Radiological Reasoning: Acutely Painful Swollen Finger. Musculoskeletal Imaging Chew and Richardson Benign-Appearing Bone Mass.

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1 Musculoskeletal Imaging Chew and Richardson Benign-Appearing Bone Mass AJR Integrative Imaging LIFELONG LEARNING FOR RADIOLOGY This Radiological Reasoning article is available for SAM credit and CME credits when completed with the additional educational material provided in Imaging Evaluation of Tendon Sheath Disease: Self-Assessment Module. See page S10 for details. AJR 2007;188:S13 S X/07/1883 S13 American Roentgen Ray Society Patrick T. Liu 1 Liu AJR Integrative Imaging Liu PT Radiological Reasoning: Objective The purpose of this article is to review the differential diagnosis of finger masses and their imaging appearances. Conclusion Giant cell tumor of the tendon sheath is a slowly growing, benign tumor of the synovium that commonly presents as a painless nodular mass in the hand or wrist. Also termed localized nodular tenosynovitis, these tumors are the most common soft-tissue tumors of the hand. Occasionally, these tumors can present with pain when traumatized, and they should be suspected when a firm, rubbery mass is found at the location of a tendon sheath. Case History A 22-year-old man presents to the emergency department with acute onset of pain and swelling in the volar portion of the middle finger on his left hand. The pain arose while he was carrying a load of groceries in plastic bags, and his entire finger began to swell at that time. Physical examination reveals fusiform diffuse enlargement and erythema of the middle finger. This digit is extremely tender to palpation from the distal interphalangeal joint to the distal palmar crease. The patient is unable to fully extend the finger. The skin of the middle finger and hand is intact, and the patient has experienced no fever or chills. He has no relevant medical history. However, on further questioning, the patient admits that this finger has been swollen intermittently for the past 2 years, but it has never been painful. Radiography (not shown) shows diffuse soft-tissue swelling of the volar aspect of the middle finger but no underlying bone abnormality. MRI of the middle finger is performed (Figs. 1A 1E) approximately 8 hours after presentation. MRI MRI of the hand reveals an elongated soft-tissue mass in the volar soft tissue of the middle finger extending from the level of the metacarpophalangeal joint to the mid portion of the distal phalanx. The nodular mass is seen abutting the flexor digitorum tendons without invasion, and it appears to lie within the tendon sheath. Although the proximal half of the mass has areas of moderate to high T2 signal, the distal half of the mass is composed of nodular areas of hypointense T1 and T2 signal. After the IV injection of gadolinium, the nodular tissue enhances diffusely to a moderate degree. No underlying bone or joint abnormality is seen. S13

