Septum-like structures in lipoma and liposarcoma: MR imaging and pathologic correlation

The Growth Factors of Subcutaneous Benign Lipoma: Consideration from Anatomical Position of Occurrence

Subcutaneous lipomas are the most common benign soft-tissue tumors. Theoretically, adipocyte sites could be the primary foci; however, lipomas are likely located in the occipital, neck, shoulder, torso, and thigh areas. To date, no study has reported the anatomical relationship between these subcutaneous structures and lipomas. Therefore, we aimed to investigate the anatomical locations of lipomas and considered their growth factors. In addition, we discussed the mechanism of fat amplification to improve the success of fat grafting.

METHODS

In the present study, lipomas measuring more than 5 cm in diameter from patients hospitalized between 2017 and 2021 were retrospectively examined using preoperative computed tomography and magnetic resonance imaging as well as clinical records with intraoperative pictures.

RESULTS

In total, 22 lipomas of 22 patients were examined. All lesions (100%) were accompanied by neurovascular perforators. Nineteen lesions (86%) were located deep in the superficial fascia, where it was clearly defined. Moreover, all lesions were located at the mobile adipofascial layer adjacent to an anchored fixed or less mobile structure.

CONCLUSIONS

Lipoma growth might require neurovascular perforators that supply both blood flow and continuous stretching stimuli. The mobile adipofascial layer with bones adjacent to a fixed or less mobile area might also be necessary to grow lipomas. If these findings can be used as clues to elucidate the mechanism of fat amplification in the future, it may lead to an improvement in the survival rate of fat grafts.

Lipoma and Its Doppelganger: The Atypical Lipomatous Tumor/Well-Differentiated Liposarcoma

Lipomatous tumors are among the most common soft tissue lesions encountered by the general surgeon. Shared history and clinical presentation make differentiation between benign lipomas and low-grade liposarcomas a diagnostic dilemma. This article reviews the epidemiology, clinical history, diagnostic workup, management, natural history, and surveillance of benign lipomas and atypical lipomatous tumors/well-differentiated liposarcomas. Although it is important that aggressive, potentially malignant atypical lipomatous tumors and liposarcomas be managed in a multidisciplinary, preferably high-volume setting, it is equally as important for the nonspecialist general surgeon to be familiar with lipoma and its doppelganger-the well-differentiated liposarcoma.

Giant lipoma of the tongue: A case report and review of the literature

This report presents the case of a 49-year-old man who presented with giant masses that had recently grown on the bilateral sides of the tongue. A clinical examination revealed rubbery yellowish lesions protruding from the tongue. A panoramic radiograph showed an enlarged soft tissue shadow of the tongue. Computed tomography showed well-defined circumscribed mass exhibiting a homogeneous low density on the bilateral sides of the tongue. On magnetic resonance images, the masses showed a high signal intensity on T1-weighted images and iso-signal intensity with partially hyperintense margin on fat-suppressed T2-weighted images. Surgical excision was performed, and a histopathologic examination confirmed the diagnosis of lipoma. The patient recovered well with no sign of recurrence. A giant lipoma is defined as a lipoma larger than 5 cm in diameter. A literature review of giant lipomas of the tongue is also presented herein.

Imaging of Soft Tissue Tumors

Differentiation of malignant from benign soft tissue tumors is challenging with imaging alone, including that by magnetic resonance imaging and computed tomography. However, the accuracy of this differentiation has increased owing to the development of novel imaging technology. Detailed patient history and physical examination remain essential for differentiation between benign and malignant soft tissue tumors. Moreover, measurement only of tumor size based on Response Evaluation Criteria In Solid Tumors criteria is insufficient for the evaluation of response to chemotherapy or radiotherapy. Change in metabolic activity measured by ¹⁸F-fluorodeoxyglucose positron emission tomography or dynamic contrast enhanced-derived quantitative endpoints can more accurately evaluate treatment response compared to change in tumor size. Magnetic resonance imaging can accurately evaluate essential factors in surgical planning such as vascular or bone invasion and "tail sign". Thus, imaging plays a critical role in the diagnosis and treatment of soft tissue tumors.

CT and MRI features of tumors and tumor-like lesions in the abdominal wall

Masses involving the abdominal wall are common in clinical practice and have many etiologies, including tumors and tumor-like lesions. Abdominal wall tumors include primary and secondary tumors, the former of which constitute a heterogeneous group of soft tissue tumors with their own unique spectrum. Tumor-like lesions, such as hernias, are more common and must be distinguished from true tumors. Medical imaging is valuable for discovering, diagnosing, and evaluating the extent of abdominal wall masses. With the increasing application of computed tomography (CT) and magnetic resonance imaging (MRI), determining a diagnosis or narrowing the differential diagnosis is often possible, thus facilitating effective management. In this article, we comprehensively review the spectrum of common abdominal wall masses and present the CT and MRI features of typical cases in our hospital. A systematic stepwise diagnostic approach is also proposed for clinical practice.

The role of surgical margins in atypical Lipomatous Tumours of the extremities

Background

Atypical lipomatous tumours (ALT) are common adipocytic tumours. Due to their large size and deep-seated location, wide resection might result in severe functional deficits. The question which margins should be aimed is hence discussed controversially.

Methods

Forty consecutive patients underwent limb-sparing resections. Margins were defined as R0 (wide resection), R1 (marginal resection) or R2 if tumour was left. All patients were followed for evidence of local recurrence or remote metastases. Overall and recurrence-free survival was calculated.

