(1)
Department of Pathology, University of Manitoba Max Rady College of Medicine, Winnipeg, MB, Canada
Keywords
Cartilaginous and osseous tumorsExtraskeletal chondromaExtraskeletal mesenchymal chondrosarcomaExtraskeletal osteosarcomaAlthough usually associated with the bone, tumors with osteoid or chondroid matrix can occur in the soft tissue and are primarily identified by their associated matrix material. Chondroid material has an amorphous eosinophilic to basophilic appearance (Fig. 11.1). The unmineralized part of the bone known as osteoid has an eosinophilic appearance (Fig. 11.2).
Fig. 11.1
Chondroid material with a variably blue and pink appearance. Scattered benign chondrocytes are present (arrow)
Fig. 11.2
Dense eosinophilic osteoid material with areas of early calcification (arrow) in an extraskeletal osteosarcoma
11.1 Extraskeletal Chondroma
Extraskeletal chondroma is a lesion that most often occurs as a slow growing soft tissue nodule in the fingers, toes, and hands and feet of adults in the third and fourth decades of life [1]. On radiologic examination, these neoplasms will display punctate or curvilinear patterns of calcification characteristic of cartilaginous matrix [2].
Pathology
On gross examination, these are well-circumscribed and lobulated lesions that are typically less than 3 cm in size. Microscopically, they are primarily composed of hyalinized cartilage that surrounds bland chondrocytes (Fig. 11.3). Focal areas of myxoid change (Fig. 11.4) and calcification (Fig. 11.5) can be identified [1, 3].
Fig. 11.3
Soft tissue chondroma with mildly increased chondrocytes in the background of a chondroid matrix
Fig. 11.4
Focal myxoid changes (arrow) in the cartilaginous matrix of a soft tissue chondroma
Fig. 11.5
Scattered areas of calcification in the chondroid matrix of a soft tissue chondroma. These correspond to the punctate calcifications seen on radiologic imaging
Ancillary Studies
Although soft tissue chondromas can stain for S-100, the diagnosis is primarily based on the identification of chondroid matrix on an H&E slide.
Differential Diagnosis
Synovial chondromatosis
Enchondroma
Comments
- 1.
Soft tissue chondromas can be confused with other cartilaginous tumors such as synovial chondromatosis or enchondroma.
- 2.
Synovial chondromatosis usually arises within the intra-articular space of large joints such as the knee. Instead of a solitary well-circumscribed nodule, synovial chondromatosis manifests as multiple cartilaginous nodules associated with the synovial membrane.
- 3.
Unlike soft tissue chondroma, enchondroma arises within the bone. Correlation with the radiologic findings helps the pathologist determine whether the lesion arises in the bone or soft tissue.
- 4.
Soft tissue chondromas are benign tumors. Approximately 15% will recur [4].
- 5.
These are generally treated with local excision.
11.2 Extraskeletal Mesenchymal Chondrosarcoma
Extraskeletal mesenchymal chondrosarcoma is a malignancy that most frequently arises in young adults in the second to fourth decades of life [5]. Although this neoplasm most frequently arises in the bone, a minority of cases can present in soft tissue sites such as the head and neck, meninges, and thigh [6].
Pathology
These tumors grossly appear as lobulated and circumscribed masses. Microscopically, they are composed of round cells with scant cytoplasm. A background pattern of branching vessels is present (Fig. 11.6). Focal areas of the tumor show a more mature cartilaginous matrix (Fig. 11.7) [7].
