Value of clinical, ultrasonographic and MRI signs as diagnostic differentiators of non-benign lipomatous tumours.

Suspicion of malignant change within a lipoma is a common and increasing workload within the UK Sarcoma multidisciplinary team (MDT) network, and a source of considerable patient anxiety. Currently, there is no lipoma-specific data, with regard to which clinical or radiographic features predict non-benign histology, or calculate an odds-ratio specific to a lipomatous lesion being non-benign. We performed a 9-year, double-blind, unmatched cohort study, comparing post-operative histology outcomes (benign versus non-benign) versus 15 signs across three domains: Clinical (size of tumour, depth, growth noticed by patient, previous lipoma, patient felt pain), Ultrasonographic (size, depth, vascularity, heterogenous features, septae) and MRI (size, depth, vascularity, heterogenous features, septae, complete fat signal suppression). Receiver operating characteristic (ROC) analysis, odds ratios and binary logistic regression analysis was performed double-blind. When each sign is considered independently, (ROC analysis, followed by binary logistic regression) only Ultrasound depth is a significant predictor (p = 0.044) of a histologically non-benign lipoma. Ultrasonographically determined vascularity and septation were not statistically significant predictors. None of the clinical signs were statistically significant (p > 0.05). Of the MRI signs none was statistically significant (p > 0.05). However, heterogeneous MRI features fared better than MRI depth. Ultrasound signs (Pseudo R-Square = 0.105) are more predictive of the post-operation histology outcome than Clinical signs (Pseudo R-Square = 0.082) or MRI tests (Pseudo R-Square = 0.052) Ultrasound and Clinical tests combined (Pseudo R-Square = 0.147) are more predictive of the post-operation histology outcome than MRI tests (Pseudo R-Square = 0.052). This work challenges the traditional perception of "red-flag" signs when applied to lipomatous tumours. We provide accurate data upon which an informed choice can be made, and provides a robust bases for expedited risk/benefit. The importance of an experienced and cohesive MDT network is emphasised.

Spindle cell lipoma, dorsum of hand in a 4 year old child: A rare entity.

Lipogenic tumors are an uncommon entity in children. There are several variants of lipoma, of which spindle cell lipoma is an extremely rare and accounts for only 1.5% of all lipoma diagnosis. Spindle cell lipoma rarely involves distal extremities. We report a 4-year old boy with swelling over dorsum of hand operated for aesthetic purposes. The report also highlights the salient cytological features, which can help differentiate this entity from other closer mimics on aspiration cytology, guiding the surgeon for appropriate management.

Clinicopathologic analysis and subclassification of benign lipomatous lesions of the colon.

Benign lipomatous lesions of the colon are generally asymptomatic. A few histologic subtypes are appreciable, but this is poorly studied. We categorized 404 benign colonic lipomatous lesions as vascular lipoma, fibrolipoma, mucosal lipoma, or lipoma not otherwise specified (NOS). We compared patient age and sex, tumor site and size, symptoms, whether the lesion was flat or pedunculated, and whether an overlying epithelial lesion was present. Symptomatic cases (4%) were larger on average than non-symptomatic ones (mean 3.70 cm vs. 1.30 cm, P < 0.0001). Lipoma NOS was commonly right-sided (P < 0.001) and commonly had an associated epithelial proliferation (P = 0.0004). Vascular lipomas were larger (mean 1.93 cm, P < 0.0001) than other types; they were the most commonly symptomatic, though this was not statistically significant. Mucosal lipomas were smallest on average (mean 0.48 cm) and were not associated with any clinical syndromes. Some colonic lipomas are non-incidental. Vascular lipomas are more often large, while lipomas NOS more often have an associated epithelial proliferation. Colonic lipomas are generally sporadic.

Cutaneous intramuscular lipoma: A new subtype of intramuscular lipoma.