Results

The mean age at the time of surgery was 61.9 years. The mean tumour diameter was 17 cm with no patient having metastatic disease. In 8 cases a wide (R0) resection, in 31 cases a marginal (R1) and in one patient a R2-resection was performed. The median follow-up time was 40 months. Four patients died due to causes that were not tumour-related. 3 (7.5%) patients (all R1) developed local recurrences. Two of our 3 recurrences in this series occurred in 6 already recurring cases. We observed no dedifferentiation of tumours and no metastatic disease.

Conclusions

ALT represents a comparatively common diagnosis in large deep-seated lesions of the extremities, especially in patients over 60 years. Marginal resection shows an acceptable rate of local recurrence. The risk of dedifferentiation as proven also in a metaanalysis of the English literature of the last 30 years is close to 1%, metastatic disease is exceedingly rare.

The management of deep-seated, lowgrade lipomatous lesions

Deep-seated, low-grade lipomatous lesions detected on imaging often cause uncertainty for diagnosis and treatment. Confidently distinguishing lipomas from well-differentiated liposarcomas is often not possible on imaging. The approach to management of such lesions varies widely between institutions. Applying an evidenced-based approach set around published literature that clearly highlights how criteria such as lesion size, location, age and imaging features can be used to predict the risk of well-differentiated liposarcomas and subsequent de-differentiation would seem sensible. Our aim is to review the literature and produce a unified, evidence-based guideline that will be a useful tool for managing these lesions.

Imaging Evaluation of Malignant Chest Wall Neoplasms

Neoplasms of the chest wall are uncommon lesions that represent approximately 5% of all thoracic malignancies. These tumors comprise a heterogeneous group of neoplasms that may arise from osseous structures or soft tissues, and they may be malignant or benign. More than 50% of chest wall neoplasms are malignancies and include tumors that may arise as primary malignancies or secondarily involve the chest wall by way of direct invasion or metastasis from intrathoracic or extrathoracic neoplasms. Although 20% of chest wall tumors may be detected at chest radiography, chest wall malignancies are best evaluated with cross-sectional imaging, principally multidetector computed tomography (CT) and magnetic resonance (MR) imaging, each of which has distinct strengths and limitations. Multidetector CT is optimal for depicting bone, muscle, and vascular structures, whereas MR imaging renders superior soft-tissue contrast and spatial resolution and is better for delineating the full extent of disease. Fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT is not routinely performed to evaluate chest wall malignancies. The primary functions of PET/CT in this setting include staging of disease, evaluation of treatment response, and detection of recurrent disease. Ultrasonography has a limited role in the evaluation and characterization of superficial chest wall lesions; however, it can be used to guide biopsy and has been shown to depict chest wall invasion by lung cancer more accurately than CT. It is important that radiologists be able to identify the key multidetector CT and MR imaging features that can be used to differentiate malignant from benign chest lesions, suggest specific histologic tumor types, and ultimately guide patient treatment. (©)RSNA, 2016.

Recurrence After Marginal Excision for Atypical Lipomatous Tumors Versus Lipomas of the Extremities

This study reviewed the medical records of 90 patients with lipomas (47 patients) and atypical lipomatous tumors (ALT)/well-differentiated liposarcomas (WDL) (43 patients) of the extremities treated from 2006 to 2012. All patients had preoperative biopsy and postoperative histologic analysis of the tumors; surgical margins were marginal in all cases. Histologic sections of the tissue blocks from the excised specimens were re-reviewed for all patients; a consensus with postoperative histologic analysis was confirmed. Molecular chromosome analysis was performed on fluorescence in situ hybridization in tissue sections from the tissue blocks in all cases for the purpose of this study; a ratio greater than 2 was considered to represent murine double-minute 2 (MDM2) amplification consistent with a diagnosis of ALT/WDL. Mean follow-up was 52 months (range, 14-96 months). Local recurrence and metastasis rates and the relationship of patient age and sex with tumor size and location were evaluated. None of the patients with lipomas experienced local recurrence compared with 6 patients (13.9%) with ALT/WDL who experienced local recurrence within a mean of 48 months (range, 33-96 months); this difference was statistically significant. None of the patients in either group experienced metastasis prior to the study period. Local recurrence did not correlate statistically with patient age or sex, or with tumor size or location. [Orthopedics. 2016; 39(4):e610-e614.].

Intramuscular lipoma: a review of the literature

Lipomas are the most common type of soft tissue mesenchymal tumors. They are typically located subcutaneously and consist of mature fatty tissue. When they occur under the enclosing fascia, they are called deep-seated lipomas. Infrequently, lipomas can arise inside the muscle and are called intramuscular lipomas. Intramuscular lipomas have been commonly investigated and categorized in the same group as other deep-seated and superficial lipomatous lesions. Their clinical, histological and imaging characteristics may resemble well-differentiated liposarcomas, further adding to the difficulties in the differential diagnosis. This article summarizes the available literature and describes the typical epidemiological, pathological and clinical features of intramuscular lipomas, as well as delineating their treatment and prognosis.

MRI characteristics of lipoma and atypical lipomatous tumor/well-differentiated liposarcoma: retrospective comparison with histology and MDM2 gene amplification

PURPOSE

To review the reliability of MR imaging features for the purpose of distinguishing lipoma and atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL).

