First Reported Case of Nodular Fasciitis with Intraosseous Patellar Involvement: A Case Report.
- 1Department of Orthopedic Surgery, Section of Orthopedic Oncology, Rush University Medical Center, Chicago, Illinois, United States of America.
- 2Department of Pathology, Rush University Medical Center, Chicago, Illinois, United States of America.
Abstract
Nodular fasciitis is a benign, self-limited myofibroblastic proliferation that most commonly arises in the superficial soft tissues of young adults. It is characterized by rapid growth and histologic features that can mimic sarcoma, often prompting concern for malignancy. Intra-articular nodular fasciitis is exceedingly rare, and involvement of bone is particularly unusual. The identification of recurrent ubiquitin-specific protease 6 (USP6) gene rearrangements has clarified the neoplastic nature of nodular fasciitis and provided a valuable molecular diagnostic tool, especially in atypical clinical or anatomic presentations. We report the first documented case of nodular fasciitis with intraosseous involvement of the patella. A 67-year-old man with a history of follicular lymphoma presented with a 6-month history of progressively worsening right anterior knee pain. Magnetic resonance imaging demonstrated a 2.1 × 1.3 × 1.9 cm heterogeneous subpatellar soft-tissue mass with internal nodularity, peripheral enhancement, and cortical erosion of the inferior patella. Given the patient's oncologic history and aggressive imaging features, the differential diagnosis included metastatic disease, tenosynovial giant cell tumor, synovial chondromatosis, and gouty arthritis. Image-guided biopsy revealed a hypercellular spindle cell proliferation in a myxoid stroma with extravasated erythrocytes and occasional giant cells, suggestive of nodular fasciitis; however, the intra-articular location and osseous involvement were highly atypical. Fluorescence in situ hybridization demonstrated a rearrangement of the USP6 gene, confirming the diagnosis. Due to persistent symptoms and bony involvement, the patient underwent surgical excision of the mass with curettage of the patella. Post-operatively, he experienced significant pain relief without complications. This case represents the first reported instance of nodular fasciitis with intraosseous involvement of the patella. It highlights the importance of considering nodular fasciitis in the differential diagnosis of intra-articular knee masses, even in older patients and in the presence of bone erosion. Molecular confirmation with USP6 testing is invaluable in establishing the diagnosis when clinical, radiographic, or histologic features are atypical. Surgical excision remains an effective treatment option for symptomatic lesions refractory to conservative management.
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BibTeX
@article{riley2026first,
title = {{First Reported Case of Nodular Fasciitis with Intraosseous Patellar Involvement: A Case Report.}},
author = {Dylan J Riley and Fernando O Gonzalez and Alan T Blank},
journal = {Journal of orthopaedic case reports},
year = {2026},
month = nov,
doi = {10.13107/jocr.2026.v16.i11.8426},
url = {https://europepmc.org/article/MED/42997184},
note = {CC BY-NC},
}
RIS
TY - JOUR
TI - First Reported Case of Nodular Fasciitis with Intraosseous Patellar Involvement: A Case Report.
AU - Dylan J Riley
AU - Fernando O Gonzalez
AU - Alan T Blank
PY - 2026
DA - 2026/11/01
JO - Journal of orthopaedic case reports
DO - 10.13107/jocr.2026.v16.i11.8426
UR - https://europepmc.org/article/MED/42997184
AB - Nodular fasciitis is a benign, self-limited myofibroblastic proliferation that most commonly arises in the superficial soft tissues of young adults. It is characterized by rapid growth and histologic features that can mimic sarcoma, often prompting concern for malignancy. Intra-articular nodular fasciitis is exceedingly rare, and involvement of bone is particularly unusual. The identification of recurrent ubiquitin-specific protease 6 (USP6) gene rearrangements has clarified the neoplastic nature of nodular fasciitis and provided a valuable molecular diagnostic tool, especially in atypical clinical or anatomic presentations. We report the first documented case of nodular fasciitis with intraosseous involvement of the patella. A 67-year-old man with a history of follicular lymphoma presented with a 6-month history of progressively worsening right anterior knee pain. Magnetic resonance imaging demonstrated a 2.1 × 1.3 × 1.9 cm heterogeneous subpatellar soft-tissue mass with internal nodularity, peripheral enhancement, and cortical erosion of the inferior patella. Given the patient's oncologic history and aggressive imaging features, the differential diagnosis included metastatic disease, tenosynovial giant cell tumor, synovial chondromatosis, and gouty arthritis. Image-guided biopsy revealed a hypercellular spindle cell proliferation in a myxoid stroma with extravasated erythrocytes and occasional giant cells, suggestive of nodular fasciitis; however, the intra-articular location and osseous involvement were highly atypical. Fluorescence in situ hybridization demonstrated a rearrangement of the USP6 gene, confirming the diagnosis. Due to persistent symptoms and bony involvement, the patient underwent surgical excision of the mass with curettage of the patella. Post-operatively, he experienced significant pain relief without complications. This case represents the first reported instance of nodular fasciitis with intraosseous involvement of the patella. It highlights the importance of considering nodular fasciitis in the differential diagnosis of intra-articular knee masses, even in older patients and in the presence of bone erosion. Molecular confirmation with USP6 testing is invaluable in establishing the diagnosis when clinical, radiographic, or histologic features are atypical. Surgical excision remains an effective treatment option for symptomatic lesions refractory to conservative management.
SN - 2250-0685
SN - 2321-3817
ER -