Case report 184

Skeletal Radiology Skeletal Radiol (1982) 7:289-292 Case Report 184 Arnold C. Friedman, M.D., Stephen Munderloh, M.D., John E. Madewell, M.D., Alberto Gamez, M.D., MAJ, MC, USA, FACP, and Lennard A. Nadalo, M.D., MAJ MC, USA Department of Radiology, Uniformed Services University of the Health Sciences, Bethesda, Maryland; Department of Radiology, Walter Reed Army Medical Center, Washington, D.C. ; Department of Radiologic Pathology, Armed Forces Institute of Pathology, Washington, D.C., and Department of Pathology, Walter Reed Army Medical Center, Washington, D.C., USA Radiological Study Fig. I. An anteroposterior Fdm of the left femur shows a Iarge soft tissue mass with soft tissue calification extending medially from the femur. Linear periosteal reaction and permeative cortical destruction are present History Address reprint requests to: A,C. Friedman, M.D., Department of Radiologic Pathology, Armed Forces Institute of Pathology, Washington, D.C. 20306, USA A 48-year-old woman presented with a three-month history of a gradually enlarging tender mass in the left thigh with ecchymosis. Five years earlier she underwent an aortic valve replacement for subacute bacterial endocarditis. She had been on Coumadin therapy since replacement of the aortic valve. The mass was initially thought to be soft tissue bleeding secondary to her anticoagulation therapy and was treated with heat and elevation. No history of trauma, puncture wound, diabetes mellitus or drug abuse was obtained. She was admitted to the hospital for evaluation of this gradually enlarging mass. The temperature was 100.2~ F. Physical examination showed a swollen, firm, mildly tender mass in the left thigh, with the circumference measuring 63.5 cm, compared to the normal right side which measured 42.5 cm. A bruit was heard over the left femoral artery. The peripheral pulses were normal with no signs of ischemia in the left leg. Her admission laboratory data revealed a normal WBC of 8,200 with Hct of 31%. Four days after admission the patient developed acute pain in her left thigh with an increase of 2 cm in the circumference of the mass and a drop in the Hct. A plain film of the femur obtained at this time is shown in Figure 1. 0364-2348/82/0007/0289/$01.00 9 1982 International Skeletal Society 290 A.C. Friedman et al. : Case Report 184 Radiological Studies Fig. 2. A transverse sonogram of the proximal portion of the left thigh through the midportion of the mass shows a well defined sonolucent area with good through transmission, compatible with a fluid-containing cavity. Lateral to this sonolucent area is a complex mass representing old blood and necrotic debris Fig. 3. A left femoral arteriogram shows flee extravasation of contrast at the origin of the defined cavity. The deep femoral artery itself is not visualized Pathological Study Fig. 4. A photomicrograph (H and E stain) of the periosteum shows newly formed immature trabecular seams rimmed by large osteoblasts. The interstitial area shows abundant reparative fibroblasts A.C. Friedman et al.: Case Report 184 291 Diagnosis: Mycotic Aneurysm of the Deep Femoral Artery Causing Bone Resorption and Production, Simulating a Primary Bone Neoplasm The differential diagnosis includes a soft tissue sarcoma, myositis ossificans, and primary bone tumor such as osteosarcoma, primary lymphoma of bone, or fibrosarcoma. On the basis of the plain films a primary bone tumor was the initial diagnosis. However, the rapid change in the size of the mass accompanied by the fall of the Hct prompted a sonogram (Fig. 2). The finding of a cystic space in the mass raised the possibility of a mycotic aneurysm and a femoral arteriogram was obtained (Fig. 3) which established the diagnosis. Discussion Surgical exploration demonstrated a large pseudoaneurysm of the deep femoral artery extending from the origin of the deep femoral artery down the thigh along the femur as far as its distal one-third. The pseudoaneurysm was explored and excised. The cavity was approximately 19 cm by 39 cm and contained over 3,000 cc of old and new clotted blood with a well organized fibrous wall. A small amount of bloody pus was identified proximally at the take-off of the deep femoral artery. No distal branches of the profunda could be identified. The soft tissues around the femur contained dystrophic calcification. The periosteum showed perpendicular reparative new bone formation (Fig. 4). Most bony trabeculae ran parallel to each other, with frequent anastomoses. They were lined by large osteoclasts and the intermingling connective tissue was composed of young reparative fibroblasts. The femur was exposed through the periosteum and was found to contain numerous holes, corresponding to