Intramuscular lipoma is an uncommon variant of lipoma that occurs inside muscle tissue. Pathogenesis is thought to be related to neoplastic activity of mesenchymal stem cells, but there still is not an established theory. This entity can be found in almost all areas of the body, mostly within or in connection with skeletal muscle tissue. We have encountered an atypical intramuscular lipoma located in the epidermal layer of the right thigh of an otherwise healthy 35-year-old female. The superficial, protruding skin mass resembled a sebaceous nevus or skin malignancy but was histologically composed of well-defined adipocytes between a mixture of muscle fibers, corresponding with the diagnosis of intramuscular lipoma. Intramuscular lipoma of the skin has never been reported before; thus, the authors suggest the classification "cutaneous" intramuscular lipoma to describe lesions located in the dermal or epidermal layer.

The Enigma of "Traumatic Pseudolipoma" and "Traumatic Herniation of Buccal Fat Pad": A Systematic Review and New Classification System of Post-Traumatic Craniofacial Fatty Masses.

PURPOSE: Intraoral traumatic herniation of the buccal fat pad has been reported using various terms such as traumatic pseudolipoma, traumatic prolapse of buccal fat pad, and traumatic avulsion of buccal fat pad. Because there is no uniformity in nomenclature, this condition needs to be distinguished from other entities such as post-traumatic pseudolipoma and lipoma and pseudoherniation of the buccal fat pad. MATERIALS AND METHODS: A systematic review and thorough search of the literature was planned in online databases such as PubMed, Medline, Scopus, Embase, and Google Scholar. The keywords used were traumatic pseudolipoma, traumatic herniation of buccal fat pad, and traumatic prolapse of buccal fat pad. Of 95 articles initially screened, 45 were included in the study. All pertinent data were extracted by the authors independently. Extracted data were cross-examined for any discrepancy. Summary statistics were not used because the research question did not support pooling of data. RESULTS: Only 24 cases were found to have reported the condition correctly. Terms such as traumatic pseudolipoma were used synonymously and erroneously for this condition. CONCLUSION: Based on the gross inaccuracy in reporting, the authors propose a new comprehensive classification of post-traumatic craniofacial fatty masses.

[Soft tissue tumors : Epidemiology, classification and staging]. / Weichteiltumoren : Epidemiologie, Klassifikation und Stadieneinteilung.

Benign, intermediate and malignant soft tissue tumors can be differentiated histologically. Furthermore, the tumors can be subdivided according to their linear differentiation. In the new World Health Organization (WHO) classification of soft tissue tumors from 2013 changes have been made relating to the allocation of known entities, e. g. undifferentiated sarcomas have been formed into a new subgroup and are no longer assigned to the fibrohistiocytic tumors. The term malignant fibrous histiocytoma has been replaced by the undifferentiated sarcoma. Furthermore, two new subgroups were incorporated, the nerve sheath tumors and gastrointestinal stromal tumors. These were previously included in the tumor classification of other organ systems. These changes in the new classification are related to the rapid increase in knowledge of the genetics and the cell biology of soft tissue tumors. Malignant soft tissue tumors only represent 1% of all malignant tumors in adults. The largest subgroup of soft tissue tumors in adults is the adipocytic tumors. The liposarcoma, which belongs to this subgroup is one of the most common malignant soft tissue tumors in adults. In childhood malignant soft tissue tumors represent 15% of malignant tumors and rhabdomyosarcoma is the most common malignant soft tissue tumor.

An atypical lipomatous tumor mimicking a giant fibrovascular polyp of the hypopharynx: A case report.

