Pathologically Benign Lymph Nodes Can Mimic Malignancy on Imaging in Patients With Angiomatoid Fibrous Histiocytoma.

Background: Angiomatoid fibrous histiocytoma (AFH) is a rare soft tissue neoplasm, and its rarity makes studying it difficult. We found that several of our patients with AFH presented with radiologically suspicious local lymph nodes that were sampled because of their imaging characteristics, but the nodes proved to be benign on pathologic evaluation. Although the frequency of this finding is unknown, it seems important for orthopaedic oncologists who care for patients with AFH to know whether suspicious-appearing associated nodes in these patients warrant aggressive management.

Questions/purposes: (1) How often do patients with newly diagnosed AFH present with radiologically suspicious lymph nodes? (2) How often are the radiologically suspicious nodes malignant on pathologic evaluation?

Methods: In this retrospective, Health Insurance Portability and Accountability Act-compliant study, we used a hospital database to identify all 54 patients treated at our hospital for AFH between 1993 and 2016. This study was performed with institutional review board waiver. All of the patients were considered potentially eligible for analysis. Of the patients, 19 (35%) had pretherapy imaging; during the period in question, pretherapy imaging generally was obtained when there was uncertainty regarding extent of disease. All patients who had imaging underwent MRI, and four also had fluorodeoxyglucose positron emission tomography (FDG PET/CT). Imaging reports were reviewed to identify which patients had nodes that were called suspicious in the reports. All patients with nodes described as suspicious on imaging underwent subsequent pathologic analysis for the presence or absence of metastatic AFH cells in the node.

Results: Seven of 19 patients with pretherapy imaging had local lymph nodes called suspicious for nodal metastases. Pathologic analysis of these nodes showed they were malignant in only one patient, whereas six patients had nodes that were histologically benign despite suspicious imaging findings. Benign nodes measured as much as 3.2 × 1.8 cm on MRI and showed maximum standardized uptake values up to 10.9 on FDG PET/CT.

Conclusions: Patients with newly diagnosed AFH present with benign lymph nodes that are mistaken for malignancy on imaging. Orthopaedic surgeons and radiologists should be aware of this finding in patients with AFH. Less-invasive management of suspicious nodes, such as image-guided biopsy, may be preferable to nodal resections, as this will help decrease the aggressiveness of surgery for patients with newly diagnosed AFH.

Level Of Evidence: Level IV, diagnostic study.