Misdiagnosis of a chylous cyst as chest wall gouty tophusA case of true pseudogout.код для вставкиСкачать
ARTHRITIS & RHEUMATISM Vol. 56, No. 11, November 2007, pp 3854–3857 DOI 10.1002/art.22957 © 2007, American College of Rheumatology Misdiagnosis of a Chylous Cyst as Chest Wall Gouty Tophus A Case of True Pseudogout Leena G. Adhikesavan,1 William T. Ayoub,2 and H. Ralph Schumacher3 to the left sternoclavicular joint and extending anterior to that joint, in the region of the sternal head of the left sternocleidomastoid muscle. There was no bony erosion. The patient’s primary physician referred him to a pathologist, who performed a fine-needle aspiration. The pathologist found birefringent crystals that were interpreted to be monosodium urate. Another 6 months passed before the patient was referred to a thoracic surgeon. A physical examination at that time revealed a 4–5-cm soft, slightly tender mass located in the sternoclavicular area, slightly toward the left of midline, although extending across the midline. His serum uric acid level was 4.9 mg/dl. Excision of the mass was performed. At the time of surgery, the surgeon thought that the mass was arising from the sternoclavicular joint. The cystic mass was found to consist of a yellowish pasty material, and the pathologic diagnosis of the cyst was histiocytic reaction to foreign material consistent with gout. There were no inflammatory or malignant cells. There was no further evaluation or treatment at that time. The mass reappeared in a few months. Approximately 6 months after excision, the patient was referred to the rheumatology department for treatment of presumed tophaceous gout. He was an otherwise healthy man who had never had a gout attack. He denied having any pain. Physical examination revealed 2 masses: one was larger than a golf ball and was centrally located in the superior aspect of the sternum; the other was marble sized and was located just inferior to, and to the left of, the larger mass (Figure 1). No tophi were noted anywhere else. Fine-needle aspiration yielded a thick, yellowgreen material in the hub of the needle, but then ⬃15 ml of off-white liquid (Figure 2) was aspirated from the center of the larger mass. Microscopic examination of a dried slide of the aspirate revealed birefringent material, but no distinct needle-shaped crystals (Figure 3). Part of A patient referred to us for recurrent chest wall gouty tophus, but who was determined to actually have a chylous cyst, is described herein. Chylous cysts of the neck or chest wall can be caused by thoracic duct injury. Chyle contains 4–40 gm/liter of lipids, mostly triglycerides, and these can form birefringent crystals upon drying, leading to a false diagnosis of gout. The diagnosis of neck masses can be confirmed in most cases based on the patient’s medical history and a physical examination, along with imaging studies and fine needle aspiration. We describe a patient who was referred to us for recurrent chest wall gouty tophus but who was actually determined to have a chylous cyst. CASE REPORT The patient, a 48-year-old man, was referred to us to consider treatment for tophaceous gout. He developed a chest wall mass 2 years prior to presentation. The mass appeared a few days after he noticed some pain in his chest while squeezing the handles on a pruning tool. He did not seek medical attention for several months. A chest radiograph and radiographs of the sternoclavicular joints revealed no abnormalities. Computed axial tomography (CAT) showed a 5-cm soft tissue density superior 1 Leena G. Adhikesavan, MD: Geisinger Medical Center, Danville, Pennsylvania; 2William T. Ayoub, MD: Geisinger Medical Group at State College, State College, Pennsylvania; 3H. Ralph Schumacher, MD: University of Pennsylvania VA Medical Center, Philadelphia, Pennsylvania. Address correspondence and reprint requests to William T. Ayoub, MD, Associate, Geisinger Medical Group at State College, Department of Rheumatology, 200 Scenery Drive, State College, PA 16801 (e-mail: firstname.lastname@example.org); or to Leena G. Adhikesavan, MD, Rheumatology Fellow, Geisinger Medical Center, 100 North Academy Avenue, Danville, PA 17822 (e-mail: lgadhikesavan@ geisinger.edu). Submitted for publication June 4, 2007; accepted in revised form July 12, 2007. 