24 yo man with right-sided lower posterior chest/rib pain for 4-6 months, increases with deep inspiration. He denies history of trauma.
Tenderness to palpation approximately at posterior rib 11
â€¢ right paraspinal chest wall mass
â€¢ measures 6.9x4.7x4.6 cm
â€¢ located at levels T8 - T10
â€¢ mass erodes into T9 & T10 vertebral bodies, T9 pedicle, rib 9
â€¢ does not appear to disrupt thecal sac, though neural foramina is eroded
â€¢ mild enhancement with gadolinium on T1 MR
â€¢ sclerotic margins present in surrounding eroded structures
â€¢ multiple fluid-fluid levels on T2
â€¢ no pathologic lymphadenopathy
â€¢ no other abnormal findings are noted
Â» Benign Primary Bone Tumors
â€¢ fibrous dysplasia
â€¢ chondromyxoid fibroma
â€¢ giant cell tumor
Â» Malignant Primary Bone Tumors
â€¢ osteoblastoma, aggressive variant
â€¢ aneurysmal bone cyst
â€¢ neurogenic tumors
Dx: Chondroblastoma with secondary aneurysmal bone cyst
Dx Confirmed by: Core biopsy and pathology
After CT-guided core biopsies were obtained, the patient was scheduled for metastatic work-up with whole body bone scan, PET, and brain MR. As of submission date, the patient continues to be in the diagnostic stages of medical care and planning.
Surgery is likely to be planned, as most of these primary bone tumors must be removed by en bloc resection. Despite their benign taxonomy, a majority of these benign lesions tend to recur, therefore making wide excision standard regardless of malignant potential.
Paraspinal masses can invoke an enormous list of differential diagnoses: lymphoma, metastatic disease, nerve sheath tumors, primary bone tumors, myeloma, meningocele, cysts, abscesses, and beyond. Based on location and radiographic appearance, this particular patient's findings suggested a neoplastic process, which directed him to biopsy. Indeed biopsy results initially indicated that a primary bone neoplasm was probable, based on presence of osteoblasts and cartilage.
Primary bone tumors are relatively rare, with an incidence of approximately 10,000 cases a year in the US. Using the patient's demographics as well as radiographic features can narrow the differential significantly. The suspected neoplasms, with the exception of chondrosarcoma, fit this patientâ€™s age group, as all frequently present in the second and third decades (chondrosarcoma has a peak incidence in the 5th and 6th decades of life). Using mass location to assign a probably diagnosis, an osteoblastoma becomes likely as it is often found in the spinal elements. By histology, of the differentials listed, the primary bone neoplasms seem most probable as those tumors are associated with chondro-osseous derivatives. More distinctively, the radiographic features suggest that there is a cystic component to the tumor, likely aneurysmal bone cysts. Because only a small fraction of the tumor contains these structures, they are likely to be secondary versus a primary aneurysmal bone cyst.
When considering primary bone tumors with secondary aneurysmal bone cyst components, the differential is further pointed. Only 5 types of primary bone tumors typically display this pattern: giant cell tumor of bone, osteoblastoma, chondroblastoma, fibrous dysplasia, and telangiectatic osteosarcoma.
Final pathology reading of the core biopsy revealed the tumor was a chondroblastoma. This is a very rare tumor, and even rarer is the location of the tumor in this patient. Chondroblastomas account for less than 1% of all bone tumors; this corresponds to approximately 100 cases a year, considering the scarcity of primary bone tumors in general. Additionally, nearly 75% of the cases occur in the long bones of the lower extremity - distal femur and proximal tibia/fibula. Another 20% of chondroblastomas occur in the humerus, while a small fraction has also been reported in the small bones of the hand and feet. Case reports have described these tumors occurring in the skull, mandible, maxilla, vertebra, ribs, scapula, patella, and sternum.
This patient fits the expected demographics of the majority of primary bone tumors: second decade in age, male, black, history of chronic pain. What is so profound regarding this case remains the specific type of primary bone tumor, given its rarity by statistical incidence, and its unusual location originating from the ninth rib.
Bullough, Peter. Orthopaedic Pathologv (third edition). Times Mirror International Publishers Limited: London, 1997.
Fines, Bonnie and Stacey, Gregory. Chondroblastoma, Radiology, Musculoskeletal. EMedicine Online. Last updated July 19, 2006. Accessed on March 2, 2007.
Gitelis, S. et al. Benign Bone Tumors. Instructional Course Lectures, 45:p. 426-46, 1991. Accessed via EMedicine on 2/26/07.
Morgan, Hannah and Damron, Timothy. Chondroblastoma, Surgery, Orthopedic. EMedicine Online. Last updated March 15, 2005. Accessed information March 2, 2007.
Murphey, Mark D. Fundamental Concepts of Musculoskeletal Neoplasm: Radiographs. Lecture given at USUHS. 2/28/07.
Primary Bone Tumors. Journal of Cancer Control. Vol. 13, No. 4. Moffitt Cancer Center. Accessed via Medscape on 2/25/2007.
The following list describes some familiar features tumors of the chondro-osseous origin, with mean age of presentation, most common anatomic location, likely radiographic findings, and histologic correlation given for each tumor.
â€¢ long bones, femur
â€¢ lobulated mass, scalloped cortical margins, calcifications, cysts
â€¢ chondroid matrix
â€¢ 20's & 30's
â€¢ metaphysis of tibula/fibula
â€¢ eccentric lytic lesion, decreased signal on T1
â€¢ chondroid matrix with cytologic features of anaplastic processes
â€¢ teens & 20's
â€¢ long bones, around knee
â€¢ can be exophytic, but generally subperiosteal
â€¢ osteoid and cartilage
â€¢ long bones
â€¢ solitary, locally aggressive, highly expansile
â€¢ giant cells
â€¢ long bones
â€¢ oval, lytic, scalloped cortex
â€¢ cartilage with layer of smooth, thin bone surrounding
â€¢ 50's & 60's
â€¢ femur, humerus, ribs, pelvis
â€¢ luceny, calcifications, scalloped edges, and extension into soft tissues
â€¢ cartilage with anaplasia
osteoblastoma, aggressive variant
â€¢ spine - vertebra and posterior elements
â€¢ varies - lucent to sclerotic, can be expansile, adjacent bone thinning
â€¢ osteoid, osteoblasts, spindle cells, cartilage (rare)
â€¢ teens - 30's
â€¢ long bones (knee)
â€¢ vary - lytic, sclerotic, mixed
â€¢ osteoblasts, chondroblasts, fibroblasts
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