On the ultrastructure of hibernoma

Breast hibernoma in a male patient: a rare case report and review of the literature

Hibernomas are uncommon, benign, lipomatous tumours of brown fat. Although hibernomas may arise from any region where brown fat exists, common locations include thigh, shoulder, back and neck. We report a rare finding of a breast hibernoma in a 43-year-old male. The patient was managed surgically with an excision of the breast mass. This report will outline the pathology and clinical findings of breast hibernomas and review of the literature.

Mammary Hibernoma: A Rare Entity

Hibernoma arising in the breast is rare and may present as an asymptomatic mass or may be detected by screening mammography. Four histologic types have been identified: typical, myxoid variant, spindle cell variant, and the lipoma-like variant. The most common "typical variant" is composed of pale to eosinophilic multivacuolated cells with interspersed univacuolar cells. Hibernomas are universally benign and are not known to recur or have an aggressive behavior, even in incompletely excised lesions. Hence, their clinical importance lies in distinguishing them from other benign and malignant breast neoplasms as well as inflammatory conditions that come into the histologic or radiologic differential. This review discusses the clinical features, radiologic and histopathologic characteristics, ancillary studies, suggested pathogenesis, differential diagnosis, and treatment of and prognosis for these uncommon lesions.

Hibernoma larynx with large multinodular goitre: unusual airway challenge

A 56-year-old man presented with a 6-month history of progressively increasing neck swelling, dysphagia and hoarseness of voice. CT scan revealed multi-nodular goitre and also showed a lesion in the supraglottis. It also showed another lesion in the supraglottis. Fine-needle aspiration cytology of thyroid revealed follicular cells. Routine flexible laryngoscopy was performed to evaluate vocal cord function; however, we found a smooth well-defined lesion just above the glottis, obstructing the direct view of the vocal cords, and an endangered airway. A provisional diagnosis of a laryngeal cyst was made. With all necessary precautions intubation was performed with a bougie and a reinforced endotracheal tube was inserted. Total thyroidectomy was performed first. With direct suspension laryngoscopy an attempt was made to deliver the laryngeal lesion, however, the lesion could not be removed. A suprahyoid lateral pharyngotomy was performed to deliver the lesion. Histopathology of the lesion revealed hibernoma.

Rare adipose disorders (RADs) masquerading as obesity

Rare adipose disorders (RADs) including multiple symmetric lipomatosis (MSL), lipedema and Dercum's disease (DD) may be misdiagnosed as obesity. Lifestyle changes, such as reduced caloric intake and increased physical activity are standard care for obesity. Although lifestyle changes and bariatric surgery work effectively for the obesity component of RADs, these treatments do not routinely reduce the abnormal subcutaneous adipose tissue (SAT) of RADs. RAD SAT likely results from the growth of a brown stem cell population with secondary lymphatic dysfunction in MSL, or by primary vascular and lymphatic dysfunction in lipedema and DD. People with RADs do not lose SAT from caloric limitation and increased energy expenditure alone. In order to improve recognition of RADs apart from obesity, the diagnostic criteria, histology and pathophysiology of RADs are presented and contrasted to familial partial lipodystrophies, acquired partial lipodystrophies and obesity with which they may be confused. Treatment recommendations focus on evidence-based data and include lymphatic decongestive therapy, medications and supplements that support loss of RAD SAT. Associated RAD conditions including depression, anxiety and pain will improve as healthcare providers learn to identify and adopt alternative treatment regimens for the abnormal SAT component of RADs. Effective dietary and exercise regimens are needed in RAD populations to improve quality of life and construct advanced treatment regimens for future generations.

Pure hibernoma of the breast: insights about its origins

Hibernomas are rare benign tumors composed of cells reminiscent of brown adipose tissue. In the mammary gland, hibernomas are extraordinary rare, with only 4 cases reported previously. We report the fifth case in a 37-year-old woman who presented with a slowly growing mobile mass in her right breast. A 2.2 cm well-circumscribed lobulated mass was completely removed. The histopathologic analysis showed the full characteristics of the hibernoma. A review of the clinicopathologic features of hibernomas, its relation to brown adipose tissue in humans, and considerations about its histogenesis are made.

