34 year old construction worker, who sustained an injury ...
“A 34 y/o Male with a Trauma-related Mass in the Right Arm”
California Tumor Tissue Registry’s
Case of the Month
CTTR COTM Vol (8):12
September, 2006
A 34 year-old construction worker fell and acutely bent his right arm backward. The arm enlarged and was painful but lacked numbness, tingling or parenthesis. The patient was seen and admitted from the emergency room for “recent-onset deformity of right arm”. X-rays (Figs. 1, 2) revealed displaced fractures of the mid-portions of the right radius and ulna bones.
During surgery, the orthopedic surgeon was suspicious for pathologic fracture. He scraped tissue from the bone at the regions of fracture and submitted the curettings to pathology characterizing them as being from an arm mass “possibly malignant.”
Microscopically the “mass” consisted of pleomorphic spindled and polygonal stromal cells which formed delicate wisps of osteoid extending into soft tissue including muscle (Fig. 3). There were also regions of cartilaginous differentiation (Fig. 4). Some areas had a fibroblastic stroma producing woven/trabecular bone with calcification (Fig. 5) while others showed osteoclastic “remodeling” (Fig. 6). Only in a few areas were there regions of osteoblastic “rimming” of thickened osteoid trabeculae (Fig. 7). A dominant non-organized cellular proliferation was not seen.
Diagnosis: “Exuberant fracture callus (fibroosseous reparative bone with cartilaginous metaplasia) mimicking osteosarcoma”
Wafaa Elatre, M.D., Fouad Abdelhalim, M.D., Donald R. Chase, M.D,
Department of Pathology, Loma Linda University and Medical Center
California Tumor Tissue Registry
This case illustrates that although reparative bone may show features of malignancy, if guidelines are followed, the correct diagnosis may be rendered. Callus (reparative fibrosseous change) may assume many different histologic appearances dependant upon its age (“chronicity”) or location.
The progressive continuum of reactive features is the most helpful microscopic feature in distinguishing reactive callus from a neoplasm. The presence of a hematoma favors the diagnosis of bone repair. Curiously, if it is surgically removed, healing is retarded. Closely associated with the hematoma are changes of “organization” which include infusion of fibroblasts and myofibroblasts. When osteoid is ultimately laid down, it generally has a rim of benign, plasma-cell-like osteoblasts, however this change is not readily apparent in early callus which has not yet had time to develop, or in late callus which already has formed bone but is undergoing remodeling.
Following a significant fracture, several distinct stages of healing can be identified. The actual break may or may not be identified on the x- ray. The ensuing “induction stage” results in the aforementioned hematoma which incites changes due to release of kinins, prostaglandins and deposition of non-collagenous proteins. Vascular injury at the fracture site may lead to ischemia with osseous necrosis and bone resorption. By approximately the 3rd day, inflammation is evident and characterized by neutrophils with macrophages and mast cells. In this still hypoxic and acidic environment, osteoclasts begin removing necrotic bone. Granulation tissue forms with an infusion of capillaries, fibroblasts and myofibroblasts, and initial collagen deposition. So-called “soft callus” is evident by the first week, demonstrated by an increased vascularity and the proliferation of osteoblasts.
A hard bony structure showing both membranous and endochondral bone formation develops after 3-4 weeks. Following this, a prolonged period of bone remodeling takes place that converts the early stage of woven bone to more mature lamellar bone. This occurs along lines of stress, for example, fracture-related callus in weight-bearing bones may undergo more remodeling than, say cranial-facial bones, and show more osteoclastic cell proliferation.
Features of the fibroosseous reparative condition that may confuse the pathologist are bizarre stromal changes, wispy osteoid production, increased mitotic figures and cartilaginous changes (mimicking a cartilaginous osteosarcoma). The proper interpretation, however, requires correlation with the clinical history (including x-rays), and use of bone repair criteria which include the presence of hematoma, woven bone, osteoblastic rimming and osteoclastic remodeling/resorption.
Suggested Reading:
1. Bolander ME: Regulation of fracture repair by growth factors. Proc Soc Exp Biol Med 200:165-170, 1992.
2. Burchardt AJ, Wagner AA, Basse P: Hyperplastic callus formation in osteogenesis imperfecta: A case report. Acta Radiol 35:426-428,1994.
3. de Palma L, Tulli, Maccauro g, Sabetta SP, del Torto M: Fracture callus in osteopetrosis. Clin Orthop 308:85-89, 1994.
4. Joerring S, Krogsgaard M, Wilbek H, Jensen LT: Collagen turnover after tibial fractures. Arch Orthop Trauma Surg 113:334-336,1994.
5. Massey T, Garst J: Compartment syndrome of the thigh with osteogenesis imperfecta: A case report. Clin Orthop 267:202-205, 1991.
6. Oni OO, Dunning J, Mobbs RJ, Gregg PJ: Clinical factors and the size of the external callus in tibial shaft fractures. Clin Orthop 273:278-283, 1991.
7. Postacchini F, Gumina S, Perugia, De Martino C: Early fracture callus in the diaphysis of human long bone: histologic and ultrastructural study. Clin Orthop 310:218-228, 1995.
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