Soft Tissue Mass of the Second Toe in an 11-Year-Old Boy

CASE HISTORY An otherwise healthy 11-year-old boy presented to the authors’ institution for evaluation of a soft tissue mass on the dorsum of the right second toe. The family reported that the mass had grown progressively for the past 6 months. The patient denied pain or functional limitations. The patient’s mother had an uncomplicated, full-term pregnancy. The patient was the third of four children. The patient had no surgeries or previous injuries to the affected area. There was no family history of similar lesions. Physical examination revealed a firm mass located in the extensor surface of the distal interphalangeal joint of the right second toe, not yet reaching the border of the nail. The mass was tender to palpation. The toe was warm, pink, and had brisk capillary refill. Light touch sensation was intact throughout the right foot. Passive toe flexion elicited minimal pain. The patient was able to do heel and toe walking. Examination of the rest of the body was unremarkable; no other masses, skin markings, or toe anomalies were found. The patient’s complete blood count was normal. Radiographs (Fig 1) and magnetic resonance imaging (MRI) scans (Fig 2) were obtained.Fig 1.: Lateral view of the great toe.Fig 2A–B.: (A) Sagittal T1-weighted MRI scan. (B) Sagittal T2-weighted MRI scan.Based on the history, physical findings, and imaging studies, what is the differential diagnosis? RADIOGRAPHIC INTERPRETATION Plain radiographs (Fig 1) of the great toe showed soft tissue swelling of the digit. There were lucent areas with well-defined margins along the ventral surface of the distal end of the proximal phalanx and the proximal end of the distal phalanx (arrows). An MRI scan (Fig 2) revealed a soft tissue mass that appeared to extend through the interphalangeal joint with involvement of the underlying bone. On a T1-weighted image, the lesion was intermediate in signal intensity (curved arrows) with erosion of the proximal (long arrow) and distal (short arrow) phalanges. On a T2-weighted image, the mass was high in signal intensity (curved arrows), extending through the joint space between the proximal (long arrow) and distal (short arrow) phalanges with erosion of the underlying bone. The tumor was not dark on T2-weighted images. The erosions on both sides of the joint suggest joint disease (intraarticular or adjacent tendon sheath) rather than a primary bone lesion. DIFFERENTIAL DIAGNOSIS Fibroma Giant cell tumor Pigmented villonodular synovitis (giant cell tumor of tendon sheath) Synovial sarcoma Digital fibromatosis Granuloma annulare Septic arthritis Inflammatory arthropathy An excisional biopsy was done, and the histologic picture is shown in Figure 3.Fig 3A–B.: (A) Hematoxylin and eosin stain photomicrograph (×20). (B) Gomori’s stain photomicrograph (×40).Based on the history, physical findings, radiographic studies, and histologic picture, what is the diagnosis, and how should this patient be treated? HISTOLOGY The tumor cells are arranged in extensive sheets or compact nests of mononuclear cells with a variable content of multinucleated giant cells (arrow, Fig 3A). The predominant cell is polyhedral, with an oval nucleus and faintly eosinophilic cytoplasm. The multinucleated giant cells resemble osteoclasts. Fibroconnective tissue permeates between individual cells and clusters. Hyalinized connective tissue is a prominent feature in less cellular areas. Hemosiderin laden macrophages are scattered (arrows, Fig 3B). Foamy cells are inconspicuous. DIAGNOSIS Pigmented villonodular synovitis TREATMENT AND DISCUSSION The lesion was removed surgically, and the gross specimen revealed yellow-brown tissue with areas of hemosiderin. The tumor seemed to originate from the joints and had eroded the bones of the distal phalanx, proximal phalanx, and had extensive soft tissue involvement. The extensor tendon was freed of tumor and a radical removal of the soft tissue was done. The postoperative course was uneventful. Pigmented villonodular synovitis is a benign growth of the synovial lining, characterized by a diverse cell population, embedded in a collagenous matrix, including round or polygonal stromal cells, multinucleated giant cells, foam cells, and hemosiderin containing cells. As reported by Byers et al, 2 this condition first was described in 1852 as cancer originating in the flexor tendon sheath of the middle and index fingers. Pigmented villonodular synovitis is just one of many clinical names given to this type of tumor. Other names include giant cell tumor of the tendon sheath, hemosiderotic synovitis, tenosynovial giant cell tumor, nodular tenosynovitis, benign synovioma, xanthoma, myeloxanthoma, villous arthritis, and sclerosing hemangioma. 2,15 In 1941, Jaffe et al 8 described the synovium of the tendon sheath, the bursa, and the joint as one anatomic unit. They concluded that nomenclature differences referred to multiple manifestations of pigmented villonodular synovitis, because of variations in clinical presentation, such as location and number of tumors within this unit. These lesions may appear as one or more discrete nodular masses in the synovium of the tendon sheaths or small joints of the fingers and toes. Less frequently, they occur as diffuse tumors of the knee. 6,7 Ushijima and colleagues, 19 in a study of 207 cases of pigmented villonodular synovitis, reported 183 lesions of the digits (the majority involving the fingers), 10 lesions of the ankle, and eight lesions occurring in the knee. Rodriques et al 15 reviewed 28 patients and found 20 cases of localized, small joint tumors (fingers and toes), and