Spindle-cell hibernoma: a clinicopathologic comparison of this new variant

Spindle-cell hibernoma is 1 of 4 histologic variants of hibernomas, which are rare lipomatous tumors distinguished from other lipomas by their brown fat component. This article presents a case of a spindle-cell hibernoma that developed in the groin of a 58-year-old man, and is 1 of only 5 known cases of spindle-cell hibernoma published in the scientific literature. Minimal information is available regarding the clinicopathologic characteristics of the 4 hibernoma variants: typical, lipoma-like, myxoid, and spindle-cell. Spindle-cell hibernoma is believed to be the rarest variant, accounting for approximately 2% of hibernomas. The spindle-cell variant predominantly develops in the fourth and fifth decades, with an average age at diagnosis of 42.5 years (range, 28-59 years). It has a male predilection of 4:1. Previously reported only in the posterior neck and scalp, the groin is now added to the sites of spindle-cell hibernoma occurrence. Our patient's tumor demonstrated low-attenuation on computed tomography and contained moderately-attenuating internal septae. Histologically, in addition to the multivacuolated brown fat component common to all hibernomas, spindle-cell hibernoma has a spindle-cell element without vacuolization that is CD34 positive. No prior treatment details are available on this particular variant. Our patient was treated by marginal excision and was disease free through 13 months of follow-up.

A Case of Spontaneous Malignant Hibernoma in a Crl:CD(SD)IGS Rat

A firm, tan, well-circumscribed mass that measured 25 × 30 × 35 mm was observed in the thoracic cavity of a 53-week-old male Crl:CD(SD) IGS rat. Histologically, the mass was encapsulated by fibrous tissue and contained fibrovascular septae. Tumor cells were compactly arranged, and most were oval to polygonal in shape with multivacuolated cytoplasm and a centrally located nucleus. In some parts of the tumor, marked cellular atypia and frequent mitoses were evident. Vacuoles in cytoplasm were positive for oil red O. The tumor cells were characterized ultrastructurally by abundant, round to oval mitochondria with transverse closely-packed cristae. Tumor cells were immunohistochemically positive for uncoupling protein 1 (UCP-1). Several thrombi and hemorrhagic or necrotic foci were also observed within the tumor mass. Vascular invasion of the tumor capsule was observed; however, invasion of surrounding tissues or metastases were not observed. Based on the pathology findings, this case was diagnosed as a malignant hibernoma.

CT and MR characteristics of hibernoma: six cases

PURPOSE

The purpose of this study was to describe the computed tomography (CT) and magnetic resonance (MR) imaging findings of hibernoma.

MATERIALS AND METHODS

We retrospectively evaluated imaging findings of CT and MR examinations of six patients (three men and three woman, aged 27-48 years) with histopathological diagnosis of hibernoma.

RESULTS

On CT examination, the lesions were slightly hyperdense, and on T1- and T2-weighted MR images, they were isointense or slightly hypointense compared to the subcutaneous fat. All of these lesions showed contrast enhancement and one out of the six lesions had internal linear septations.

CONCLUSION

Hibernoma has a wide spectrum of CT and MR imaging findings, which should be considered in differential diagnosis, especially with other lipomatous lesions.

Hibernoma: MRI features in eight consecutive cases

AIM

To describe the preoperative magnetic resonance imaging findings of eight histologically-proven cases of hibernoma.

MATERIALS AND METHODS

The site, size, and signal characteristics of eight consecutive hibernomas were retrospectively assessed on T1-weighted spin-echo and short T1 inversion recovery (STIR)/fat-saturated T2-weighted fast spin echo magnetic resonance images. Four patients also had gadolinium-enhanced fat-saturated T1-weighted spin echo imaging. Patient age and sex, and duration of symptoms were recorded.

RESULTS

Three female and five male patients with an average age 36 years (range 16-53 years) were included. Seven lesions occurred in the thigh, four in the anterior compartment and three in the posterior compartment. One lesion occurred superficial to the scapula. All cases demonstrated common magnetic resonance imaging findings of a well-defined, heterogeneous mass, slightly or clearly hypo-intense to subcutaneous fat on T1-weighted spin-echo images, with prominent thin low signal bands throughout the tumour. The lesions failed to fully suppress on STIR or fat-saturated T2-weighted images. Only one of the four contrast-enhanced studies demonstrated increased vascularity in the tumour.

CONCLUSION

The MRI findings of a lesion that is diffusely slightly hypointense to surrounding subcutaneous fat, should prompt the operator to consider hibernoma in the differential diagnosis.