RATIONALE: Giant fibrovascular polyps (GFVPs) found in the hypopharynx are exceedingly rare. These are benign tumors which are identified by CT or MRI and usually treated based on symptoms. Even more rarely, pathology may identify one of these masses as an atypical lipomatous tumor (ALT). This paper will present a case of an ALT of the hypopharynx that was originally classified as a GFVP, highlighting the difficulty in distinguishing between them and the importance of making the correct diagnosis. PATIENT CONCERNS: An 84-year-old man presented to the emergency department with a 6-month history of a pedunculated hypopharyngeal growth, dysphagia, and intermittent dyspnea. DIAGNOSES: The mass was characterized as a GFVP by barium swallow and MRI. INTERVENTIONS: The hypopharyngeal mass was resected for obstructive symptoms and to confirm the diagnosis. Final pathology found the mass to be more consistent with an atypical lipomatous tumor (ALT). OUTCOMES: The patient's dysphagia and dyspnea resolved. He was free of recurrence at 22 months postoperative. LESSONS: Both GFVPs and ALTs are very rarely found in the hypopharynx but can be easily misclassified as one another. Imaging is useful to initially characterize the mass, but to definitively differentiate between them, pathological analysis is necessary. Although they are rare, it is important to consider both possibilities on the differential for hypopharyngeal masses. Further, accurate analysis is essential to distinguish between them because their definitive management and follow-up is different.

Lipomatous tumours in adrenal gland: WHO updates and clinical implications.

Adrenal lipomatous tumour is a group of adrenal tumours with a significant component of adipose tissue. According to the current World Health Organization (WHO) classification of tumours of endocrine organs, adrenal myelolipoma is the only entity amongst the group of tumours being described. In the literature, other more recently documented adrenal lipomatous tumours included 24 lipomas, 32 teratomas and 16 angiomyolipomas. Rare fatty tumours of the adrenal gland comprised liposarcoma, hibernoma, adrenocortical tumours with fat component and rare adrenal tumours with fat component. Myelolipoma comprises approximately 3% of primary adrenal tumour. It is noted more commonly in females and in the right adrenal gland. Approximately 40 bilateral myelolipomas were reported. The tumour is most frequently recorded in patients between fifth and seventh decades of life. Adrenal lipomas are often seen in males and in the right adrenal gland. They were commonly noted in patients in the sixth decade of life. The diagnosis could only be possible on examination of the surgically removed specimen. Adrenal teratomas were more common in females and with a bimodal age distribution. Slightly over 60% of the patients with adrenal teratoma are symptomatic. Adrenal angiomyolipomas were often symptomatic, more common in females and in the fifth decades of life. To conclude, adrenal lipomatous tumour is uncommon. They are often benign and non-functional. It is important to recognize the features of this group of lipomatous tumours in the adrenal gland as they are being detected on increasing incidence as a result of the wide-spread use of modern imaging modalities.

New classification of spinal lipomas based on embryonic stage.

OBJECTIVE Spinal lipomas are generally thought to occur as a result of failed primary neurulation. However, some clinical features cannot be explained by this theory. The authors propose a novel classification of spinal lipomas based on embryonic changes seen during primary and secondary neurulation. METHODS A total of 677 patients with occult spinal dysraphism underwent 699 surgeries between August 2002 and May 2015 at the National Center for Child Health and Development and Tokyo Metropolitan Children's Medical Center. This group of patients had 378 spinal lipomas, including 119 conus spinal lipomas, 27 lipomyelomeningoceles, and 232 filum lipomas, which the authors classified into 4 types based on neural tube formation during embryonic development. Type 1 is defined as pure primary neurulation failure; Type 2 ranges from primary to secondary neurulation failure; Type 3 consists of secondary neurulation failure (early phase); and Type 4 is defined as secondary neurulation failure (late phase). The authors also review embryogenesis in secondary neurulation and analyze the clinical utility of the new classification. RESULTS There were 55 Type 1 spinal lipomas, 29 Type 2, 62 Type 3, and 232 Type 4. All filum lipomas fell into the Type 4 spinal lipoma category. Association with anorectal and/or sacral anomalies was seen in none of the Type 1 cases, 15 (52%) of Type 2, 35 (56%) of Type 3, and 31 (13%) of Type 4. Urogenital anomalies were observed in none of the Type 1 or Type 2 cases, 1 (2%) of Type 3, and 28 (12%) of Type 4. Anomaly syndromes were present in none of the Type 1 cases, 6 (21%) of Type 2, 3 (5%) of Type 3, and 16 (7%) of Type 4. Associated anomalies or anomaly syndromes were clearly observed only for Type 2-4 spinal lipomas encompassing failed secondary neurulation. Radical resection was feasible for Type 1 spinal lipomas. CONCLUSIONS Secondary neurulation of the spinal cord gives rise to the conus medullaris and filum terminale, which are often involved in spinal lipomas. Formation of spinal lipomas seems to be a continuous process overlapping primary and secondary neurulation in some cases. Association with other anomalies was higher in Type 2-4 spinal lipomas, which included failed secondary neurulation, than in Type 1 lipomas, with failed primary neurulation. On the other hand, radical resection was indicated for Type 1, but not for Type 2, spinal lipomas. The new classification of spinal lipomas based on embryonic stage has the potential for clinical use and agrees well with both clinical and surgical findings. The classification proposed here is still preliminary. Further studies and verification are necessary to establish its clinical utility.