eight cases of diffuse, large joint tumors (knee, ankle and foot, wrist, and elbow). These authors described the gross appearance of the digit tumors as multiple, small, variegated masses surrounded by a thin fibrous capsule, whereas the large joint tumors were more robust and covered by one or more layers of synovium. Rao and Vigorita 13 reported the association of fibrosis with pigmented villonodular synovitis, but found no relationship between the progressive extent of fibrosis and the duration of symptoms. Pigmented villonodular synovitis does not metastasize but may be invasive locally (local bone involvement). Scott 18 proposed invasion of villonodular tissue growth into the vascular foramina, along side the nutrient vessels, but carrying its own blood supply from the intraosseous membrane. Deep penetration may cause intraosseous cysts because of pressure atrophy. In support of this, he reported cyst origination in areas of numerous vascular foramina, as occurred in the current case. Chung and Janes 3 described an osteoporotic mechanism of bone invasion, whereby tumor proliferation initiates a cascade of increased intraarticular pressure, superficial cystic degeneration, and cystic wall fracture, allowing access to the bone. Invasion through the articular cartilage and cortex at the chondroosseous junction also is a possibility. 12 The etiology of pigmented villonodular synovitis has yet to be elucidated. Jaffe et al 8 suggested that pigmented villonodular synovitis is an inflammatory response to an unknown agent. Trauma also has been considered because of serosanguineous joint fluid and the presence of intracellular and extracellular hemosiderin in the synovial membrane. 12 Fisk 5 proposed the etiology of repeated minor trauma to the synovial fringes with consequent hydrarthrosis. Young and Hudacek, 20 also favoring trauma as the most probable cause, produced lesions similar to pigmented villonodular synovitis after repeated injections of blood into the knees of canines. However, only a small percentage of patients in large scale studies present with a history of trauma. 15,19 In a recent review of 44 tenosynovial giant cell tumor specimens, Sciot et al 17 found a high frequency of similar clonal chromosomal aberrations in the localized and diffuse forms of the disease. This suggests that the disease is most likely neoplastic rather than an inflammatory or traumatic reaction. Age of onset is predominantly between the third and fifth decades, 3,11,12,14,15 but has been observed to occur as early as the end of the first or the beginning of the second decade. 11,13,15 The preponderance of patients are female. 3,11,13,15 The time from initial onset of symptoms to diagnosis is variable. Several authors reported an average of 27 to 30 months. 13,14,19 Chung and Janes 3 defined a range of 2.5 to 11 years, whereas Rodrigues et al 15 reported a range of 6 weeks to 3 years with an average of 6 months. Clinical presentation consists of a palpable mass with a history of size progression. Palpation tenderness or pain with movement of the joint are infrequent symptoms. 11,15,19 Digit lesions most often occur adjacent to the interphalangeal joint, yet are unrestricted with respect to flexor, extensor, lateral or circumferential locations. 4 Radiographs show a slightly opaque soft tissue mass, and computed tomography (CT) scans reveal the presence of bone invasion well, if present. 14 Magnetic resonance imaging best shows the presence of the soft tissue mass; lesions have decreased signal intensity on T1- and T2-weighted images because of the deposition of hemosiderin. 9 Color variation in these lesions ranges from brown to yellow. 3,13,18 Brown is suggestive of iron deposition, whereas yellow is associated with lipid accumulation. 13 Histologic and radiologic evaluation helps to distinguish pigmented villonodular synovitis from other lesions included in the differential diagnosis. Fibroma of the tendon sheath and synovial sarcoma lack foam cells, siderophages, and multinucleated giant cells as seen in pigmented villonodular synovitis. 10,19 The presence of nodules containing multinucleated giant cells rules out hemosiderotic synovitis. 13 The presence of a soft tissue mass helps to rule out septic arthritis and inflammatory arthropathy. Also, the scalloped-out area with well-defined sclerotic margins as found in pigmented villonodular synovitis differs from the diffuse demineralization and ill-defined margins that are seen on the plain radiographs of a patient with septic arthritis. Standard treatment includes complete tumor removal. Excision extent depends on the aggressiveness of the lesion. Patients with localized, small joint tumors require minimal joint disruption, whereas patients with widespread, large joint tumors may necessitate total synovectomy or amputation. Whenever possible, as much of the synovium should be spared to prevent joint disability and decrease stiffness postoperatively. 13 Recurrence, attributed to incomplete excision, has been reported in approximately 28% to 35% of patients. 14–16 Kotwal et al 11 implicated the use of radiotherapy to prevent recurrence but defined an at-risk population to be patients with possible incomplete excision, tumors with mitotic figures, or bone involvement. The authors do not recommend the use of radiotherapy for cases similar to the current case because of risks of damaging growing physes or causing radiation-induced soft tissue changes (neuritis or vasculitis) or malignant transformation. 1 The patient currently is asymptomatic 12 months after surgery and has full range of motion, intact neurovascular status, and no sign of recurrence.