Characterization of the myxoid variant of hibernoma

Hibernomas are rare benign neoplasms composed of brown adipose tissue. Although they were first mentioned in the literature almost a century ago, relatively few reports have documented their range of pathological features. Multivacuolated fat cells with small, central nuclei are typical features of hibernomas. Based on the nature of the stroma and the appearance of the multivacuolated cells, 4 categories of hibernomas are described: typical, lipoma-like, myxoid, and spindle cell. The myxoid variant is very rare. In this report, we present and characterize the spectrum of morphological features of the myxoid variant of hibernoma by describing the case of a 45-year-old white man who was referred to our hospital for treatment of an ovoid mass in the posterior segment of the right deltoid region. Histopathologic examination of the resected specimen revealed a multilobulated, tan-yellow, variegated tumor with a rubbery consistency that was separated by thick fibrous septa with interspersed collections of foamy histiocytes. The mass was initially diagnosed as schwannoma with degenerative changes, but workup revealed a myxoid variant of hibernoma. This report highlights recent advances that may help confirm the diagnosis and explain the differential diagnosis of this rare tumor. This is one of only a few cases of a myxoid variant of hibernoma reported in the literature.

Hibernoma: a report of 2 unusual cases with a review of the literature

Hibernomas are rare neoplasms composed of brown adipose tissue. The behavior of these neoplasms has been described as uniformly benign in humans. The only recurrence cited in the English literature involved a sarcoma with hibernoma-like features, which was reported in abstract form. We present 2 cases of hibernoma, one that continued to grow following partial excision and another at an unusual site (anterior abdominal wall). Both of these tumors overexpressed p53 protein by immunohistochemistry, which was a novel finding. A review of the literature highlights recent advances that may help confirm the diagnosis and explain the biology of these rare tumors.

Fine-needle aspiration characteristics of hibernoma

BACKGROUND

Hibernoma is a rare, benign lipomatous tumor with features of brown fat. The preoperative diagnosis of hibernoma is difficult at times because its clinical, radiographic, and fine-needle aspiration (FNA) characteristics overlap with those of liposarcoma.

METHODS

The preoperative FNA findings of eight surgically excised hibernomas from seven patients (three men and four women, ages 24-60 years) were reviewed. The cytologic features were compared with the histologic features of the corresponding surgical specimens as well as lipomatous tumors and other lesions that may cause confusion in the differential diagnosis.

RESULTS

The FNA cytologic features of the hibernomas were found to correspond well with their histologic appearance. The FNA findings included small, round, brown fat-like cells with uniform, small cytoplasmic vacuoles and regular, small, round nuclei; delicate branching capillaries; and variable numbers of mature fat cells.

CONCLUSIONS

The FNA cytologic features of hibernoma are characteristic and useful in the preoperative investigation of lipomatous tumors, particularly with regard to excluding a diagnosis of liposarcoma.

Chondroid lipoma: an ultrastructural and immunohistochemical analysis with further observations regarding its differentiation

Chondroid lipoma was recently described as a unique, benign, pseudosarcomatous lipomatous tumor with chondroid features, often simulating liposarcoma and myxoid chondrosarcoma. An extended histochemical and immunohistochemical analysis of 13 cases, including the proliferation markers, proliferating cell nuclear antigen (PCNA) and Ki67, as well as ultrastructural studies of eight cases were performed with the intent of further elucidating its differentiation. Staining with toluidine blue and alcian blue at controlled pHs indicated the presence of chondroitin sulfates within the myxohyaline matrix. Immunohistochemically, all tumors were positive for vimentin and S100 protein. Focal immunoreactivity for cytokeratins was seen in 3 of 13 cases; one of these also had intracytoplasmic tonofilament bundles ultrastructurally. Scattered tumor cells stained for CD68 antigen with KP1 in 6 of 13 cases. None of the tumors stained for epithelial membrane antigen (EMA) or alpha-smooth muscle actin. Collagen IV immunostains showed a network of fibrils encircling individual tumor cells in 10 of 13 cases. Intracytoplasmic staining for laminin was found in 9 of 13 cases. Ultrastructurally there was a spectrum of differentiation, ranging from primitive cells sharing features of prelipoblasts and chondroblasts, to lipoblasts and preadipocytes, to mature adipocytes. A striking ultrastructural feature in 5 of 8 cases was the presence of knob-like protrusions of the cell membrane, which contained granular, amorphous, and fibrillar material that appeared to be extruded into the adjacent matrix. The myxohyaline matrix had ultrastructural features of cartilage. Numerous mitochondria and lysosomes were absent, indicating that chondroid lipoma is neither a hibernomatous lesion nor a lipogranuloma. Ki67 immunoreactivity was typically very low and detected only in the more primitive cell population. The findings in this analysis indicate that chondroid lipoma is a pseudosarcomatous lipogenic neoplasm with a unique cell population possessing predominantly features of embryonal fat and, to a lesser extent, embryonal cartilage.