2 Liu Expert Discussion (Dr. Liu) On clinical grounds, the differential diagnosis revolves around acute, painful lesions of the finger with swelling, and includes tear of the flexor digitorum profundus tendon, subcutaneous hematoma, and infectious tenosynovitis. On imaging grounds, the differential diagnosis revolves around masses involving tendons, and includes giant cell tumor of the tendon sheath, fibroma of the tendon sheath, palmar fibromatosis, synovial chondromatosis, and hemangioma. We will consider each of these in turn. The flexor digitorum profundus tendon lies directly deep in relation to the elongated soft-tissue mass. Although the tendon at the level of the middle phalanx has a region of intermediate signal on the sagittal T1-weighted sequence (Fig. 1A), the tendon has normal low signal on the T2-weighted sequence (Fig. 1B) and has a normal configuration, inserting on the base of the distal phalanx. It is this lack of T2-weighted abnormality that makes a tendon injury unlikely. The intermediate signal on the T1-weighted image is likely due to the magic angle phenomenon, which refers to increased signal in normal tendons and ligaments that occurs on sequences with short TE values (< 37 msec) when their fibers are oriented at 55 ± 10 relative to the B 0 magnetic field [1]. With the history of an acute onset of symptoms, a hematoma would be expected to show a unilocular configuration with more mass effect. One would also anticipate the presence of signal characteristics of acute or subacute hemorrhage, with areas of fluid that appear hyperintense to skeletal muscle on both the T1- and T2-weighted sequences. Internal enhancement in acute hematomas would be rare once the bleeding ceases. Fluid fluid levels may be seen if the collection contains various stages of blood breakdown products. The lack of increased fluid in the tendon sheath indicates that no acute tenosynovitis is present. Chronic infectious tenosynovitis may result in thickening of inflamed synovium, but not to the degree seen in this patient [2, 3]. Inflamed synovium usually has homogeneous intermediate signal on T2-weighted images and enhances markedly after gadolinium injection. The large areas of low signal found in the mass on the T1- and T2-weighted images indicate fibrous composition, calcification, or hemosiderin deposition. However, calcification is not visible on the radiographs. This MRI appearance, combined with the multinodular configuration, the painless slow growth, and the location adjacent to a tendon, are all characteristic findings of giant cell tumor of the tendon sheath. On T1- weighted MRI sequences, the lesions of giant cell tumor of the tendon sheath characteristically have signal intensity similar to or slightly hyperintense to skeletal muscle. On T2-weighted sequences, the masses are also iso- to hypointense to skeletal muscle and interspersed with scattered areas of lower and higher signal. Gadolinium injection has been reported to result in moderate to intense enhancement [4, 5]. The areas of moderate to high T2 signal in this patient s mass are probably edema or hemorrhage caused by the recent grocery bag related trauma. Giant cell tumor of the tendon sheath would be the preferred diagnosis. Palmar fibromatosis, or Dupuytren s contracture of the hand, is characterized by collagen deposits in the subcutaneous tissue of the palm and fingers, with thin chord-shaped configuration in the fingers and nodular configuration at the distal palmar crease. The lesions in palmar fibromatosis are more elongated and much less bulky than the mass seen in this case. On MRI, the collagen deposits have low, very hypointense signal on both T1- and T2-weighted sequences in the fingers but may have some intermediate signal on T2-weighted images if they occur in the palm [6]. Synovial chondromatosis can occur in tendon sheaths, but one should be able to find large amounts of tendon sheath fluid and multiple small, loose ovoid bodies. The bodies may have MRI signal characteristics of fibrocartilage, calcification, or bone marrow, depending on the degree of ossification [7]. Fibromas of the tendon sheath also occur commonly in the hand and wrist and may have an MRI appearance on T1- weighted images similar to giant cell tumor of the tendon sheath, with a signal isointense to skeletal muscle. Signal intensity on T2-weighted sequences is more variable, with areas of hypo-, iso-, and hyperintensity. With gadolinium injection, enhancement can vary from minimal to marked. In this patient, however, the mass is larger and more nodular than that seen in reported cases of fibroma of the tendon sheath, which is usually < 2.5 cm in diameter and ovoid in appearance [8]. Hemangiomas have variable appearances related to the type of internal blood flow. High-flow lesions contain large, serpentine vessels that are bright on T2-weighted images but that may have flow voids, whereas slow-flow lesions have larger cystic spaces that have hyperintense signal on T2-weighted images, similar to water. Areas of intralesional fat and fibrous tissue are responsible for the heterogeneous signal seen in hemangiomas on T1-weighted sequences [9]. Clinical Management This mass in the middle finger was surgically excised (Fig. 1F), and histologic examination confirmed the diagnosis of giant cell tumor of the flexor digitorum tendon sheath. Recovery was uneventful. Commentary Giant cell tumor of tendon sheath is a slowly growing, benign tumor of the synovium that commonly presents as a painless nodular mass in the hand or wrist. Also termed localized nodular tenosynovitis, these tumors are the most common soft-tissue tumors of the hand [7, 10]. Giant cell tumor of the tendon sheath may present with either localized or diffuse forms and has a peak incidence in the third to fifth decades [7]. In its diffuse S14

3 Fig year-old man with painful swelling of middle finger. A and B, Sagittal T1-weighted spin-echo (TR/TE, 400/8) (A) and T2-weighted fat-suppressed fast spin-echo (4,040/70) (B) images through middle finger show elongated soft-tissue mass that contacts surface of flexor digitorum profundus tendon. C and D, Axial T1-weighted spin-echo (460/14) (C) and T2-weighted fat-suppressed fast spin-echo (3,720/60) (D) images of middle finger (center) at level of mid shaft of middle phalanx show mass encasing flexor digitorum profundus tendon. Only minimal amount of fluid is visible in flexor tendon sheath. (Fig. 1 continues on next page) A B C D S15

