What is the management approach for oncocytic neoplasms (tumors) in various organs?

Management of Oncocytic Neoplasms

For renal oncocytic neoplasms with borderline features that cannot be definitively classified as oncocytoma or chromophobe RCC, use the term "oncocytic renal neoplasm of low malignant potential, not further classified" and manage with active surveillance using the same protocol as low-risk renal cell carcinoma. 1

Diagnostic Approach for Renal Oncocytic Neoplasms

Strict Classification Criteria

• Apply very strict definitions to distinguish prototypical oncocytoma from chromophobe RCC (ChRCC), as these entities have overlapping morphologic features 1
• Exclude well-described mimics including epithelioid angiomyolipoma and succinate dehydrogenase (SDH)-deficient RCC before settling on a borderline diagnosis 1
• Reserve the term "hybrid oncocytic tumor" exclusively for hereditary cases (such as Birt-Hogg-Dubé syndrome) that show a characteristic "checkerboard" mosaic pattern with scattered clear cells 1

Biopsy Considerations and Limitations

• Exercise caution when diagnosing oncocytoma on core biopsy due to regional tumor heterogeneity—ChRCC and other subtypes may have foci indistinguishable from oncocytoma 1
• For biopsies showing oncocytoma morphology, consider reporting as "oncocytic renal neoplasm" with a comment: "If this biopsy sample is representative of the entire lesion, the appearances would be consistent with an oncocytoma" 1
• Perform pretreatment diagnostic biopsy for all patients undergoing ablation procedures to refine post-ablative follow-up and prevent empirically labeling patients as having renal cancer 1

Active Surveillance Protocol

Imaging Schedule

• Obtain cross-sectional abdominal imaging (CT or MRI) at 6 months from surveillance initiation to establish the tumor's growth pattern 1, 2
• Continue imaging (ultrasound, CT, or MRI) at least annually thereafter 1, 2
• Measurement variability of 3.1 mm inter-observer or 2.3 mm intra-observer should not be attributed to tumor growth unless persistent increases occur over two or more interval exams 1, 2

Rationale for Surveillance Intensity

RCC, oncocytoma, oncocytic neoplasms, and indeterminate histologies should all be followed with identical imaging protocols as untreated low-risk (cT1, N0, Nx) RCC for three critical reasons: 1

• Oncocytomas, while benign, can exhibit substantial growth threatening the renal unit 1
• Differentiation between oncocytoma and chromophobe RCC on percutaneous biopsy presents a diagnostic dilemma 1
• Chromophobe RCC has a more indolent natural history, allowing for lower intensity surveillance 1

Chest Imaging Requirements

• Perform annual chest X-ray for patients with biopsy-proven RCC or tumors with oncocytic features to assess for pulmonary metastases 1, 2
• For biopsy-proven high-grade RCC or neoplasms displaying rapid interval growth, chest imaging may be performed annually or more frequently based on clinical behavior 1
• Chest imaging may be omitted only for biopsy-proven benign neoplasms 1

Prognosis and Risk Stratification

Low Metastatic Risk

• Collective experience from large renal cancer centers demonstrates that "difficult to classify" oncocytic tumors have exceedingly low risk for developing metastatic disease 1
• The term "oncocytic renal neoplasm of low malignant potential, not further classified" represents primarily a clinical management category that likely includes a heterogeneous group of renal neoplasms 1

Limited Role of Molecular Testing

• At present, there is no compelling evidence that immunophenotypic or molecular testing aids in predicting biologic risk for tumors in the oncocytic spectrum 1

Management of Oncocytic Neoplasms in Other Organs

Adrenal Oncocytic Neoplasms

• Adrenal oncocytic neoplasms are extremely rare, usually nonfunctional (83% are incidental findings), and most commonly benign 3
• Adrenalectomy is the mainstay of therapy, increasingly performed laparoscopically 3
• CT and MRI cannot differentiate benign from malignant oncocytic neoplasms in the adrenal gland 3
• Classify adrenal oncocytic neoplasms using the Lin-Weiss-Bisceglia system to determine biological behavior as benign, borderline malignant potential, or malignant 4
• Prognosis is good for benign tumors, while adrenocortical oncocytic carcinoma has poor 5-year survival 3

Thyroid Oncocytic Cell Tumors

• Tumor size greater than 3.0-4.0 cm significantly predicts malignancy in thyroid oncocytic cell tumors 5
• Tumor multifocality, microfollicular features, and severe cytological atypia are significantly related to malignancy 5
• Total thyroidectomy is strongly recommended as initial treatment for larger thyroid oncocytic tumors with microfollicular features and severe cytological atypia due to more aggressive biological behavior 5

Pancreatic Oncocytic Neoplasms

• Oncocytic carcinomas can rarely arise in association with intraductal papillary mucinous neoplasms (IPMNs) 1
• These should be recognized and reported separately from other invasive carcinoma types 1

Critical Pitfalls to Avoid

• Do not omit chest imaging for oncocytic neoplasms—despite potential benign histology, follow the same surveillance protocol as low-risk RCC due to diagnostic uncertainty with chromophobe RCC 1, 2
• Do not use tumor size measurements alone without considering measurement variability between observers 1, 2
• Do not diagnose oncocytoma definitively on core biopsy without acknowledging sampling limitations and regional heterogeneity 1
• Do not perform ablation or conservative therapy without pretreatment biopsy, as this prevents appropriate risk stratification 1