MATERIALS AND METHODS

A retrospective review of 87 patients with histologically proven lipomatous tumors was performed. All underwent MR imaging, assessing lipomatous content, septation, and nodules. The associations between these features and tumor diagnosis based on morphology and the presence or absence of MDM2 amplification were explored. The age of the patient and the size and location of the lesion were also recorded for statistical analysis.

RESULTS

Of the 87 patients, 54 were classified as lipomas and 33 as ALT/WDL. MR identified ALT/WDL with a sensitivity of 90.9 % (CI 74.5-97.6) and a specificity of 37.0 % (CI 24.6-51.3). The positive and negative predictive values were 46.9 % (CI 34.5-59.7) and 86.9 % (CI 65.3-96.6), respectively. The mean age of patients with ALT/WDL was greater (60 years [range 40-83 years]) than those with lipoma (52 years [range 10-79 years]) (p = 0.025). The mean size of ALT/WDL (18.7 cm [range 5-36 cm]) was significantly greater than lipoma (13.9 cm [range 3-32 cm]) (p = 0.003). Features that increased the likelihood of ALT/WDL included: patient age over 60 years, maximal lesion dimension over 10 cm, location in lower limb, and presence of non-fatty areas, by a factor of 2.61-6.25 times.

CONCLUSIONS

ALT/WDL and lipoma have overlapping MR imaging characteristics. The most reliable imaging discriminators of ALT/WDL were size of lesion and lipomatous content, but due to the overlap in the MRI appearances of lipoma and ALT/WDL, discrimination should be based on molecular pathology rather than imaging.

Primary oral and maxillofacial liposarcoma: a clinicopathological and immunohistochemical study of eleven cases

INTRODUCTION

The present study was aimed to characterize the clinicopathological, immunohistochemical features and treatment outcomes of primary oral and maxillofacial liposarcomas by presenting the experience over a 16-year period at a tertiary referral Chinese institution for head neck cancer.

MATERIAL AND METHODS

This retrospective clinical study included 11 cases of pathologically confirmed primary liposarcomas treated from January 1993 to September 2009. Detailed information regarding primary site, clinical manifestations, histopathological and immunohistochemical analysis, treatments and prognosis was collected and reported.

RESULTS

Eight female and 3 male patients aged from 8 to 76 years old. These lesions occurred in buccal (3), parotid (2), temporal (2), tongue (2), palate (1) and oropharyngeal (1) region. They were histopathologically categorized into 4 subtypes based on WHO classification scheme: atypical lipomatous tumor/well-differentiated (4), myxoid (4), mixed-type (2) and pleomorphic (1) liposarcomas. Immunohistochemical staining indicated mostly positive for Vimentin and S-100 but negative for other markers. Most patients presented as slow-growing painless masses and underwent surgery alone or combined with postoperative radiotherapy. Two patients were misdiagnosed and inappropriate treated and developed local relapse before referred to our institute. No distant metastasis and one disease-related death were recorded during the follow-up (ranging: 1-11 years, mean: 4.5 years).

CONCLUSIONS

Oral and maxillofacial liposarcoma is exceedingly rare and has atypical clinical manifestations but characteristic histopathology. Complete excision with negative margins followed by long-term follow-up is recommended as the treatment of choice for these uncommon entities.

Magnetic resonance imaging of malignant soft tissue neoplasms in the adult

This review addresses the spectrum of malignant soft tissue tumors frequently found in adults. Rather than presenting a complete review, the focus of this discussion is on common lesions or lesions in which the diagnosis may be suggested on the basis of imaging. Diagnoses covered include undifferentiated high-grade pleomorphic sarcoma, fibrosarcoma, dermatofibrosarcoma protuberans, liposarcoma, synovial sarcoma, malignant peripheral nerve sheath tumor, clear cell sarcoma, hemangioendothelioma, hemangiopericytoma, angiosarcoma, and leiomyosarcoma.

Musculoskeletal magnetic resonance imaging suggesting the possibility of liposarcoma: correlation between radiologists' certainty of diagnosis and pathology results

OBJECTIVE

Reliable diagnosis of liposarcoma by magnetic resonance imaging (MRI) is essential for surgical planning. The purpose of this study was to correlate radiologists' certainty of the diagnosis of liposarcoma on musculoskeletal MRI with pathology results.

MATERIALS AND METHODS

Between January 2001 and February 2009, 105 patients who radiologically suggested liposarcoma on their MRI reports were retrospectively reviewed. Among them, pathologically confirmed 64 patients (benign, 42; malignant, 22) were included. Two musculoskeletal radiologists reviewed MR reports and classified these into 3 groups according to the degree of certainty of liposarcoma (CL) by consensus: C1, high; C2, undetermined; and C3, low. Classified data were compared with pathology results.

RESULTS

The number of cases in each group was C1, 32; C2, 12; and C3, 20. Group C1 included 17 liposarcomas (53%), 7 lipomas, 4 other sarcomas, 2 hibernomas, 1 abscess, and 1 epidermal cyst. There were 11 lipomas (92%) and one liposarcoma in C2. In C3, all patients had lipomas. Fifteen (47%) of 32 variable benign or malignant tumors were incorrectly diagnosed as liposarcomas.

CONCLUSION

On the diagnosis of liposarcoma, the radiologists' high degree of CL showed high agreement. However, nonadipose tumors were sometimes misdiagnosed as liposarcomas with a high CL. Therefore, we should consider other soft tissue tumors and benign lipomas for the differential diagnosis of liposarcoma.