4 Liu Fig. 1 (continued) 22-year-old man with painful swelling of middle finger. E, Axial T1-weighted fast spoiled gradient-echo (18/9; flip angle, 9 ) fat-suppressed unenhanced (bottom) and contrast-enhanced (top) images of middle finger at level of mid shaft of middle phalanx show heterogeneous, mild enhancement of mass after IV gadolinium injection. This appearance is commonly seen in giant cell tumor of tendon sheath. F, Intraoperative photograph shows nodular mass being peeled off underlying flexor digitorum profundus tendon. E F form, giant cell tumor of the tendon sheath is known as pigmented villonodular synovitis (PVNS). PVNS is more likely to occur near large weight-bearing joints and can cause pressure erosions of the underlying bone [11, 12]. When presenting as a focal mass occurring in an intraarticular location, these masses are termed nodular synovitis. S16 The MRI findings in this patient are fairly characteristic of this diagnosis, with an elongated peritendinous mass of the finger composed of areas of isointensity and hypointensity relative to skeletal muscle on T2- and T1-weighted sequences. When giant cell tumor of the tendon sheath is pigmented with hemosiderin deposition, blooming may be seen on gradient-echo

5 sequences, especially when the TE is longer than 15 milliseconds [13]. Unfortunately, no gradient-echo sequences were obtained in this patient, in whom infectious tenosynovitis was the given clinical indication. Patients with giant cell tumor of the tendon sheath usually present with a painless mass but can become symptomatic if traumatized, as in this patient, when the concentrated pressure from the thin handle of a weighted plastic grocery bag resulted in acute swelling of the finger. The masses usually range from 0.5 to 3 cm in diameter and are mobile beneath the skin but attached to tendons or tendon sheaths. Histologically, these tumors are composed of multinucleated giant cells, polyhedral histiocytes, fibrosis, and hemosiderin deposits [14]. On MR images and histology, giant cell tumors of the tendon sheath may be difficult to distinguish from fibromas of the tendon sheath. Local excision of a giant cell tumor of the tendon sheath is the recommended treatment; however, the incidence of local recurrence is moderate. References 1. Erickson SJ, Cox IH, Hyde JS, Carrera GF, Strandt JA, Estkowski LD. Effect of tendon orientation on MR imaging signal intensity: a manifestation of the magic angle phenomenon. Radiology 1991; 181: Tehranzadeh J, Ter-Oganesyan RR, Steinbach LS. Musculoskeletal disorders associated with HIV infection and AIDS. Part I. Infectious musculoskeletal conditions. Skeletal Radiol 2004; 33: Azouz EM, Babyn PS, Mascia AT, Tuuha SE, Decarie JC. MRI of the abnormal pediatric hand and wrist with plain film correlation. J Comput Assist Tomogr 1998; 22: De Beuckeleer L, De Schepper A, De Belder F, et al. Magnetic resonance imaging of localized giant cell tumour of the tendon sheath (MRI of localized GCTTS). Eur Radiol 1997; 7: Jelinek JS, Kransdorf MJ, Shmookler BM, Aboulafia AA, Malawer MM. Giant cell tumor of the tendon sheath: MR findings in nine cases. AJR 1994; 162: Yacoe ME, Bergman AG, Ladd AL, Hellman BH. Dupuytren s contracture: MR imaging findings and correlation between MR signal intensity and cellularity of lesions. AJR 1993; 160: Kransdorf MJ, Murphey MD. Synovial tumors. In: Kransdorf MJ, Murphey MD, eds. Imaging of soft tissue tumors. Philadelphia, PA: Saunders, 1997: Fox MG, Kransdorf MJ, Bancroft LW, Peterson JJ, Flemming DJ. MR imaging of fibroma of the tendon sheath. AJR 2003; 180: Vilanova JC, Barcelo J, Smirniotopoulos JG, et al. Hemangioma from head to toe: MR imaging with pathologic correlation. RadioGraphics 2004; 24: Monaghan H, Salter DM, Al-Nafussi A. Giant cell tumour of tendon sheath (localised nodular tenosynovitis): clinicopathological features of 71 cases. J Clin Pathol 2001; 54: Karasick D, Karasick S. Giant cell tumor of tendon sheath: spectrum of radiologic findings. Skeletal Radiol 1992; 21: Rodrigues C, Desai S, Chinoy R. Giant cell tumor of the tendon sheath: a retrospective study of 28 cases. J Surg Oncol 1998; 68: Port JD, Pomper MG. Quantification and minimization of magnetic susceptibility artifacts on GRE images. J Comput Assist Tomogr 2000; 24: Al-Qattan MM. Giant cell tumours of tendon sheath: classification and recurrence rate. J Hand Surg [Br] 2001; 26:72 75 S17