patients with small renal masses. Metastases during the observation of small renal masses are uncommon, and no cases of brain metastasis have been reported. We report the case of a 73-year-old man who presented with tonic-clonic seizures as the result of a brain metastasis from a small renal mass (3.5 cm in maximal dimension). Treatment with whole brain radiotherapy was undertaken successfully. The patient will undergo surveillance with consideration for systemic therapy at the time of progression.