College of American Pathologists

2011 — September Case of the Month

Posted September 6, 2011


CAP Foundation September 2011 Online Case of the Month

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After reading the summary, try answering the three related multiple-choice questions below.

A 49-year-old woman, with a radiologically aggressive pelvic mass underwent a left hemipelvectomy. A 15.0 x 11.0 x 9.0 cm tan-yellow mass occupying the medullary cavity of the iliac bone and extending into the surrounding soft tissues was identified. The cut surface of the mass was variegated tan-brown and myxoid with large foci of necrosis intermixed with areas having a more blue-gray chondroid appearance.

Archive Case and Diagnosis: This case first appeared as Performance Improvement Program in Surgical Pathology (PIP) 2008, Case 30, and is chondrosarcoma.

Criteria for Diagnosis and Comments: The diagnosis is chondrosarcoma (CS). By definition CS is a malignant tumor of bone with hyaline cartilage differentiation. Although reactive endochondral bone can be present in these tumors as a minor component in the absence of dedifferentiation, osteoid is not produced by the neoplastic cells. CS is the third most common malignant bone tumor after myeloma and osteosarcoma and usually occurs in the fifth to seventh decades of life. The tumor most typically involves the metaphysis of the long bones with the proximal and distal femur, proximal humerus and tibia being the most common locations, followed by the pelvic bones.

Clinically, CS presents as a relatively slow growing mass or as pain. Radiographic studies are critical in differentiating chondrosarcoma from benign cartilaginous tumors like enchondroma or osteochondroma. The tumor usually presents as an intramedullary radiolucent lesion, centered in the metaphysis of the bone, with variably distributed punctate or ring-like opacities. The cortex of the bone is often thickened with inner scalloping or frank destruction. An absent or scant periosteal reaction is the norm.

Chondrosarcomas can be classified as primary, or arising “de novo”, and secondary, or arising in a preexisting benign cartilaginous lesion such as enchondroma or osteochondroma. Histologically, chondrosarcomas may be classified as conventional, clear cell, myxoid, mesenchymal, or dedifferentiated. The conventional type shows lobules of hyaline cartilage with increased cellularity and enlarged chondrocytes with more or less conspicuous nuclear chromatin detail. The cartilage infiltrates the native bony trabeculae, having a permeative growth pattern, and is frequently found within the Haversian canals.

Chondrosarcomas are graded as low, intermediate, and high grade proportional to the degree of cellularity, presence of conspicuous nuclear detail, and mitotic activity. The permeation of the native bone is the most important histologic criterion in differentiating a low grade chondrosarcoma from a benign cartilaginous lesion. Myxoid degeneration and necrosis of the cartilage are strongly suggestive of an intermediary grade of malignancy. Mitotic figures including atypical forms highlight high-grade lesions. However, in the absence of a radiologically destructive lesion, one must be extremely careful when diagnosing a chondrosarcoma, especially in small biopsies. Also, one must keep in mind that in the setting of Ollier disease, hereditary multiple osteochondromas or enchondromas of the small bones of the hands and feet, a moderate degree of chondrocyte pleomorphism and increased cellularity is accepted as being within the realm of benignity. The cytogenetics and molecular genetics of CS and other cartilaginous lesions have begun to be unraveled and may eventually assist in reaching a diagnosis.

Osteosarcomas are malignant tumors of mesodermal origin in which the tumor cells produce bone (also referred to as “tumor bone”) or osteoid albeit occasionally in very small amounts. The neoplastic cells can also produce chondroid matrix, which when predominant can lead to a misdiagnosis of chondrosarcoma, however, several major differences can help in differentiating chondroblastic osteosarcoma from chondrosarcoma. These include the clinical demographics including the age of the patient, the radiographic appearance, and the histopathology.

Osteosarcoma is a malignancy predominantly of teenagers and young adults with a peak frequency in the second to third decades of life. It usually involves the metaphyseal region of long bones and radiographically present as a radiolucent lesion with ill defined margins and mottled areas of radiodensity, frequently associated with a soft tissue mass and marked periosteal reaction. A second peak of occurrence later in life is often associated with underlying diseases of bone including Paget disease, fibrous dysplasia or long-term prior injury such as that associated with irradiation.