Case report: hemosiderotic fibrohistiocytic lipomatous lesion: a clinicopathologic characterization

BACKGROUND

A hemosiderotic fibrohistiocytic lipomatous lesion, also called hemosiderotic fibrolipomatous tumor, is a rare and recently described fibrolipomatous entity. Initially considered the result of a reactive inflammatory process from trauma or vascular disease, newer evidence suggests it may be neoplastic in origin.

CASE REPORT

We report the case of a 56-year-old woman with a painful mass in the dorsal aspect of the foot diagnosed as a hemosiderotic fibrohistiocytic lipomatous lesion.

LITERATURE REVIEW

We reviewed all 31 published cases of hemosiderotic fibrohistiocytic lipomatous lesions looking for common clinical, imaging, and histologic patterns. Hemosiderotic fibrohistiocytic lipomatous lesions occur predominantly in the fifth and sixth decades of life (average age, 49.5 years; range, 0.67-74 years). Females predominate 22 to 9. Thirteen of 28 patients had histories of trauma or vasculopathy. Twenty-six of 31 lesions were in the foot. The MRI signal of a hemosiderotic fibrohistiocytic lipomatous lesion follows fat in all sequences. Stranding or septations also frequently are seen. Histologically, the lesions are composed of three main elements in varying proportions: mature adipocytes, spindle cells, and hemosiderin pigment. Ten of 27 resected lesions recurred. Resection types are not reported in many cases. Four of 15 lesions recurred after marginal/intralesional excision, whereas none of three lesions treated by wide excision recurred.

PURPOSE AND CLINICAL RELEVANCE

The high recurrence rate may be related to the difficulty in determining intraoperatively that a resection is complete, secondary to the lack of anatomic boundaries such as a pseudocapsule. Any attempt at wide resection must weigh the morbidity of this surgery against that of a recurrence after a resection which seemed complete intraoperatively. There have been no reports of metastasis.

Ultrasound features of deep-seated lipomas

Purpose

The objective of this study was to describe the sonographic features of deep-seated lipomas.

Methods

A retrospective review of the sonographic features of 64 deep seated lipomas in 64 patients (43 females, 21 males, mean age 46.5, range 16–77 years) seen over an 8-year period (1998–2006) was undertaken.

Results

Features evaluated were location, size, shape, marginal definition, internal echogenicity, including the presence of intermingled muscle fibres and linear internal echoes, acoustic transmission and vascularity. Confirmation was histological in 37 (58%) cases and by typical magnetic resonance imaging (MRI) appearance in 27 (42%) cases.

Conclusion

The results show that although the features of deep-seated lipoma are more variable than those reported for subcutaneous lipomas, the presence of thin internal echoes in conjunction with other less specific features should enable a correct diagnosis.

Muscle fibers inside a fat tumor: a non-specific imaging finding of benignancy

INTRODUCTION

The differential diagnosis between benign and low-grade well-differentiated malignant lipomatous tumors might be very difficult for both the radiologist and the pathologist, although it has practical consequences. Among the criteria, muscular fibers detected inside the lesion are considered radiologically and histologically as a reliable sign of a benign intramuscular lipoma. New genetic criteria are now available. We report two cases of fat tumors containing muscular fibers both radiologically and histologically, but which are definitely malignant, considering genetic criteria.

MATERIAL AND METHODS

Two cases of soft tissue fat tumors, containing muscular fibers on imaging examinations as well as histologically, had an aggressive behaviour, suggesting malignancy. Genetic criteria were therefore used to confirm the clinical impression.

RESULTS

MDM2 and CDK4 confirmed the malignancy in the two cases.

CONCLUSION

Intra lesional muscular fibers detected on imaging or histological examinations should not be considered as a completely reliable sign of a benign intramuscular lipoma. In case of atypical clinical behaviour, genetic criteria should be used to prove the aggressiveness of the tumor.

MR imaging evaluation of disorders of the chest wall

Chest wall lesions constitute a diverse group of thoracic diseases, including those of soft tissue and osseous origin. MR imaging, with its superior tissue-resolving capability and multiplanar image acquisition, is an important tool for assessing chest wall lesions. In this article, the authors review common and uncommon diseases of the chest wall, with an emphasis on the MR imaging characteristics of these diseases. Among the diseases they discuss are diseases of the soft tissue including lipoma, hibernoma, liposarcoma, hemangioma, and lymphoma. They also examine diseases of the osseous thorax, including benign osseous tumors, fibrous dysplasia, and aneurysmal bone cyst. In addition, they discuss such malignant osseous tumors as osteosarcoma and Ewing's sarcoma.

Fluorine-18-deoxyglucose-positron emission tomography imaging with magnetic resonance and computed tomographic correlation in the evaluation of bone and soft-tissue sarcomas: a pictorial essay

Positron emission tomography (PET) imaging has a growing role as an imaging modality to be used in conjunction with magnetic resonance and computed tomographic imaging in the detection, staging, and management of many sarcomas and carcinomas. Since PET is a relatively new modality and the incidence of sarcomas is low, it has not yet been approved for use in all bone and soft-tissue sarcomas. The purpose of this article is to pictorially evaluate soft-tissue and bone sarcomas, including malignant peripheral nerve sheath tumor, synovial sarcoma, osteosarcoma, liposarcoma, rhabdomyosarcoma, malignant fibrous histiocytoma, fibrosarcoma, and myxofibrosarcoma. This pictorial essay illustrates and describes these tumors in various stages of disease progression vis-à-vis fluorine-18-deoxyglucose-PET imaging with computed tomographic and magnetic resonance correlation. Various stages of disease progression will be discussed including initial diagnosis, treatment response, and metastatic involvement.

