CORRInsights®: Pathologically Benign Lymph Nodes Can Mimic Malignancy on Imaging in Patients With Angiomatoid Fibrous Histiocytoma

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Some soft-tissue tumors are associated with a low potential for lymphonodular metastasis. Myxoinflammatory fibroblastic sarcomas and plexiform fibrohistiocytic tumors [4, 9] are two such diseases; angiomatoid fibrous histiocytoma (AFH) is another. It is important to recognize that although nodal metastases are rare, they do occur, and it is this potential that makes diagnosis and treatment of patients with AFH so challenging.
For patients with enlarged lymph nodes, surgeons, oncologists, radiologists, and pathologists considering resection must weigh the risk of overtreatment (since most of these patients will not have nodal metastases) against the risk of undertreatment (as a few patients will develop such metastases and become incurable [12]). By contrast, although lymph node dissection is a rather straightforward procedure, it still can cause perioperative morbidity, and axillary and inguinal lymph node dissection may lead to chronic lymphedema, recurrent erysipelas, and poor quality of life [10]. Therefore, unnecessary lymph node dissection should be avoided.
The challenge for clinicians treating malignancies is finding the right balance of therapy. Common tumors such as breast or colonic cancers often accumulate large patient numbers for potential studies, making it easier to establish guidelines for the statistically best therapy. But because AFH is a rare disease, clinicians must make a decision on an individual basis, with little evidence to help guide them. The current study by Ulaner and colleagues is important because it gives a rough estimation of how often lymph node metastases occur and how they might be detected.
How to properly detect nodal metastases has long been under investigation [3, 13], leading to a sensitivity and specificity around 75% for both CT and MRI. The main criterion of malignancy in CT and MRI is the size of the lymph node; if the diameter in the short axis exceeds a certain cut-off, the lymph node will likely be suspected of malignancy. In fludeoxyglucose-positron emission tomography (FDG-PET) scans, elevated uptake values are a sign of malignancy [6]. FDG-PET scans are also useful for staging other sarcomas [11]. However, AFH has the peculiar property of causing lymphadenopathy and systemic symptoms likely due to the production of cytokines by neoplastic cells [5]. This reactive lymph node activation may cause an elevated FDG uptake, potentially leading to the discovery of suspicious, but benign, lymph nodes on both MRI and FDG-PET/CT imaging.
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