the radiological permeative pattern. This probably occurred from osteoclastic activity stimulated by active hyperemia due to the soft tissue inflammatory process. Culture of the tissue from the pseudoaneurysm grew alphahemolytic streptococcus, the same organism cultured from the aortic valve five years earlier. Cultures of the periosteum and bone were negative. Mycotic aneurysms are uncommon but are not rare lesions. Their incidence has decreased in the post antibiotic era. Koch has been credited with the original pathological description of mycotic aneurysm. However, Virchow in 1847 was one of the ftrst to recognize embolism in cases of infectious endocarditis and destruction of the vascular wall at the embolic sites. Osler originated the term of mycotic aneurysm when he described an aortic aneurysm arising from bacterial endocarditis in 1885. These aneurysms can occur in all age groups with involvement of many systemic vessels. Clinical symptoms and physical findings are associated with the particular artery involved and have a wide spectrum of presentations. The clinical symptoms and destruc- tion of the arterial wall usually progress rapidly and thus early recognition and angiographic evaluation are critical. In this case the clinical symptoms were insidious and of prolonged nature (at least 3 months) which is somewhat atypical. Arteries which are frequently involved are in thoracic aorta (ascending aorta and arch), superior mesenteric artery, intracraniaI vessels and large arteries of the extremities (femoral and brachial arteries). Occasionally, multiple arteries may be involved by the process. When the aneurysms are located in the peripheral arteries a more favorable outcome may result since these are usually superficial and accessible to earlier diagnosis. Spontaneous regression and cures due to thrombosis have been reported. Mycotic aneurysms usually require a source of infection and damage to the vascular wall for their development. The infectious source is most commonly bacterial endocarditis; however, many other sources of infection may be responsible. The process damaging the wall is usually atherosclerosis, but cystic medial necrosis, syphilitic aortitis, external trauma and coarctation or hypoplasia of a vessel are other causes. The compromised vascular endothelium is important in the pathogenesis because the healthy intima is resistant to infection. The most common sites of implantation are the abnormal intima or the vasa vasorum; however, an infected embolus may be located in a normal vessel at a bifurcation, sharp narrowing or sharp turn. Occasionally, mycotic aneuryms can develop from contiguous extension of infection from an extravascular source. Once the infection is established, the arterial wall can rapidly disintegrate and rupture at any time or the destruction may proceed slowly with true aneurysm formation. Another possibility is perforation of the artery and pseudoaneurysm formation as in the current case. This usually occurs in peripheral arterial sites. The bony changes noted in this case are of interest since they prompted a consideration of primary bone tumor. Three features are illustrated: (1) periosteal reaction; (2) soft tissue calcification; and (3) cortical 292 destruction. These Findings under most circumstances would mandate a diagnosis of a primary skeletal or even a soft tissue neoplasm. References 1. Bennett DE, Cherry JK (1967) Bacterial infection of aortic aneurysms: A clinicopathologic study. Am J Surg 113:321 326 2. Kaufman SL, White RI, Harrington DP, Barth KH, Siegelman SS (1978) Protean manifestations of mycotic aneurysms. AIR 131 : 1019-1025 3. Lewis D, Schrager DL (1909) Embolomycotic aneurysms. JAMA 53:1808-1814 4. Nabseth DC, Deterling RA Jr (1961) Surgical mamagement of mycotic aneurysm. Surgery 50:347-353 5. Olmstead WW, McGee TP (t977) The pathogenesis of peripher- A.C. Friedman et al. : Case Report 184 al aneurysms of the central nervous system. A subject review from the AFIP. Radiology 123:661~66 6. Osier W (1885) The Gultonian lectures on malignant endocardifis. Br J Med 1:467-470 7. Parkhurst GF, Decker JP (1955) Bacterial aortitis and mycotic aneurysm of the aorta. A report of twelve cases. Am J Pathol 31:831-835 8. Revell STR (1945) Primary mycotic aneurysms. Ann Intern Med 22:431-440 9. Robbins SL (1974) Pathologic basis of disease. WB Saunders, Philadelphia London Toronto 10. Skandalakis JE, Edwards BF, Gray SW, Davis BN, Hopkins WA (1960) Coarctation of aorta with aneurysm. Internat Abstr Surg 111:307-326 11. Suwanwela C, Suwanwela N, Choruchinola S (1972) Intracranial mycotic aneurysms of extravascu]ar origin. J Neurosurg 36: 552-559 12. Weintxaub RA, Abrams HL (1968) Mycotic aneurysms. AJR 102:354-362