MDM2/CDK4 gene amplification in large/deep-seated 'lipomas': incidence, predictors and clinical significance.

This study of 140 cases assessed the incidence of MDM2/CDK4 gene amplification in lipomatous neoplasms with histological features of a lipoma but which were of clinical concern due to large size (≥50 mm) and/or deep-seated (subfascial) location. Univariate and multivariate statistical analyses were used to identify clinical, radiological and pathological predictors of gene amplification. Differences in local recurrence rates between amplified and non-amplified cases were assessed using survival analysis. The findings indicate that the incidence of MDM2/CDK4 amplification in this setting is low at 5% (95%CI 1.4-8.6%). Variables associated with amplification on univariate analysis were tumour site (thigh, p = 0.004), size (>100 mm, p = 0.033) and presence of equivocal atypia (p = 0.001). Independent predictors on multivariate analysis were size (OR 3.9, 95%CI 1.4-11.3, p = 0.012) and presence of equivocal atypia (OR 12.5, 95%CI 1.9-80.3, p = 0.008). There was no significant difference in local recurrence rates between amplified and non-amplified cases (p = 0.461) based on a median follow-up time of 31 months. Assessment for MDM2/CDK4 amplification, therefore, should be considered in 'lipomas' which are >100 mm in size, show equivocal atypia and arise in the thigh. However, the clinical significance of gene amplification in this setting is unclear and requires confirmation in larger studies.

Klippel-Trenaunay syndrome belongs to the PIK3CA-related overgrowth spectrum (PROS).

Klippel-Trenaunay syndrome (KTS), originally described as a triad of cutaneous capillary malformation, bone and soft-tissue hypertrophy, as well as venous and lymphatic malformations, has been considered by dermatologists as a distinct diagnostic entity. However, cases with KTS have also been reported to have neurological disorders, developmental delay and digital abnormalities, indicating multisystem involvement. Recently, a number of overgrowth syndromes, with overlapping phenotypic features with KTS, have been identified; these include MCAP and CLOVES syndromes as well as fibroadipose hyperplasia. These conditions harbour mutations in the PIK3CA gene, and they have been included in the PIK3CA-related overgrowth spectrum (PROS). Based on recent demonstrations of PIK3CA mutations also in KTS, it appears that, rather than being a distinct diagnostic entity, KTS belongs to PROS. These observations have potential diagnostic and therapeutic implications for KTS.

Differentiation of lipoma and atypical lipomatous tumor by a scoring system: implication of increased vascularity on pathogenesis of liposarcoma.

