Thigh Mass in a 9-Year-Old Boy
Year: 2004
Type: article
Study design: Case Report
Abstract: LEARNING OBJECTIVES On completion of this study, the reader should: recall the histologic spectrum of benign vascular malformations or hemartomas; plan a treatment algorithm that begins with benign basic therapy in the form of compression and later progresses to include sclerotherapy, radiotherapy, and surgical excision. HISTORY AND PHYSICAL EXAMINATION A 9-year-old boy reported a painless right thigh mass for 3 months before presenting to the authors’ institution. The patient’s parents reported episodes of intermittent limping, but no other signs or symptoms. The patient had been admitted to another institution for evaluation, where plain radiographs and MRI scans were taken. Magnetic resonance imaging scans revealed a soft tissue mass in the right distal thigh, and the patient was referred to the authors’ institution for additional evaluation. The patient otherwise was healthy during the past several months, with no evidence of weight loss, fatigue, fever, sweats, chills, nausea, vomiting, or other constitutional symptoms. His medical history was notable for Grade V vesicoureteral reflux that was corrected by surgical reimplantation of the ureters at 9 months of age. The patient was the product of a full-term, uncomplicated pregnancy, and his developmental and family histories were noncontributory. On physical examination, the patient was a slim, healthy appearing boy. His gait was normal. The patient had full ROM of the right hip and knee, with no pain on passive or active motion. A soft tissue mass was present on the anterolateral aspect of the right distal thigh, in the area of the vastus lateralis muscle. The mass was of moderate size (3 × 5 × 3 cm), soft, mildly tender to palpation, mobile, and deep-seated. There was no erythema, increased warmth, or swelling over the area of the mass. Neurovascular examination was normal. His abdomen was soft and nontender without masses or hepatosplenomegaly. Bilateral inguinal lymphadenopathies were observed. The remainder of the physical examination was normal. Plain radiographs of the patient’s right distal thigh were normal, without evidence of a soft tissue mass. The MRI scans of the patient’s right distal thigh are shown in Figures 1 through 4. Fig 1.: Coronal T1-weighted image of the right distal thigh.Fig 2.: Axial T2-weighted image of the right distal thigh.Fig 3.: Sagittal short tau inversion recovery (STIR) image of the right distal thigh.Fig 4.: Coronal post-gadolinium T1-weighted image of the right distal thigh.Based on the history, physical findings, and imaging studies, what is the differential diagnosis? RADIOGRAPHIC INTERPRETATION The coronal T1-weighted MRI scan (Fig 1) of the right distal thigh shows a well-circumscribed, ovoid intramuscular mass within the vastus lateralis muscle. The mass is mildly hyperintense relative to muscle. On the axial T2-weighted image (Fig 2) the mass is hyperintense, with multiple tiny intralesional foci of relatively low signal intensity. Well-circumscribed margins again are seen. The sagittal short tau inversion recovery (STIR) image (Fig 3) also shows a hyperintense mass (M). A vitamin E capsule (C) was placed on the skin overlying the region of palpable abnormality, which corresponds to the observed mass. After intravenous administration of gadolinium-diethylenetriamine pentaacetic acid, the coronal T1-weighted image (Fig 4) revealed a heterogeneous enhancement pattern. No discrete septations or fluid-fluid levels are appreciated, and the adjacent cortex and marrow of the lateral distal femur shows no associated abnormalities. DIFFERENTIAL DIAGNOSIS Vascular malformation (venous, arterial, arteriovenous, capillary, lymphatic) Hemangioma Fibrosarcoma Rhabdomyosarcoma Synovial cell sarcoma After presentation to the authors’ institution, an incisional biopsy with an intraoperative frozen section was done. The photomicrographs are shown in Figs 5 and 6. Fig 5.: Low power photomicrograph of the lesion (Stain, hematoxylin and eosin; magnification, ×100).Fig 6.: High power photomicrograph of the lesion (Stain, hematoxylin and eosin; magnification, ×400).Based on the history, physical findings, radiographic studies, and histologic pictures, what is the diagnosis and how should this lesion be treated? See page 304 for diagnosis and treatment. Continuation of ORP Conference from page 303. HISTOLOGY INTERPRETATION The specimen consisted of multiple fragments of rubbery tan soft tissue. Histologic examination revealed a sponge-like proliferation of dilated vascular channels within skeletal