Magnetic resonance imaging of lipoma and atypical lipomatous tumour/well-differentiated liposarcoma: observer performance using T1-weighted and fluid-sensitive MRI

The aim of this study was to evaluate observer performance using T1-weighted spin-echo and fluid-sensitive MRI sequences in distinguishing between lipoma and atypical lipomatous tumour/well-differentiated liposarcoma (ALT/WDL). Magnetic resonance images of 51 patients with benign lipoma and ALT/WDL of the musculoskeletal system were reviewed. There were 33 benign lipomas and 18 ALT/WDL. The character of septa and nodularity of the fatty tumours on T1-weighted spin-echo sequences and the presence of high signal on fluid-sensitive sequences were assessed. Two independent observers took part. Observer agreement was measured. The two observers achieved sensitivities of 100 and 94% for T1-weighted images and 100% each for fluid-sensitive sequences. Specificities were 76 and 64% for T1-weighted and 70 and 73% for fluid-sensitive images. Observer agreement was very good (kappa 0.87 for T1-weighted and 0.88 for fluid-sensitive images). In distinguishing lipoma from ALT/WDL, observer performance was comparable using T1-weighted and fluid-sensitive MR sequences. High sensitivity and moderately high specificity were attained.

Imaging characteristics of deep-seated lipomatous tumors: intramuscular lipoma, intermuscular lipoma, and lipoma-like liposarcoma

BACKGROUND

Lipoma-like liposarcomas mimic deep-seated lipomas in regard to imaging as well as histological findings and occasionally cause problems concerning diagnosis and treatment. The differences in the imaging findings among these lesions are not well defined. The purpose of this study was to elucidate the differences among the deep-seated adipocytic neoplasms including intramuscular lipoma, intermuscular lipoma, and lipoma-like liposarcoma.

METHODS

The imaging and clinicopathological findings of 40 intramuscular lipomas, 27 intermuscular lipomas, and 22 lipoma-like liposarcomas were evaluated, and the possibilities in the differential diagnosis were assessed.

RESULTS

Although the most frequent symptom was a palpable mass, swelling was a common symptom of intramuscular lipomas and lipoma-like liposarcomas. Imaging studies revealed dumbbell-shaped appearances among intermuscular lipomas, whereas spherical masses were characteristic of intramuscular lipomas and lipoma-like liposarcomas. Computed tomography and magnetic resonance imaging revealed fatty lesions containing streaky structures in benign lesions, and CT revealed foci of hazy amorphous density, representing spindle cell proliferation, in lipoma-like liposarcoma. Although streaky structures corresponding to entrapped muscle fibers were thick and occasionally interrupted in intramuscular lipomas, the streaky structures corresponding to areolar fibrous tissue were thin and were usually not interrupted in intermuscular lipomas. In lipoma-like well-differentiated liposarcomas, thick streaks represented entrapped muscle fibers, and thin streaks represented fibrous tissue or neoplastic spindle cell proliferation.

CONCLUSIONS

The imaging findings are helpful and often afford almost pathognomonic evidence of these lesions and could help with the selection of appropriate surgery.

MRI appearances of common benign soft-tissue tumours

Benign soft-tissue tumours are many times more common than their malignant counterparts, and magnetic resonance imaging (MRI) is the technique of choice for imaging the lesions. This review illustrates the MRI appearances of the most common benign soft-tissue tumours, based on consecutive referrals to our institution. The imaging signs that are useful for diagnosis are described.

Huge renal lipoma with prominent hypervascular non-adipose elements

A primary renal lipoma is a very rare neoplasm of the kidney and only 20 cases have been reported in the literature. We report a case of a huge retroperitoneal mass that presented as a hypervascular tumour with a prominent fat component, mimicking an angiomyolipoma or a liposarcoma in imaging studies. This finding presented a diagnostic challenge in terms of selecting medical versus surgical intervention. Surgical excision of the lesions was performed and the pathological evaluation revealed a renal lipoma with extrarenal growth.

Subcutaneous fibrolipoma in the back

A 65-year-old man presented with a subcutaneous giant mass in his upper back. The tumor had a massive fatty and non-adipose component that enhanced heterogeneously on contrast-enhanced computed tomography and magnetic resonance imaging. Therefore, the lesion was initially thought to be a liposarcoma or spindle cell lipoma. After surgery, the tumor was histologically diagnosed as a fibrolipoma. Subcutaneous fibrolipoma is a rare neoplasm that is defined as a subtype of lipoma.

The tip of the iceberg: a giant pelvic atypical lipoma presenting as a sciatic hernia

Background

This case report highlights two unusual surgical phenomena: lipoma-like well-differentiated liposarcomas and sciatic hernias. It illustrates the need to be aware that hernias may not always simply contain intra-abdominal viscera.

Case presentation

A 36 year old woman presented with an expanding, yet reducible, right gluteal mass, indicative of a sciatic hernia. However, magnetic resonance imaging demonstrated a large intra- and extra-pelvic fatty mass traversing the greater sciatic foramen. The tumour was surgically removed through an abdomino-perineal approach. Subsequent pathological examination revealed an atypical lipomatous tumour (synonym: lipoma-like well-differentiated liposarcoma). The patient remains free from recurrence two years following her surgery.

