Weekly Case

Title : Case 683

Age / Sex : 39 / M

Chief complaint : Rt. knee pain

What is your diagnosis?

Two weeks later, you can see the final diagonosis with a brief discussion of this case (Please submit only one answer).

Courtesy : 
채희동, Hee-Dong Chae, 서울대학교병원, Seoul National University Hospital



Brown tumor (Primary hyperparathyroidism)



A skyline view of the right knee shows a well-defined osteolytic lesion in the patella. Axial T2-weighted SPIR image shows a multiloculated cystic lesion with a fluid-fluid level in the patella. The cystic lesion demonstrates peripheral and septal wall enhancement on a sagittal contrast-enhanced T1-weighted image, and there is no solidly enhancing component. There are also multiple cystic bone lesions in the pelvis and both femurs on the coronal reformatted CT image. Several subchondral bone erosions are visible in both sacroiliac joints. The patient's serum calcium level was 13.1 mg/dl (ref 8.8~10.5 mg/dl), and phosphorus level was 1.7 mg/dl (2.5~4.5 mg/dl).


Differential Diagnosis:

Giant cell tumor

Aneurysmal bone cyst



Brown tumor is a nonneoplastic lesion that occurs as a manifestation of hyperparathyroidism. It is also known as osteitis fibrosa cystica or osteoclastoma. The overproduction of parathyroid hormone leads to the increased osteoclastic resorption of bone. Localized areas of severe bone loss are filled with granulation tissue and vascularized fibrous tissue with hemosiderin deposition, resulting in “brown tumor”. Brown tumors usually resolve with the treatment of hyperparathyroidism, and local treatment of the tumor itself is usually not necessary.

Brown tumors tend to occur more frequently in patients with primary hyperparathyroidism (3 %) than those with secondary hyperparathyroidism (1.5-1.7 %). However, the overall incidence of secondary hyperparathyroidism is much more higher than primary hyperparathyroidism.

Brown tumors occur throughout the entire skeleton. Commonly involved sites include small tubular bones of hands, skull, pelvis, clavicle, rib, spine, and femur.

Brown tumors occur as well-defined, geographical osteolytic lesions that are centrally located, and may be slightly expansile. Brown tumors can exhibit either a solid or cystic nature or a mixture of the two. Solid portions have been reported to show isointensity to hypointensity on T1-weighted and T2-weighted images, and cystic portions may exhibit fluid-fluid levels.



Kang HS, Ahn JM, Kang Y. Oncologic Imaging: Bone Tumors: Springer; 2017.

Correct Answer
Total applicants 33 Correct answers 20
Name Institution
장민영 국민건강보험공단 일산병원, 전문의
여현정 전문의
여현정 전문의
김기욱 전문의
이동규 경인지방병무청, 전문의
이진영 전문의
이혜란 전문의
고영선 충주중앙병원, 전문의
전인환 전문의
권기언 서울아산병원, 전문의
김동언 서울아산병원, 전문의
문경일 전남대학교병원, 전공의
이규정 국군대전병원, 전문의
이현규 전문의
김영미 삼성창원병원, 전문의
김성진 365병원, 전문의
이승보 서울아산병원, 전문의
백승진 분당차병원, 전공의
심상우 서울아산병원, 전문의
김동찬 단국대학교 병원, 전공의
Semi-Correct Answer
Total applicants 33 Semi-Correct answers 7
최은지 전공의
조영민 전문의
임윤진 단국대학교병원, 전공의
윤선근 전공의
강지희 전문의
김동수 전공의
김현진 서울성모병원, 전공의