[52] Chondroblastoma-Like Osteosarcoma: A Clinicopathologic Review of 17 Cases

A Bahrami, K Unni, F Bertoni, P Bacchini, H Dorfman, T Nojima, C Inwards. Mayo Clinic, Rochester; Casa di Cura Villa Erbosa, Bologna, Italy; Montefiore Medical Center, New York; Kanazawa Medical University, Uchinada, Japan

Background: Chondroblastoma-like osteosarcoma (CBL-like OS) is an exceedingly rare histologic variant of OS that morphologically simulates CBL. Although this subtype is recognized in the WHO classification of bone tumors and bone pathology textbooks, there are only two documented cases in the literature.
Design: We conducted a clinicopathologic and radiographic review of 17 cases collected from 3 large consultative practices of OS showing histologic features resembling CBL. Histologic sections from the primary tumor (all cases) and pulmonary metastases (2 cases) were reviewed. Radiographic information was available on 13 cases.
Results: The tumors occurred in 9 M and 8 F with a median age of 35 years (range, 13-72 years), and involved the following bones: metatarsus (3 cases); femur (3 cases); rib (3 cases); humerus (2 cases); and talus, phalanx, tibia, fibula, ischium and ilium (1 each). In the long bones, tumors arose in the meta-diaphysis (6 cases) and epiphysis (1 case). The constant histologic feature that simulated CBL was the diffuse growth of monotonous, minimally to moderately atypical rounded cells with ovoid nuclei. Cytologic atypia was more pronounced in recurrent tumors. The most helpful feature of malignancy was destructive permeation of host bone/soft tissue. The tumors also showed a variable pattern of abnormal bone production including diffuse sheets of dense osteoid, heavy irregular trabeculae of bone, and coarse or linear calcification of woven bone. The pulmonary metastases had histologic features of OS. 13 tumors had malignant or worrisome radiographic findings, and 1case was equivocal. Of patients with follow-up information, 6 developed one or more local recurrences, 2 developed pulmonary metastases, and 2 died of disease.
Conclusions: We confirmed a subtype of OS resembling CBL. In a tumor with cytologic features similar to CBL, histologic evidence of destructive growth and/or abnormal pattern of bone production should raise the possibility of CBL-like OS, particularly if the tumor is located in an unusual site for CBL or has radiographic findings suggesting malignancy.
Category: Bone & Soft Tissue

Tuesday, March 23, 2010 9:30 AM

Poster Session III # 11, Tuesday Morning


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