Bone and Soft-Tissue Disorders
= EXTRASKELETAL CHONDROMA = CHONDROMA OF SOFT PARTS
= rare benign cartilage-forming tumor in extraarticular soft tissue consisting of small nodule of cartilage without connection to underlying bone
Origin: ? embryonal remnants in areas of preexistent fetal cartilage / pluripotential mesenchyme; NOT from mature cartilaginous / osseous tissue
Frequency: 1.5% of all benign soft-tissue tumors
Age: 30–60 (range, 1–85) years; M÷F = 1.2÷1
Histo: lobules of adult-type hyaline cartilage with areas of calcification + ossification; myxoid change; regions of increased cellularity + cytologic atypia
- asymptomatic (usually), slow-growing soft-tissue mass
- occasionally pain + tenderness
Location: hand (54–80%) + foot (20–28%); head & neck (rare): tongue, auricle, cheek, parotid gland, parapharyngeal space, masticator space
- lobulated well-defined extraskeletal mass <2 cm in size
- may contain calcifications (33–70%) with ringlike appearance / ossifications
- scalloping of adjacent bone with sclerotic reaction
CT:
- circumscribed heterogeneously enhancing mass
- TYPICALLY punctate / curvilinear / ringlike chondroid calcifications (in 33–70%)
US:
- well-defined heterogeneously hypoechoic mass
- salient vascularity in subungual area
MR:
- multilobulated mass of high signal intensity on T2WI
- low to intermediate SI relative to muscle on T1WI
- conspicuous peripheral / septal contrast enhancement
Rx: local excision
Prognosis: 15–25% recurrence rate
DDx:
- Extraskeletal myxoid chondrosarcoma (deep-seated in large muscles of upper + lower extremities, pelvic + shoulder girdles)
- Periosteal chondroma
Periosteal (Juxtacortical) Chondroma
= benign hyaline cartilage tumor akin to enchondroma
Origin: deep layer of periosteum
Location: metaphyseal surface of long bones
- radiolucent lesion with variable degrees of chondroid matrix calcifications
- cortical excavation of tissue forming shallow shelving depression = saucerization← local periosteal destruction by tumor + surrounding periosteal reaction
- well-formed periosteal reaction
MR:
- round mass with hyperintense T2 signal ← high water content of chondroid matrix
- adjacent marrow edema (uncommon)
DDx: periosteal chondrosarcoma (size usually >4 cm); periosteal osteosarcoma