Oncocytic neoplasms are growths or tumors composed of specialized cells called oncocytes. A primary concern for patients is whether these growths are cancerous, as oncocytic neoplasms can be either benign (non-cancerous) or malignant (cancerous). This article provides information on oncocytic neoplasms and addresses the distinction between their benign and malignant forms.
What Are Oncocytic Neoplasms?
Oncocytic neoplasms are characterized by the presence of oncocytes, specialized cells with a distinctive appearance. These cells are notably enlarged and have a granular, eosinophilic (pink-staining) cytoplasm when viewed under a microscope. This granular appearance is due to an unusually high number of mitochondria, the “powerhouses” of the cell, which accumulate within the cytoplasm. The term “oncocyte” derives from a Greek word meaning “swelling” or “mass,” reflecting their enlarged nature.
Oncocytes can develop in various organs throughout the body, including endocrine glands. They are commonly found in the thyroid, kidney, and salivary glands, but can also appear in other locations like the adrenal glands.
Distinguishing Benign from Malignant Types
Oncocytic neoplasms can be either benign (non-cancerous) or malignant (cancerous). Benign oncocytic neoplasms are often called oncocytomas, while malignant ones are typically called oncocytic carcinomas. Distinguishing between these two types is challenging, as both can share similar microscopic features, making visual differentiation difficult even for experienced pathologists.
The key factor determining if an oncocytic neoplasm is benign or malignant is its biological behavior. A growth is considered malignant if its cells demonstrate invasive characteristics, such as growing into surrounding tissues or spreading through blood vessels. Conversely, a growth is considered benign if it is confined and does not exhibit such aggressive behavior. Therefore, the distinction relies on evidence of invasive potential, not just the appearance of the cells.
How Oncocytic Neoplasms Are Diagnosed
The diagnostic process for oncocytic neoplasms typically begins with imaging studies like ultrasound, CT scans, or MRI. These techniques help locate the growth and provide information about its size and other features. However, imaging alone often cannot definitively determine if a growth is benign or malignant, as oncocytic neoplasms can appear similar to other tumor types.
Following imaging, a biopsy is usually performed to obtain tissue for examination, often through fine needle aspiration or a core biopsy. Pathologists then examine the tissue under a microscope, looking for oncocytic cells and specific features that indicate malignancy. These features can include cellular atypia (abnormal cell appearance), increased mitotic activity (rapid cell division), and evidence of capsular or vascular invasion, where cells breach surrounding tissue or blood vessels.
In some instances, a definitive diagnosis of benign versus malignant cannot be made solely from a biopsy sample. This can occur because a small biopsy might not capture areas showing invasion. In such cases, a conclusive diagnosis may only be possible after surgical removal of the entire growth, allowing for a comprehensive pathological analysis. Immunohistochemical staining, which uses antibodies to identify specific proteins, can also assist pathologists in differentiating between benign and malignant forms.
General Treatment Approaches and Prognosis
Treatment strategies for oncocytic neoplasms vary based on whether they are benign or malignant, their location, and size. For benign oncocytomas, active surveillance (watchful waiting) may be an option, particularly if the growth is small and not causing symptoms. If the benign growth is large or causes symptoms, surgical removal might be recommended.
For malignant oncocytic carcinomas, surgical removal of the tumor is typically the primary treatment. The extent of surgery depends on factors like tumor size and whether it has spread. For example, in thyroid oncocytic carcinoma, total thyroidectomy is often recommended for larger tumors or those showing invasive characteristics. Prognosis for oncocytic carcinomas can vary widely, influenced by the affected organ, the cancer’s stage, and whether it has metastasized. While some oncocytic carcinomas can exhibit aggressive behavior, many are slow-growing and have a favorable prognosis, particularly when detected and treated early.