Extrarenal angiomyolipoma with melanocytic and hibernoma-like features

Angiomyolipoma is a tumor commonly occurring in the kidney, but occasionally found in extrarenal sites. Retroperitoneal angiomyolipoma with unusual features presenting in a 39 year old woman with hypertension is reported in this paper. Tumor fat was inconspicuous, and present largely as hibernoma-like microvesicular lipid. Tumor cells also demonstrated positivity for HMB-45 and S-100 protein, and by electron microscopy showed occasional cytoplasmic striated granules indistinguishable from stage II premelanosomes. However, electron microscopy and immunocytochemistry also confirmed the presence of a substantial myogenous component in the tumor, establishing the diagnosis of angiomyolipoma. The implications of these findings, and the role of immunocytochemistry and electron microscopy in the diagnosis of this tumor are discussed.

Involvement of 10q22 and 11q13 in hibernoma

A hibernoma studied cytogenetically had the karyotype 46,XY,t(9;10;11)(q34;q22;q13),t(17;19) (q21.3;q13). The findings are discussed and compared with those of the previous case described in the literature.

Hibernoma in the parotid region

Hibernoma is a benign tumour, arising from vestigial remnants of brown adipose cells, which have persisted from embryonic life. Although it is a well recognized entity, it is an extremely rare tumour. Recent reports estimate 81 cases in the world literature, only seven being in the neck. To our knowledge, it has never been reported in the parotid region. We report such a case and discuss the historical background of a hibernoma, along with its pathological and clinical behaviour.

A case report of "lipomatous hypertrophy of the cardiac interatrial septum", with a proposal for a new term "lipomatous hamartoma of the cardiac atrial septum"

An autopsy case of "lipomatous hypertrophy of the cardiac interatrial septum" (LHIS) combined with marked stenosis and calcification of the aortic and mitral valves due to fibrous valvular endocarditis, malignant lymphoma, and mucin-producing cancer of the pancreas is reported. LHIS and mucin-producing cancer of the pancreas were incidental findings at autopsy. Microscopically, the LHIS in this case consisted of proliferation of mature fat cells, brown fat cells and cardiac muscle cells. Since these three cell types are normal structural components of the interatrial septum, it was considered that the LHIS was a hamartomatous rather than hypertrophic lesion, of the cardiac atrial septum. Accordingly it was concluded that the term "lipomatous hamartoma of the cardiac atrial septum" was more appropriate for this lesion in the case presented here. As far as we know, this is the first reported case of LHIS in Japan.

Hibernomas of the head and neck

Hibernomas are rare tumors derived from brown adipose tissue, a specialized form of fat tissue found in hibernating and nonhibernating animals. Only a minority of reported hibernomas have occurred in the head and neck region. This report describes two cases of cervical hibernomas, one of which was preoperatively diagnosed by the use of fine-needle aspiration biopsy. The clinical and pathologic characteristics of this neoplasm are reviewed. In general, hibernomas are slow-growing tumors with inconclusive evidence for the existence of a malignant variant. A review of the literature supports the conclusion that excision, sparing vital structures, appears to be curative.

Hibernoma. A case report and discussion of a rare tumor

A case report is presented of a large retroperitoneal hibernoma along with the clinical, radiographic, and pathologic findings. Despite the unusual size and location of this hibernoma, the case illustrates the salient features of these rare tumors of brown fat origin. Pitfalls in preoperative diagnosis are discussed. To date, there has been no convincing evidence of malignant potential of this tumor, and total excision remains the treatment of choice.

Cervical hibernoma. Review of the literature and a new case

Hibernoma is the designation for a rare, benign, soft-tissue tumour composed of cells similar to those of brown adipose tissue. Review of the world literature reveals about 80 cases, but only six hibernomas in the cervical region have previously been reported. A case of cervical hibernoma showing descending behaviour is presented, and the histological, histogenetical, and clinical features of hibernomas are discussed. It is stated that the tumours are adequately treated by local excision, as the neoplasms are histologically and clinically benign, but the extensive vascularity may cause troublesome bleeding in some instances.

Endocrine activity in a large hibernoma

Light, ultrastructural, biochemical and histochemical analyses of a large hibernoma revealed endocrine-like secretory activity. By biochemical and gas chromatographic analyses, cholesterol and steroid hormones were detected. These findings were confirmed by detection of cortisol and testosterone, radioimmune assay, and immunocytochemical testing. Morphologic evidence of endocrine-like secretory activity was provided by both transmission and scanning electron microscopic examination, which, in addition, revealed unusual features that have not previously been described for hibernomas: 1) "endoplasmacrine" lipid granule secretion, 2) rows of pedunculated or detached plasmalemmal granules in perisinusoidal cells, 3) periodic plasmalemmal densities, which were present also along membrane remnants surrounding lipid granules, and 4) highly innervated interstitial veins with eccentric lumens and peculiar thick muscular coats, which resembled structures seen in humans only in the central vein of the adrenal gland.