3854 MISDIAGNOSIS OF A CHYLOUS CYST 3855 Figure 3. Polymorphous, birefringent crystals from the aspirated material (original magnification ⫻ 300). Figure 1. The patient’s chest mass. the specimen was sent to a rheumatologist (HRS) for further investigation. Analysis revealed droplets typical of neutral lipids (Figure 4), but no needle-shaped crystals. The gross and microscopic appearance was thought to be characteristic of chyle, and an investigation for lymphatic obstruction was suggested. The patient was referred back to the thoracic surgeon for treatment of the chylous cyst. Magnetic resonance imaging (MRI) revealed a 7-cm ⫻ 5-cm cystic mass in the sternal notch area of the lower anterior neck that was partially displacing the medial margins of the strap muscles. The patient was diagnosed as having a chylous cyst secondary to traumatic disruption of the thoracic duct, possibly initially from the strain of using the pruning tool and then from the surgery. He under- Figure 2. Fluid aspirated from the chest mass. went surgical exploration and division of the thoracic duct by ligation. Multiple areas of chyle leak were identified, and major branches of the duct were ligated and clipped. The main duct was found to be avulsed and was also ligated. The patient is doing well now, with no recurrence of the neck swelling. DISCUSSION Chylous cysts are rare. Chyle is lymphatic fluid of intestinal origin, which is carried by the thoracic duct to the bloodstream. Due to the fact that chyle is found only in the mesentery of the small intestine and the thoracic duct, chylous cysts are usually seen within the mesentery of the small intestine or in the retroperitoneum (1,2). Very few chylous cysts of the neck have been reported (2–5). Information on the natural history and pathogenesis of these cysts is limited (4). Weakness in the thoracic duct wall could be congenital or degenera- Figure 4. Droplets of neutral lipid characteristic of chyle (original magnification ⫻ 300). 3856 tive (6,7). Thoracic duct injury is a rare but known complication of thoracic surgeries, esophagectomy (8), jugular vein or subclavian vein catheterization (9,10), or penetrating or blunt trauma (11,12). This patient probably injured his thoracic duct while squeezing the handles on the pruning tool. Radiography, ultrasonography, CAT, and MRI are useful imaging techniques in determining the consistency and the anatomic boundaries of chylous cysts. Simple aspiration is an unsuccessful therapy due to rapid reaccumulation, since these cysts are connected to adjacent lymphatic structures (2–4). The incidence of malignancy has been reported to be 22% in one study (1) and 33% in another (13), so complete excision is recommended. Gout is best diagnosed when negatively birefringent, needle-shaped monosodium urate crystals are viewed using polarized light microscopy. Gout may involve the chest wall by affecting sternoclavicular (14,15), costochondral (14), or manubriosternal (16,17) articulations. Subcutaneous tophus formation by crystal deposition is rare in other conditions except gout. There are a few cases where it has been reported in association with hydroxyapatite (18), calcium pyrophosphate dihydrate (19,20), and calcium oxalate (21) crystals. Subcutaneous cholesterol “tophi” have been reported in 2 cases, both of which were initially mistaken for a gouty tophus (22). Cholesterol crystals are found occasionally in synovial effusions from patients with rheumatoid arthritis (23), ankylosing spondylitis (23), bursitis (23, 24), and osteoarthritis (25). Although most cholesterol crystals are flat, rectangular, and rhomboid, and resemble broad plates with a notched corner, needle forms can also be seen (25–27), which can lead to the false diagnosis of gout. Neutral lipids can also form birefringent crystals upon drying (28), which probably explains the initial confusion about the appearance of the aspirate on the dried slide. In this case, the location and relatively rapid appearance of the mass are not typical of a gouty tophus. No other findings suggestive of gouty arthritis were obtained from the patient’s medical history or physical examination. The appearance of monosodium urate crystals when examined by polarizing light microscopy is quite distinct and diagnostic. In order to accurately diagnose gout, crystalline material should contain distinct needle-shaped crystals that are strongly negatively birefringent. In this case, the microscopic appearance was that of a birefringent irregular material without diagnostic needle-shaped crystals. Although chylous ADHIKESAVAN ET AL cysts are rare, they must be considered as one of the differential diagnoses of chest masses. AUTHOR CONTRIBUTIONS Dr. Adhikesavan had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Study design. Adhikesavan. Acquisition of data. Adhikesavan, Ayoub, Schumacher. Analysis and interpretation of data. Adhikesavan, Ayoub, Schumacher. Manuscript preparation. Adhikesavan, Ayoub. REFERENCES 1. Engel S, Clagett TO, Harrison EG. Chylous cysts of the abdomen. Surgery 1961;50:593–9. 2. Kohnoe S, Emi Y, Yamamura S, Hattori T, Sugimachi K. Chylous cyst of the neck in an adult. 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