Chondroblastoma



Chondroblastoma


G. Petur Nielsen, MD

Andrew E. Rosenberg, MD










Specimen radiograph shows chondroblastoma of the femoral condyle. The large tumor fills the medullary cavity, has a lobular configuration, a sharp sclerotic margin, and is lucent with internal mineralization.






Resected femoral condyle contains an intramedullary chondroblastoma. The oval tumor is well circumscribed, tan-pale yellow, and hemorrhagic. The overlying articular cartilage is unremarkable.


TERMINOLOGY


Abbreviations



  • Chondroblastoma (CBA)


Synonyms



  • Calcifying giant cell tumor


  • Codman tumor


  • Epiphyseal chondromatous giant cell tumor


Definitions



  • Benign cartilage-producing neoplasm composed of chondroblasts that typically arises in epiphysis of skeletally immature individuals


ETIOLOGY/PATHOGENESIS


Unknown



  • Presumably develops from mutations in intraosseous mesenchymal stem cells


CLINICAL ISSUES


Epidemiology



  • Incidence



    • Accounts for approximately 1% of primary bone tumors


    • Responsible for < 3% of primary benign bone tumors


    • In individuals younger than 18 years, incidence is 1.18 per million


  • Age



    • Affected individuals are typically skeletally immature, with open growth plates, between ages 10-25 years


    • Rare in young children and elderly


  • Gender



    • More common in males



      • M:F = 2:1


Site



  • Arises in any bone that develops from endochondral ossification


  • Typically develops in epiphysis of long tubular bones (66%)



    • Most common sites are distal and proximal femur, followed by proximal tibia and proximal humerus


    • Approximately 37% limited to epiphysis


    • About 65% involve epiphysis and extend into metaphysis


    • Vast majority are centered in medullary cavity; intracortical and surface tumors are rare


  • Apophyseal origin is less frequent (25%)



    • Usually originates in greater trochanter of femur and greater tuberosity of humerus


  • Bones of hands and feet affected in 10%


  • Other locations include talus, calcaneus, patella, acetabulum, iliac crest, temporal bone, and skull base


  • Tumors arising in metaphyseal and diaphyseal locations are rare


  • Almost all chondroblastomas are solitary



    • Multifocal chondroblastoma is very rare


  • Chondroblastomas in adults develop in unusual locations, such as skull and facial bones


Presentation



  • Pain



    • Tender on palpation


  • Swelling


  • Limitation of range motion


  • Limping


  • Joint stiffness


  • Pathologic fracture through articular surface


Natural History



  • Slow enlargement associated with increase in severity of pain and other symptoms


  • May locally recur following curettage or incomplete resection


  • Metastases develop in < 1% of patients




    • Usually follows multiple recurrences or patients who present with pathologic fracture


  • Malignant transformation very rare


Treatment



  • Curettage and packing with bone graft


  • Percutaneous radiofrequency heat ablation in appropriate cases


  • Resection in selected cases


  • Radiation in tumors that are in critical anatomic locations, such as skull base


Prognosis



  • Local recurrence rate: 14-18%


  • Higher recurrence rate in tumors arising in temporal bone and ribs


  • Local recurrences usually develop within 1st 3 years following curettage



    • May be detected after much longer time interval


  • Pulmonary metastases from histologically benign chondroblastomas are well-recognized phenomenon



    • Metastases are slowly progressive


    • Maintain histologic appearance of benign chondroblastoma


    • Rarely fatal and can be treated with resection


    • Usually develop > 5 years after primary diagnosis


IMAGE FINDINGS


Radiographic Findings



  • Intramedullary, eccentric or central, well-defined tumor with sclerotic margins


  • Predominately radiolucent but frequently contains scattered punctate calcifications


  • May scallop cortex or result in its destruction


  • Neighboring marrow is altered by edema


  • Secondary aneurysmal bone cyst-like changes may cause extensive expansion of bone and periosteal reaction, mimicking a more aggressive neoplasm



    • In chondroblastoma with extensive aneurysmal bone cyst-like changes, it can sometimes be difficult to identify features of underlying primary chondroblastoma


MR Findings



  • Chondroblastoma has low or intermediate signal intensity on T1-weighted image and may be obscured by surrounding edema


  • Tumor has high or variable intensity on T2-weighted image


  • Prominent edema in marrow and soft tissue


  • Joint effusion is common


CT Findings



  • Chondroblastoma is oval, well demarcated, and shows internal calcifications


Bone Scan



  • Marked increased activity on bone scan


MACROSCOPIC FEATURES


General Features



  • Well circumscribed, round or oval, red-gray-white, and gritty


  • Hemorrhagic cystic areas common and are prominent in tumors with secondary aneurysmal bone cyst-like changes


Size



  • Range in size from 1-19 cm (average: 3.6 cm)


  • 85% are ≤ 5 cm


MICROSCOPIC PATHOLOGY


Histologic Features



  • Densely cellular with sharp margins and surrounding reactive bone


  • Composed of admixture of mononuclear chondroblasts and multinucleated osteoclast-type giant cells


  • Chondroblasts grow in sheets, have eosinophilic cytoplasm delineated by well-defined cell borders



  • Nuclei are eccentric, reniform or coffee-bean-shaped, similar to nuclei in Langerhans cell histiocytosis


  • Mitotic activity and regional necrosis may be present, the latter especially in calcified areas


  • Chondroid matrix can be pink or basophilic and sometimes resemble woven bone



    • Well-formed hyaline cartilage uncommon


  • Mineralization of matrix surrounding individual cells imparts characteristic “chicken wire” pattern


  • Osteoclast-type giant cells scattered throughout tumor, usually most numerous in areas of matrix production and hemorrhage



    • Osteoclast-type giant cells are nonneoplastic and recruited by chondroblasts


  • Chondroblastoma abutting temporomandibular joint frequently shows intracytoplasmic hemosiderin deposition mimicking tenosynovial giant cell tumor



    • Some cases reported in literature likely represent tenosynovial giant cell tumor


  • Necrosis in fractured tumors and in areas of prominent calcification


  • Vascular invasion uncommon


  • Concept of “malignant” chondroblastoma is controversial



    • Some pathologists believe that most of these tumors represent either misdiagnosis or radiation-induced sarcoma


  • Term “aggressive chondroblastoma” is used for tumors that histologically have features of chondroblastoma but show destructive growth pattern radiographically


  • Tumor in metastatic deposits similar to that of primary and frequently surrounded by rim of reactive bone


ANCILLARY TESTS


Cytology



  • Clonal abnormalities especially involving chromosomes 5 and 8 have been identified


  • Recent study has shown a balanced t(5;17) in chondroblastoma in chondroblasts but not osteoclasttype giant cells


Immunohistochemistry



  • Chondroblasts express S100 protein and SOX9


  • Tumor cells may stain for muscle actin, keratin, and epithelial membrane antigen


  • Osteoclast-type giant cells stain for histiocytic markers


  • RANKL, a stimulator of osteoclast production and activity, is expressed by tumor cells



    • By this mechanism, osteoclasts are recruited into tumor and produce resorption and lysis of underlying bone


  • Extracellular matrix stains for collagen type II

Jul 6, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Chondroblastoma
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