muscle, separated by thin fibrous septae (Fig 5). Some of the spaces contained red blood cells, other spaces were empty, and some spaces contained organized thrombi. The dilated spaces were lined by flattened endothelial cells (Fig 6). Scattered chronic inflammatory cells (lymphocytes) were present in the interstitium. DIAGNOSIS Vascular malformation, lymphangioma TREATMENT AND DISCUSSION The clinical, radiographic, and pathologic findings in this case were consistent with the diagnosis of lymphangioma. The differential diagnosis of lymphangioma can include other vascular anomalies, benign soft tissue tumors, and soft tissue sarcomas that occur in the pediatric population.15 Radiographically, lymphangiomas may be differentiated from soft tissue sarcomas in pediatric patients (fibrosarcoma, rhabdomyosarcoma, synovial cell sarcoma) on the basis of invasion of local structures. Lymphangiomas tend to be noninvasive, whereas sarcomas tend to be invasive, destroying the normal tissues around them. In the current case, soft tissue sarcomas ultimately were ruled out on biopsy, based on the lack of a solid tumor component with malignant spindle cell features (hypercellularity, mitotic figures, significant cellular pleomorphism). Hemangioma and the other vascular malformations also were ultimately ruled out based on the histologic findings, but MRI provided some helpful clues.7,15,17–19,21,22 Lymphangiomas with hemorrhage and/or thrombi, as seen in the current patient, can be confused with cavernous hemangiomas.22 However, the spongelike architecture of the lesion, with gaping vascular spaces lined by thinned endothelium, in a lymphoid-rich background would favor a diagnosis of lymphangioma over hemangioma. Venous malformations may have a similar presentation to lymphangiomas clinically and radiographically, and often are associated with lymphatic malformations, but in isolation these lesions will not show evidence of significant lymphoid tissue on histologic examination. Arterial and arteriovenous malformations similarly will not have evidence of significant lymphoid tissue on histologic examination. These lesions also tend to be high flow lesions and show low intensity on T2-weighted MRI scans and flow voids, unlike lymphangiomas, which are low flow and hyperintense on T2-weighted images. Capillary malformations usually are located in the dermis, rather than deeper and intramuscularly as in the current patient. As reported by Mulliken et al,18 the term, lymphangioma, first was coined in the nineteenth century by Wegener, a student of Virchow. Its use has continued into the twentieth century, but confusion has arisen over what terms are appropriate to describe lymphatic anomalies. This confusion was, in part, caused by the unclear etiology of lymphagiomas. These lesions always are benign, and now are generally considered to be developmental malformations.22 Evidence seems to support this etiology.11,23 Lymphangiomas are thought to arise from lymphatic tissue that fails to communicate normally with the lymphatic system and therefore becomes sequestered. This tissue then may proliferate and accumulate fluid producing a mass or cystic lesion.22 The few lymphangiomas that are not the result of developmental malformations are attributable to secondary causes that produce lymphatic channel obstruction, such as inflammation and fibrosis that occur after surgery, after infection, or after radiation exposure.8,9,20 As a developmental lesion, lymphangiomas are considered to be a type of vascular malformation based on the classification system of Mulliken and Glowacki,19 a model proposed in 1982 to clarify the nomenclature of vascular anomalies and allow for better understanding of the etiology and treatment of vascular anomalies. This system divides vascular anomalies into two groups: (1) hemangiomas, which are neoplastic lesions with endothelial hyperplasia; and (2) vascular malformations, which are developmental lesions with normal endothelial turnover.21 Vascular malformations are subclassified by the predominant vessel found in the lesion (venous, arterial, capillary, lymphatic, mixed) and by the blood flow within the lesion (high versus low flow).15 Under this classification, the term lymphangioma is a misnomer because, like the term hemangioma, it refers to a tumor or neoplasm, rather than a malformation.14 The more appropriate term is lymphatic malformation. There has been a push in recent years to adopt this terminology, but the term lymphangioma still is used commonly.14,15 Lymphangiomas traditionally have been separated into three categories based on the size of their lymphatic spaces: capillary lymphangiomas (smallest), cavernous lymphangiomas, and cystic lymphangiomas or cystic hygromas (largest). These three terms, however, may simply represent a spectrum of one group of lesions. In addition, many lymphangiomas have cystic and cavernous components.22 Lymphangiomas alternately have been classified as microcystic, macrocystic, or combined.18 Lymphangioma is a rare pediatric lesion unlike hemangioma, the most common soft tissue tumor of infancy and childhood.19 An equal gender ratio usually is reported for lymphangiomas, although a slight male predominance occasionally is seen.2,22 Approximately 50% to 65% of lesions are present at birth, with 90% estimated to be present by the end of the second year of life.1,2,4,5,10 The lesions can arise later in childhood and adulthood, with some studies reporting as many as ⅓ of cases arising in adults.22 Although lymphangiomas may arise in any part of the body containing lymphatics, three regions, the head, neck, and axilla, account for 50% to 75% of the lesions, with the neck being the most common site.2,15 A lower extremity location, as seen in the current patient, is relatively less common. One study found that such lesions account for approximately 5% of all lymphangiomas.2 Lesions that present in adulthood, rather than the more common childhood appearance, typically are superficial cutaneous lymphangiomas.8,20 Internal organs that may have lymphangiomas develop include the lungs, gastrointestinal tract, spleen, liver, and bone. Lymphangiomas of the spleen, liver, and bone often occur as part of diffuse or multifocal disease, termed lymphangiomatosis.22 Lymphangiomas of the extremities usually present as a painless, palpable soft tissue mass, as seen in the current patient. The mass may enlarge, remain stable, or wax and wane in size with time.22 Patients also may have mild lymphedema develop at the extremity site, or more massive edema with subsequent skeletal and soft tissue overgrowth.15,18 Other signs and symptoms depend on the location of the lesion or complications of the lesion. The two most common and major complications of an untreated lymphangioma are intralesional bleeding (either spontaneous or secondary to trauma) and infection. Episodes of infection in lymphangiomas may result in cellulitis or lymphangitis.18 Occasionally, rapid enlargement of head and neck lymphangiomas may be triggered by an upper respiratory tract infection that obstructs the lymphatics draining the tumor. These lesions may then lead to airway and feeding problems.22 Lymphangiomas can be recognized and assessed radiographically via MRI and ultrasound. Plain radiographs are less helpful, and CT scanning is inferior to MRI, as it is in the evaluation of all soft tissue lesions. Magnetic resonance imaging generally is considered the radiographic test of choice.18,19 Lymphangiomas are hyperintense on T2-weighted sequences because of their high water content and, conversely, of low or intermediate intensity on T1-weighted images. A variable response occasionally can be seen on T1- and T2-weighted images. The lesions are slow flow with no flow voids, as opposed to the high blood flow states and flow voids seen in arteriovenous malformations.19 Macrocystic lesions or lesions with large lymphatic spaces often have fluid levels because of the presence of protein or blood. Gadolinium contrast administration usually causes enhancement of septations and the rims of large cysts within lymphangiomas. The contents of small cysts also can enhance, particularly if there is intralesional bleeding present.18 In addition, MRI often shows large and/or anomalous venous channels within the lesion.3 Magnetic resonance lymphangiography also can detect lymphangiomas, particularly those found in the extremities, by showing the dilated and interrupted lymphatic channels.13 Ultrasound can be an excellent tool in the detection of macrocystic lymphangiomas.18 Grossly, the appearance of lymphangiomas may vary from well-circumscribed lesions consisting of large interconnecting cysts, as seen in cystic lymphangiomas, to ill-defined, spongelike compressible lesions composed of microscopic cysts, as seen in cavernous lymphangiomas. Lesions often present with features consistent with both of these extremes. Cavernous lymphangiomas do not have the large lymphatic spaces of cystic lymphangiomas because they arise in areas where dense connective tissue and muscle prevent expansion. Regardless of the classification, all lymphangiomas share several histologic features in common. The lymphatic spaces of the lesions are lined with an attenuated endothelium of