Conclusion

The presence of a gluteal mass should always suggest the possibility of a sciatic hernia. However, in this case, the hernia consisted of an atypical lipoma spanning the greater sciatic foramen. Although lipoma-like well-differentiated liposarcomas have only a low potential for recurrence, the variable nature of fatty tumours demands that patients require regular clinical and radiological review.

PET evaluation of fatty tumors in the extremity: possibility of using the standardized uptake value (SUV) to differentiate benign tumors from liposarcoma

OBJECTIVE

The relative utility of various preoperative diagnostic imaging modalities, including PET (utilizing FDG and FMT), CT, and MR imaging, for evaluation of lipoma and liposarcoma, especially well-differentiated liposarcoma, was investigated.

METHODS

Imaging findings in 32 patients with histopathologically documented lipoma, including one with fibrolipoma and one with angiolipoma, and 25 patients with liposarcomas whose subtypes included 10 well-differentiated, 10 myxoid, and 5 other types were reviewed retrospectively. Pre-operative imaging included FDG-PET (n = 44), FMT-PET (n = 21), CT (n = 25), and MR imaging (n = 53).

RESULTS

Statistically significant imaging features of MR images favoring a diagnosis of liposarcoma involved lesions containing less than 75% fat (p < 0.001) as well as the presence of septa (p < 0.001). As compared with well-differentiated liposarcoma, benign lesions were differentiated significantly only by the presence of septa (p < 0.001), which also provided significant differentiation on CT (p < 0.05). The mean SUVs for malignant tumors were significantly higher than those for benign lesions in both FDG- and FMT-PET analyses (p < 0.0001, p = 0.0011, respectively). By using a cut-off value for FDG- and FMT-PET set at 0.81 and 1.0 respectively, which provided the highest accuracy, benign lesions were differentiated significantly from liposarcomas (p < 0.001, and p < 0.02). Furthermore, benign tumors and the three subtypes of liposarcoma were divided significantly into four biological grades by FDG- and FMT-accumulation rates (rho = 0.793, p < 0.0001; and rho = 0.745, p = 0.0009, respectively). A cut-off value of 0.81 for FDG-PET provided significant differentiation between benign lesions and well-differentiated liposarcoma (p < 0.01).

CONCLUSIONS

The presence of septa on MR images differentiated lipomas from liposarcoma, even well-differentiated type. PET analysis, especially FDG-PET, quantitatively provided not only the differentiation but also the metabolic separation among subtypes of liposarcoma. Interpretation of the visual diagnostic modalities requires extensive experience and carries a risk of ignoring a critical portion of malignancy. PET metabolic imaging may be an objective and useful modality for evaluating adipose tissue tumors preoperatively.

From the archives of the AFIP: imaging of musculoskeletal liposarcoma with radiologic-pathologic correlation

Liposarcoma is the second most common type of soft-tissue sarcoma, accounting for 10%-35% of these lesions. The World Health Organization has categorized soft-tissue liposarcomas into five distinct histologic subtypes: well differentiated, dedifferentiated, myxoid, pleomorphic, and mixed type. Well-differentiated liposarcomas frequently demonstrate a diagnostic appearance on computed tomographic (CT) or magnetic resonance (MR) images, with a largely lipomatous mass (>75% of the lesion) and nonlipomatous components in thick septa or focal nodules. The CT or MR imaging finding of a nodular dominant focus (>1 cm in size) of nonlipomatous tissue in a well-differentiated liposarcoma suggests dedifferentiated liposarcoma, and biopsy should be directed at the nonadipose component. The high water content of myxoid liposarcoma seen at pathologic analysis and constituting the majority of the lesion is reflected at sonography, CT, and MR imaging. However, the detection of a small amount of adipose tissue in the septa or as small nodular foci superimposed on the background of myxoid tissue allows prospective diagnosis in 78%-95% of myxoid liposarcomas. Pleomorphic liposarcomas are high-grade sarcomatous lesions and typically appear as heterogeneous soft-tissue masses, although small amounts of fat are seen on MR images in 62%-75% of cases, findings that suggest the diagnosis. Mixed-type liposarcomas have features representing a combination of the other subtypes. Primary liposarcoma of bone is exceedingly rare and usually demonstrates aggressive nonspecific features, although fat may be seen. Understanding and recognition of the spectrum of appearances of the various types of musculoskeletal liposarcoma, which reflect their underlying pathologic characteristics, improves radiologic assessment and is vital for optimal patient management.