BACKGROUND: Well-differentiated liposarcoma (WDL)/atypical lipomatous tumor (ALT) is considered a low-grade malignancy that rarely metastasizes but should be carefully followed because recurrence or dedifferentiation may occur. It is recognized that WDL and ALT are essentially synonymous, describing lesions that are identical both morphologically and karyotypically, and that site-specific variations in behavior relate only to surgical resectability. Preoperative differential diagnosis between lipoma and ALT has been well studied because their clinical and image characteristics are very similar. We evaluated the factors that may differentiate ALTs from lipomas, and validated a tentative scoring system for the diagnosis of the 2 tumor types. METHODS: Forty-eight lipomas and 12 ALTs were included. The mean age, location and depth of the tumor as well as the compartment were not significantly different between the 2 groups. To evaluate the vascularity of the tumors, the average number of intratumoral vessels on pathological sections was calculated and compared between cases of lipoma and ALT. RESULTS: The tumor size was significantly larger in ALT cases than in lipoma cases (P < 0.001). Magnetic resonance imaging (MRI) revealed septal structures in 91.6% of ALTs, whereas 20.8% of lipomas showed septa. Contrast enhancement in MRI was found significantly more often in ALTs (81.2%) than in lipomas (18.8%) (P < 0.001). We created a "ALT score" to discriminate between lipoma and ALT (0-6 points). ALT cases gave significantly higher point values (average 5.1 points) than lipoma cases (average 1.7 points) (P < 0.001). We found a significantly increased number of vessels in cases of ALT than in cases of lipoma (P = 0.001). CONCLUSIONS: Our ALT score may help surgeons to differentiate a suspected ALT from a lipoma and could recommend a marginal resection in cases of suspected ALT. Increased intratumoral vascularity in ALT is reflected in the MRI findings and may play a key role in the acquisition of a malignant phenotype in adipocytic tumors.

Renal leiomyoma: a contemporary multi-institution study of an infrequent and frequently misclassified neoplasm.

Renal leiomyoma is an exceptionally rare benign mesenchymal tumor of the kidney predominantly arising in proximity of the renal capsule or pelvis. Its rarity and nonspecific clinical and imaging features may lead to radical or partial nephrectomy on the basis of preoperative suspicion of renal cell carcinoma. The diagnosis of renal leiomyoma is challenging because of the histologic overlap with lipid-poor angiomyolipoma (AML). We conducted a multi-institution study to characterize renal leiomyoma in greater detail. We collected and reviewed 24 cases diagnosed initially as renal leiomyoma in 10 institutions from North America, Canada, and Europe. Immunohistochemical expression of desmin, HMB-45, estrogen receptor (ER), progesterone receptor (PR), and cathepsin K was evaluated. Upon central review, 9 tumors were classified as renal leiomyoma, whereas the remaining were reclassified as AML (n=13), myolipoma (n=1), and medullary fibroma (n=1). All renal leiomyomas were solitary and occurred in female patients (mean age 63 y; range, 44 to 74 y). Tumor size ranged from 0.6 to 7.0 cm (mean 2.9 cm); 7 originated from the renal capsule or the subcapsular area and 1 from a large vessel in the renal sinus. All leiomyomas were diffusely positive for desmin and negative for HMB-45 and cathepsin K; 6/9 (67%) showed diffuse ER and PR expression, and 1 case showed focal ER positivity only. Renal leiomyoma should be included in the histologic differential diagnosis of solid renal masses, particularly in perimenopausal women. The main differential diagnosis is with lipid-poor AML, and cathepsin K plays a key role in distinguishing these 2 lesions.

[Clinical classification and surgical management of cervicothoracic intraspinal lipomas].

OBJECTIVE: To explore the clinical classification and surgical management of cervicothoracic intraspinal lipomas. METHODS: A total of 22 patients with cervicothoracic intraspinal lipomas were analyzed retrospectively with regards to clinical manifestations, radiographic features, intraoperative findings, surgical techniques and follow-ups. RESULTS: Total (n = 4), subtotal (n = 7) and partial (n = 11) resection was performed. Long-term neurological outcomes were evaluated by modified McCormick classification scheme. Their symptoms improved (n = 15), unchanged (n = 3) and deteriorated (n = 4). And cervicothoracic intraspinal lipomas could be classified into extradural, transitional, chaotic and secondary intramedullary groups. CONCLUSION: Different groups of cervicothoracic intraspinal lipomas vary in the degree of resection and surgical efficacy. Total resection may be performed on most extradural lipomas. The surgical objective of transitional lipomas is decompression. Chaotic and secondary intramedullary lipomas should target effective resection to avoid neurological function injury. Intraoperative use of laser facilitates tumor resection. Intraoperative electrophysiological monitoring protects spinal cord.

