Case Reports in Orthopedics / 2019 / Article / Tab 1

Case Report

An Unusual Case of Huge Tophaceous Pseudogout Mimicking as a Tumor-Like Lesion around the Ankle Joint: A Case Report and Literature Review

Table 1

Differential diagnosis for the patient in our case report and their distinguishing features.

Site of originMost common distributionRadiological appearanceHistological appearance

Tumoral pseudogoutPeriarticularTemporomandibular joint, perispinal tissues, joints of extremitiesRadiopaque soft tissue mass with varying densities of calcificationAmorphous calcium deposits with numerous refractile radiating rhomboid crystals, demonstrates positive birefringence on polarized microscopy
Tophaceous goutPeriarticular1st MTP joint, hands and feetJuxtaarticular punched out erosions with sclerotic marginsTophi—granulomatous inflammation with plenty of needle-shaped crystals. Negative birefringence on polarized microscopy
Tumoral calcinosisPeriarticularAround large joints like the hip, shoulder, and elbowAmorphous multilobulated (cloud-like) appearanceLobules of calcific material surrounded by histiocytic giant cells
Synovial chondromatosisMainly intra-articular, sometimes in bursal tissues and tendon sheathsKnee joint (70%), hip, shoulder, elbowCalcified loose bodies in the joint, ring and arc appearancesCartilage cells with varying degrees of atypia. Varying degrees of calcification and ossification
Myositis ossificansLarge muscle groups of the extremitiesAround the knee, hip, and elbowCircumscribed calcification with a lucent centreInner cellular zone, middle zone of woven bone, outer zone of mineralized bone
BPOPBony surfacesDistal extremities, hands and feetContinuous with the cortex with an underlying intact cortexChondro-osteoid matrix containing enlarged, bizarre, binucleated chondrocytes
LipomaTypically present in the subcutaneous planeUsually found over the back, shoulders, and neck region but can be seen in other locations alsoCalcifications are seen in 11% of the cases.
Larger lipoma can result in bony erosions due to mass effect
Well-circumscribed encapsulated mass of mature adipocytes. Deeper lipomas may be associated with malignant features
Synovial sarcomaSoft tissues of the body. In the extremities seen adjacent to large jointsExtremities, trunk, intrathoracic or intra-abdominalNonspecific calcification patternBiphasic or monophasic forms. Focal calcifications seen in 1/3rd of the cases
ChondrosarcomaLong bonesFemur, pelvisRing and arc (popcorn) types of calcificationsFocal calcifications with no osteoid or bone formation
Parosteal osteosarcomaMetaphysis of long bonesDistal femur, proximal humerus, proximal tibiaLarge lobulated exophytic mass, usually circumferential involvement, central dense ossification; string sign—radiolucent line separating the tumor from the cortexLow grade tumor. Well-formed bony trabeculae and osteoid deposition with or without osteoblastic rimming; stromal cells show mild cellular atypia and few mitoses

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