From the archives of the AFIP: benign musculoskeletal lipomatous lesions

Benign lipomatous lesions involving soft tissue are common musculoskeletal masses that are classified into nine distinct diagnoses: lipoma, lipomatosis, lipomatosis of nerve, lipoblastoma or lipoblastomatosis, angiolipoma, myolipoma of soft tissue, chondroid lipoma, spindle cell lipoma and pleomorphic lipoma, and hibernoma. Soft-tissue lipoma accounts for almost 50% of all soft-tissue tumors. Radiologic evaluation is diagnostic in up to 71% of cases. These lesions are identical to subcutaneous fat on computed tomographic (CT) and magnetic resonance (MR) images and may contain thin septa. Lipomatosis represents a diffuse overgrowth of mature fat affecting either subcutaneous tissue, muscle or nerve, and imaging is needed to evaluate lesion extent. Lipoblastoma is a tumor of immature fat occurring in young children, and imaging features may reveal a mixture of fat and nonadipose tissue. Angiolipoma, myolipoma, and chondroid lipoma are rare lipomatous lesions that are infrequently imaged. Spindle cell and pleomorphic lipoma appear as a subcutaneous lipomatous mass in the posterior neck or shoulder, with frequent nonadipose components. Hibernoma appears as a lipomatous mass with serpentine vascular elements. Benign lipomatous lesions affecting bone, joint, or tendon sheath include intraosseous lipoma, parosteal lipoma, liposclerosing myxofibrous tumor, discrete lipoma of joint or tendon sheath, and lipoma arborescens. Intraosseous and parosteal lipoma have a pathognomonic CT or MR appearance, with fat in the marrow space or on the bone surface, respectively. Liposclerosing myxofibrous tumor is a rare intermixed histologic lesion commonly located in the medullary canal of the intertrochanteric femur. Benign lipomatous lesions may occur focally in a joint or tendon sheath or with diffuse villonodular proliferation in the synovium (lipoma arborescens) and are diagnosed based on location and identification of fat. Understanding the spectrum of appearances of the various benign musculoskeletal lipomatous lesions improves radiologic assessment and is vital for optimal patient management.

Magnetic resonance imaging of autologous fat grafting

A 30-year-old female patient with isolated facial lipodystrophy underwent two sessions of fat injection. MR signals of injected fat at different injection ages were compared to native fat. Native T1 signal was smaller for transplant fat, probably due to a slightly lower fat content and/or fibrosis or due to higher perfusion. T2 signal of transplants was significantly higher than that of native fat. T1 post-contrast was also higher, and contrast uptake of transplanted fat increased slightly with transplant age, which could be explained by an increasing perfusion. This study demonstrates the differences and MR signal time changes of native and transplanted fat.

Predictive value of gadolinium enhancement in differentiating ALT/WD liposarcomas from benign fatty tumors

OBJECTIVE

To determine the predictive value of gadolinium enhancement on MRI in differentiating atypical lipomatous tumor (ALT)/well-differentiated (WD) liposarcoma from benign fatty tumors.

DESIGN

All histologically proven fatty tumors with preoperative gadolinium-enhanced MRI were reviewed. Only those tumors with predominantly fatty signal were included. Sensitivity, specificity, and positive and negative predictive values for both gadolinium enhancement and biopsy as predictors for the final diagnosis of ALT/WD liposarcoma were calculated.

PATIENTS

From 129 patients evaluated for fatty tumors between 1994 and 2002, the patient population was narrowed to 32 excised fatty tumors with preoperative gadolinium-enhanced MRI.

RESULTS

As a predictor of ALT/WD liposarcoma, the presence of gadolinium enhancement showed 100% sensitivity, 71% specificity, 53% positive predictive value and 100% negative predictive value. Needle or incisional biopsy yielded 57% sensitivity, 100% specificity, 100% positive predictive value and 63% negative predictive value for a diagnosis of ALT/WD liposarcoma.

CONCLUSIONS

Gadolinium enhancement of a homogeneous fatty soft tissue tumor is a sensitive screening tool to determine possible diagnosis of ALT/WD liposarcoma. Biopsy, on the other hand, is specific but insensitive.

Lipomatous tumors of soft tissue: MR appearance with histological correlation

There is a broad spectrum of lipomatous tumors that involve soft tissues including ordinary lipomas, variants of lipomas, heterotopic lipomas, lipomatosis, hibernomas and liposarcomas. The recognition of these tumors is important to avoid diagnostic pitfalls. The MR imaging appearance of the lesion, including location, shape and internal architecture, suggests the diagnosis of lipomatous tumors. The signal intensity on T1-, T2-, fat-suppressed T2-weighted (FS-T2) images or short tau inversion recovery (STIR), T1- and fat-suppressed T1-weighted images after Gd-DTPA administration can be a useful aid in distinguishing between biologically different types of lipomatous tumors. The imaging features are often characteristic and reflect the histological pattern of the tumors. We present an overview of the lipomatous tumors and we correlate MR imaging appearance with histological findings.

Lipomas, lipoma variants, and well-differentiated liposarcomas (atypical lipomas): results of MRI evaluations of 126 consecutive fatty masses

OBJECTIVE

Our objectives were to evaluate the reliability of MRI in distinguishing simple lipomas, lipoma variants, and well-differentiated liposarcomas (atypical lipomas) and to identify various imaging mimics of well-differentiated liposarcoma.

MATERIALS AND METHODS

One hundred twenty-six consecutively imaged grossly fatty masses were retrospectively reviewed. MRI examinations, their prospective interpretations, and their corresponding pathology reports were compared to determine the reliability of MRI in distinguishing simple lipomas, lipoma variants, and well-differentiated liposarcomas.

RESULTS

The success of MRI in identifying well-differentiated liposarcomas among other fatty masses was as follows: sensitivity, 100%; specificity, 83%; accuracy, 84%; positive predictive value, 38%; and negative predictive value, 100%. MRI was 100% specific in the diagnosis of simple lipoma. Sixty-three percent of lesions considered suspicious for well-differentiated liposarcoma were actually simple lipomas (13%) and benign lipoma variants (50%), including chondroid lipoma (13%), osteolipoma (6%), hibernoma (6%), lipoleiomyoma (6%), angiolipoma (6%), and infarcted lipoma (13%).