variable thickness resembling that seen in normal lymphatics. Smaller lymphatic spaces only have a thin adventitia surrounding them, whereas large lymphatic spaces contain an adventitia and a partially developed smooth muscle layer.22 The lymphatic spaces of a lymphangioma typically are filled with eosinophilic, protein-rich fluid containing lymphocytes, lipid droplets, and, occasionally, erythrocytes.16,18,22 The stroma consists of a meshwork of collagen dotted with small lymphoid aggregates. It can become inflamed, edematous, and finally fibrotic if the lymphangioma is infected repeatedly.22 Although lymphangiomas may occur as solitary lesions, it is not uncommon to find them associated with other vascular malformations, such as capillary, venous, and arteriovenous malformations.6,19 Although lymphangiomas are considered benign lesions, they are capable of producing morbidity because of their size, anatomic location, and potential complications. With such morbidity and because lymphangiomas rarely spontaneously regress, most of these lesions ultimately require definitive treatment.22 Currently, preferred treatment for symptomatic lesions is surgical reduction or excision. Surgery is potentially curative, but total excision of the mass is not always possible.18 The degree of surgical removal is determined by tumor makeup, anatomic location, and the attempt to achieve a reasonable cosmetic result. Complete excision and a low rate of local recurrence typically are achieved with cystic lymphangiomas, for example, because of their tendency to be well-circumscribed and superficial. Cavernous lymphangiomas, however, often infiltrate between muscle fibers, making complete excision difficult, and increasing the likelihood of local recurrence and other complications, such as nerve palsies.22 The reported recurrence rates for patients with lymphangiomas are as much as 40% after incomplete excision and 17% after macroscopically complete excision.1 Recurrence is secondary to regrowth of microcystic lymphatic channels that were missed on excision.18 Compression garments are the mainstay of treatment before surgery when chronic lymphedema, skin breakdown, and skeletal and soft tissue overgrowth are present. When these fail, surgery should be considered.15 Other nonsurgical treatments that have been used include sclerosing agents and radiation treatment. Sclerosing agents, such as 100% ethanol, can shrink the lesion, but should not be used as curative alternatives to surgery. Sclerotherapy is more effective in macrocystic lesions and may be used in anatomic regions that are difficult to approach surgically.18 Radiation has yielded poor results and malignant transformation of previously irradiated lymphangiomas has been documented.12 The treatment of the current patient included the current standard of care for lymphangiomas. After incisional biopsy and intraoperative frozen section, surgical excision of the lesion was done. The soft tissue lesion seemed to be confined to the right distal vastus lateralis muscle, with no evidence of extension into adjacent tissues, such as the overlying fat or underlying bone, allowing for the possibility of complete excision with wide surgical margins. Final, complete histologic analysis of the lesion proved to be consistent with lymphangioma. At the 1-year followup, the patient was completely asymptomatic, with full ROM of the right hip and knee and no neurologic or vascular deficits in the lower extremity. There was no evidence of a recurrent or residual right distal thigh mass. Lymphangioma or lymphatic malformation is a relatively less common form of vascular malformation encountered in the pediatric population and may involve the musculoskeletal system. It is important to be aware of the common clinical and radiographic findings in this and other vascular anomalies because these lesions may be difficult to distinguish from other malignant musculoskeletal tumors, such as soft tissue sarcomas, on initial presentation. Magnetic resonance imaging is a valuable tool in the differential diagnosis of lymphangiomas, but definitive diagnosis often is not possible until a pathologic specimen has been obtained. Lymphangiomas, similar to other vascular malformations, seldom spontaneously regress and, thus, often require surgical intervention. The treatment of choice is surgical reduction or excision. The possibility of complete excision depends on the characteristics of the particular lesion and recurrence is greatly reduced when complete excision is achieved.
Language: English
Subfield: Surgery
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W1969767277