Sialolipoma of a minor salivary gland in a dog.

A 10-year-old golden retriever dog was presented for evaluation of progressive panting, inspiratory stridor, and gagging. Oropharyngeal examination revealed a soft, nonulcerated, pedunculated mass arising from the right tonsillar fossa. The mass was completely excised and histopathology was consistent with a sialolipoma. No regrowth of the mass was evident 6 months after surgery.

Lipome salivaire d'une glande salivaire mineure chez un chien. Un chien Golden retriever âgé de 10 ans a été présenté pour l'évaluation d'un halètement progressif, d'un stridor respiratoire et des haut-le-cœur. Un examen oropharyngien a révélé une petite masse molle non ulcérée et pédonculée se dressant sur la fosse de l'amygdale droite. La masse a été entièrement excisée et l'histopathologie était conforme à un lipome salivaire. Six mois après la chirurgie, aucune repousse de la masse n'a été constatée.(Traduit par Isabelle Vallières).

Endobronchial lipomatous tumors: clinicopathologic analysis of 12 cases with molecular cytogenetic evidence supporting classification as "lipoma".

Lipomatous lesions rarely involve the bronchial tree, and detailed morphologic and molecular cytogenetic analysis of these tumors is lacking. The clinicopathologic features of 12 endobronchial lipomatous neoplasms were studied, with ancillary fluorescence in situ hybridization performed in subsets of cases for CPM, which is amplified in atypical lipomatous tumors/well-differentiated liposarcomas (ALT/WDL), and HMGA1 and HMGA2, which are often rearranged in lipomas. The cases occurred predominately in older men (91%) (age range 44 to 80 y, mean 65 y). Most patients (80%) had a former or current history of heavy smoking (20 to 100 pack-years). Three patients had concurrent pulmonary squamous cell carcinoma, and 1 had a history of multiple lung cancers. Most lesions were small (<2.5 cm) and discovered incidentally. A subset of tumors showed atypical morphologic features that would be suggestive of ALT/WDL in soft tissue sites, including regions of fibrosis and scattered hyperchromatic stromal cells. However, all cases with atypia were CPM negative and behaved in a clinically benign manner. Seven cases were tested for HMGA1 and HMGA2 rearrangement; 4 showed HMGA2 rearrangement, and 1 showed HMGA1 rearrangement, consistent with lipomas. Two cases were negative for HMGA1/2 rearrangements. We conclude that endobronchial lipomatous neoplasms represent lipomas, even in the presence of morphologic features suggestive of ALT/WDL. Ancillary fluorescence in situ hybridization testing may be very valuable in the analysis of these rare tumors, as true ALT/WDL seem to be very rare or nonexistent at this anatomic site.

Fibrosarcoma-like lipomatous neoplasm: a reappraisal of so-called spindle cell liposarcoma defining a unique lipomatous tumor unrelated to other liposarcomas.