Dedifferentiated chondrosarcoma is characterized by the presence of two components, a well differentiated (low grade) chondrosarcoma juxtaposed to a high grade non cartilaginous sarcoma, with abrupt transition between the two. The high grade sarcomatous component can be histologically variable ranging from pleomorphic sarcoma to fibrosarcoma and osteosarcoma.

Enchondroma is a common benign hyaline cartilage neoplasm involving the medullary cavity of bones. It can be solitary or multiple, as part of familial enchondromatoses, Ollier disease or Maffucci syndrome. Enchondromas frequently arise in the small bones of the hands and feet where they expand the bone, attenuate the cortex and often present as pathologic fractures. When arising in the long bones, enchondromas are usually located in the metaphysis and do not significantly expand the bone or scallop the cortex. Radiographically, enchondromas are radiolucent lesions with varied degrees of mineralization which typically have punctate, flocculent ring or arc-like patterns. In the absence of pathologic fracture, pain is not a feature of this neoplasm and, when present, a more aggressive tumor should be taken into consideration.

Synovial chondromatosis is an uncommon benign nodular cartilaginous proliferation arising in the synovium of joints, bursae, or tendon sheaths. It has a predilection for adult males and the knee joint. Patients present with nonspecific symptoms including recurrent pain, joint stiffness, locking, and swelling. A soft tissue mass adjacent to the joint is sometimes present. Histologically, the cartilage nodules are surrounded by a thin fibrous or synovial membranes and show variable cellularity with clonal arrangements of chondrocytes. A moderate degree of cellular pleomorphism as well as rare binucleated chondrocytes are acceptable. Bone, resulting from the process of endochondral ossification is sometimes seen at the periphery of the cartilage nodules.

Supplementary Questions:

Question Diagnostic Set
1. Which primary bone tumor is characterized by production of both high grade neoplastic cartilage and osteoid? A. Chondroblastic osteosarcoma
B. Chondrosarcoma
C. Dedifferentiated chondrosarcoma
D. Enchondroma
E. Synovial chondromatosis
2. Which neoplasm is characterized by production of extraosseous lobules of bland hyaline cartilage with mildly increased cellularity, “clonal” arrangement of chondrocytes and nesting within a thin connective tissue membrane? A. Chondroblastic osteosarcoma
B. Chondrosarcoma
C. Dedifferentiated chondrosarcoma
D. Enchondroma
E. Synovial chondromatosis
3. Which bone neoplasm is characterized by juxtaposition of low grade neoplastic hyaline cartilage and high grade pleomorphic sarcoma? A. Chondroblastic osteosarcoma
B. Chondrosarcoma
C. Dedifferentiated chondrosarcoma
D. Enchondroma
E. Synovial chondromatosis


  1. Bell WC, Klein MJ, Pitt MJ, Siegal GP Molecular pathology of chondroid neoplasms: Part I - benign lesions and Part II - malignant neoplasms. Skeletal Radiol. 2006; 35:805-813,887-894.
  2. Campanacci M. Bone and Soft Tissue Tumors. In: Clinical Features, Imaging, Pathology and Treatment. New York; Springer-Verlag; 1999.
  3. Fletcher C D M, Unni KK, et al. Pathology and genetics of tumors of soft tissue and bone. Lyon, France: IARC Press; 2002.
  4. Klein M J, Siegal GP. Osteosarcoma: anatomic and histologic variants. Am J Clin Pathol. 2006; 125(4):555-581.
  5. McCarthy E F, Frassica FJ. Pathology of Bone and Joint Disorders with Clinical and Radiographic Correlation. Philadelphia, PA: Saunders; 1998.
  6. Rozeman LB, Cleton-Jansen AM, Hogendoorn PCW.  Pathology of primary malignant bone and cartilage tumors. Int Orthop. 2006; 30:437-444

Luminita Rezeanu, MD
University of Alabama at Birmingham
Birmingham, AL

Gene P. Siegal, MD, PhD, FCAP
Surgical Pathology Committee
University of Alabama at Birmingham
Birmingham, AL