CONCLUSION

Because of differences in treatment, prognosis, and long-term follow-up, it is important to preoperatively distinguish simple lipomas from well-differentiated liposarcomas. MRI is highly sensitive in the detection of well-differentiated liposarcomas and highly specific in the diagnosis of simple lipomas. However, when an extremity or body wall lesion is considered suspicious for well-differentiated liposarcoma, it is more likely (64%) to represent one of many benign lipoma variants.

Malignant fatty tumors: classification, clinical course, imaging appearance and treatment

Liposarcoma is a relatively common soft tissue malignancy with a wide spectrum of clinical presentations and imaging appearances. Several subtypes are described, ranging from lesions nearly entirely composed of mature adipose tissue, to tumors with very sparse adipose elements. The imaging appearance of these fatty masses is frequently sufficiently characteristic to allow a specific diagnosis, while in other cases, although a specific diagnosis is not achievable, a meaningful limited differential diagnosis can be established. The purpose of this paper is to review the spectrum of malignant fatty tumors, highlighting the current classification system, clinical presentation and behavior, treatment and spectrum of imaging appearances. The imaging review will emphasize CT scanning and MR imaging, and will stress differentiating radiologic features.

Differential diagnosis of benign peripheral lipoma from well-differentiated liposarcoma on MR imaging: is comparison of margins and internal characteristics useful?

OBJECTIVE

Our objective was to evaluate the reliability of MR imaging in distinguishing between benign lipoma and well-differentiated liposarcoma.

MATERIALS AND METHODS

The MR images of 35 pathologically proven benign lipomas in 35 patients and 23 well-differentiated liposarcomas in 17 patients were retrospectively reviewed. T1-, T2-, and fat-suppressed T1-weighted images were obtained after administration of gadopentetate dimeglumine. Margins and internal characteristics revealed on the MR images and the degree of contrast enhancement of septa were evaluated. These MR imaging findings were compared for well-differentiated liposarcomas and benign lipomas.

RESULTS

Completely irregular margins were recognized only in benign lipomas with a pathologic diagnosis of infiltrating lipoma. All tumors without a recognizable nonadipose component were benign lipomas (p < 0.05). As for the well-differentiated liposarcomas, thick septa and nodular or patchy nonadipose components were present more frequently in deep and retroperitoneal lesions than in subcutaneous lesions (p < 0.01). No cases showed only thin septa in the deep lesions of well-differentiated liposarcoma, and all cases showed thick septa or nodular or patchy nonadipose components. The septa in well-differentiated liposarcomas enhanced more strongly than did those in benign lipomas. The septa showed no enhancement relative to muscle in 11 of 19 benign lipomas, whereas the septa showed moderate or marked enhancement in all well-differentiated liposarcomas (p < 0.01).

CONCLUSION

Careful assessment of margins and internal characteristics on MR imaging can be a useful aid in further distinguishing between biologically different benign lipoma and well-differentiated liposarcoma.

[An unusual risk of liposuction: liposuction of a malignant tumor. About 2 patients]

Liposuction is a simple and elegant way to treat fatty excess; it has been even used for the treatment of lipomas and some gynecomasties. The goal of this article is to present 2 patients with an unusual complication of this use: the liposuction of a malignant tumor. The first patient consulted following the liposuction of a "gynecomasty", which was in fact a breast cancer. The second was treated by liposuction for an ankle "lipoma"; it proved to be a liposarcoma. In order to avoid liposuction and dissemination of a malignant tumor, the pre-operative investigations have to search clinical peculiarities evoking the diagnosis: an unilateral "gynecomasty", irregular, hard or painless, in a 50-years-old patient, must incite the surgeon to perform a classical excision, just as a recurrent "lipoma", deeply located, voluminous or quickly extensive, situated on the limbs or in the humeroscapular area. Paraclinic investigations may be indicated; doubtful cases must be right away rejected for liposuction, and treated by a surgical excision with strict safety margins and complete anatomopathologic examination of the lesion. Liposuction has become a very useful technique for the plastic surgeon; however, we must not forget, despite of its many advantages the risk for dissemination of an unknown malignant tumor. Every surgeon must keep it in mind and prefer a surgical removal in atypical cases.

Encapsulated versus nonencapsulated superficial fatty masses: a proposed MR imaging classification

OBJECTIVE

The purpose of this study was to assess the MR imaging appearance of palpable fatty masses and to propose terminology for palpable subcutaneous fatty masses that are nonencapsulated on MR imaging.

MATERIALS AND METHODS

We searched the past 7 years of our institution's radiology database for reports of MR images containing the word "lipoma." Medical records were reviewed to identify patients with palpable masses corresponding to fat. Two radiologists retrospectively reviewed the MR images for the presence of an encapsulated or nonencapsulated fatty mass in the region of the palpable abnormality. Pathologic specimens, when available, were also reviewed.

RESULTS

Between 1995 and 2001, 184 palpable subcutaneous fatty masses were evaluated on MR imaging. Of these, 46% (85/184) were encapsulated lipomas and 54% (99/184) were nonencapsulated fatty masses on MR imaging. Four masses (three encapsulated and one nonencapsulated) were surgically resected and had pathology consistent with lipomas.

CONCLUSION

Many palpable fatty masses do not have definable capsules on MR imaging. We propose that a palpable mass that corresponds to a nonencapsulated prominence of subcutaneous fat on MR imaging should be reported as a nonencapsulated lipoma. More definitive reporting of this relatively common lesion will assure the referring clinician of the benign nature.