The term "spindle cell liposarcoma" has been applied to liposarcomas (LPSs) composed predominantly or exclusively of spindled cells. These tumors have been considered variants of well-differentiated LPS (WDL), myxoid LPS, and spindle cell lipoma, suggesting that this is a heterogenous group of lesions. Using strict morphologic criteria and molecular and immunohistochemical analyses, we have identified a homogenous group of spindle cell lipomatous tumors, histologically and genetically distinct from other forms of LPS, which we have called "fibrosarcoma-like lipomatous neoplasm." Cases classified as "spindle cell LPS" or "low-grade LPS with spindle cell features" were reviewed. Final selection criteria included: (1) an exclusive low-grade spindle cell component resembling fibrosarcoma; (2) a mixture of bland fibroblastic cells resembling the preadipocyte and early-adipocyte stage of embryonic fat; and (3) molecular-genetic analysis that excluded other forms of lipomatous tumors. Of the initial 25 cases identified, comparative genomic hybridization (CGH) was uninformative in 2 cases; 5 were reclassified as WDL on the basis of molecular data (MDM2 amplification) and 6 as spindle cell lipoma (CGH profiles with a few gains and losses including a constant loss of chromosome 13 and frequent losses of chromosomes 16 and 6). The 12 remaining cases showed flat CGH profiles; of these cases, 11 were negative for DDIT3 gene rearrangements, and 1 result was uninterpretable. Patients ranged in age from 15 to 82 years (mean 50 y); male patients were affected slightly more often (7:5). Tumors arose in the deep (6) and superficial (3) soft tissue of the groin (4), buttock (3), thigh (2), flank (1), shoulder (1), and paratesticular tissue (1) and ranged in size from 2 to 20 cm (mean 7.5 cm). Clinical follow-up in 11 patients (9 mo to 20 y; mean 68 mo) showed no recurrences or metastases. As defined above, "fibrosarcoma-like lipomatous neoplasm" is a unique lipomatous tumor that should be distinguished from WDL/(low-grade) dedifferentiated LPS and myxoid LPS on combined histologic/molecular features because of its better prognosis.

Hibernoma: comparing imaging appearance with more commonly encountered benign or low-grade lipomatous neoplasms.

OBJECTIVE: Hibernoma is a benign neoplasm comprised of brown fat and characteristic hibernoma cells often occurring in adults with proximal extremity/truncal predilection. Limited reports regarding imaging appearance and clinicopathological features of this rare tumor are available. Four histological subtypes have been described. We present nine patients with hibernoma evaluating preoperative imaging findings (eight MRI; one PET, CT), which may distinguish hibernoma from more common benign or low-grade lipomatous neoplasms and attempt to correlate imaging with histological subtype. Clinicopathological data of 14 patients are presented. MATERIALS AND METHODS: Following IRB approval, retrospective review identified 14 patients from our institution between 2000 and 2012. Preoperative imaging, pathology, and medical records were reviewed. We tested the reader's ability to distinguish hibernoma from lipoma and atypical lipomatous tumor (ALT) at preoperative MRI based on specific imaging criteria. In a separate test, another reader attempted to predict histological subtype. Diagnostic accuracy was recorded. RESULTS: Six men and eight women with a mean age of 53 years were identified. Tumors involved the thigh (4), buttock (3), paraspinal muscles (3), retroperitoneum (2), shoulder (1), and knee (1). Eleven underwent margin negative resection; three excisional biopsy. When asked to differentiate hibernoma from lipoma and ALT, readers correctly identified 80 %, 80 %, and 100 % of hibernomas. Specific histological subtype was accurately predicted in most cases. Mean follow-up was 38 months with no local recurrences or metastases. CONCLUSIONS: Hibernomas can be difficult to differentiate from other lipomatous neoplasms, but identification of certain imaging features, common location, and patient demographics can improve preoperative confidence. Given benignity, accurate prospective diagnosis may affect treatment planning and surveillance strategy.

A mammary gland chondrolipoma in the dog.

A 12-year-old intact female dog was submitted to surgery to remove a well-circumscribed mass located near the left inguinal mammary gland. At histological examination, the mass was unencapsulated and composed by lobules of fat cells and scattered isles of cartilaginous tissue. Chondroblasts and chondrocytes showed moderate signs of atypia and often were located singularly or in small clusters within the stroma of the neoplasm. Immunohistochemical analysis revealed that cells were vimentin and S-100 positive, whereas no immunoreactivity was showed for cytokeratin, cytokeratin 5/6, cytokeratin 14, and P63. A diagnosis of chondrolipoma was made based on microscopic findings.