Hibernoma: distinctive light and electron microscopic features and relationship to brown adipose tissue

Four hibernomas and samples of developing human brown and white adipose tissue were observed. Distinctive features of hibernomas were 1) lobules of closely apposed large polygonal cells and capillaries; 2) three principal cell types (granular eosinophilic, multivacuolated, and univacuolated) varying in prominence from case to case; 3) investment of each tumor cell by basal lamina; 4) an inverse relationship between lipid droplet size and the number of mitochondria per unit of cytoplasm; 5) pleomorphic mitochondria with dense matrixes or large, round mitochondria with transverse lamellar cristae; 6) undulating plasmalemmal invaginations; 7) micropinocytotic vesicles; 8) periodic short plasmalemmal densities; and 9) a conspicuous lack of cytoplasmic membrane systems. The frequent association of micropinocytotic vesicles and undulating plasmalemmal invaginations in proximity to capillaries strongly suggests that the invaginations represent a localized cell membrane adaptation for efficient endocytosis. In human fetal brown adipose tissue, which is first recognizable in fetuses of 21 weeks' gestational age, the most characteristic cell was the polygonal multivacuolated cell. Univacuolated cells were present in brown adipose tissue of older fetuses, and in infants and adults entire lobules containing univacuolated cells coexisted with lobules of multivacuolated cells and granular eosinophilic cells. The ultrastructure of human brown adipose tissue resembled that of hibernomas and was similar to previously described features of this tissue in animals. Developing white adipose tissue differed from brown adipose tissue by its loose plexiform arrangement of capillaries and spindle-shaped cells in less circumscribed lobules and by the absence of polygonal multivacuolated cells. The authors did not identify centripetal lobular maturation in white adipose tissue, but peripheral growth "caps" were a common finding in maturing brown adipose tissue. They consider brown adipose tissue to be a special form of adipose tissue, the variable cytologic composition of which is reflected in the histologic spectrum of hibernomas.

Hibernoma: ultrastructural observations

A light and electron microscopic study of a hibernoma and a brief discussion of the functional role of brown fat are presented. The multivacuolar cells composing brown fat have central round nuclei with prominent nucleoli. The quantity of mitochondria and lipid droplets in the cytoplasm of the cells varies considerably. The electron microscopic findings of hibernoma include multivacuolated and univacuolated cells with varying numbers of lipid vacuoles, lysosomes, lipofuscin granules, pinocytotic vesicles, and possibly prominent subplasmalemmal condensations. Interesting findings in this case include the presence of amorphous diastase resistant perodic acid (PAS) Schiff positive peripheral cytoplasmic masses which are variable in size and shape. These collections also appear extracellularly. The presence of these masses, presumably composed of neutral mucopolysaccharides, has not, to our knowledge, been recorded previously.

Atypical lipoma

In a previous clinico-pathologic and prognostic study of a Swedish national series of liposarcoma the designation atypical lipoma was suggested for a group of well-differentiated non-metastasizing liposarcomas characterized by only moderate nuclear atypia. In the present report, 21 new cases of atypical lipoma are described. The tumors were mainly composed of univacuolated fat cells without cellular or nuclear atypia, but also showed univacuolated fat cells with enlarged, moderately polymorphic, dark nuclei. In two of the tumors a few multivacuolated fat cells with scalloped nuclei were found. Small multinucleated cells with overlapping, peripherally arranged nuclei, reminiscent of so-called floret-like cells as in pleomorphic lipoma, could occasionally be seen. Areas of generally delicate linear or patchy fibrosis with atypical nuclei were a common finding. Two atypical lipomas were studied ultrastructurally. The ultrastructural findings suggest that the nuclear polymorphism is of a neoplastic nature rather than of a regressive changed. Nine atypical lipomas were located intramuscularly, two intermuscularly and ten subcutaneously. Five of the subcutaneous tumors and three of the inter-and intramuscular tumors recurred one or more times. Most of them, particularly the subcutaneous ones, had primarily been diagnosed as ordinary lipomas, but re-examination of the histological sections after one or more recurrence revealed overlooked nuclear atypia. Metastasis or dedifferentiation at recurrence was not seen in any case.

Intraosseous "chordoid" sarcoma, chondroblastic or lipoblastic origin?

An unusual sarcoma with myxoid features that apparently originated within the scapula and has been locally aggressive for 10 years is reported. Clinically and by light microscopy it was considered to be a cartilaginous tumor, possibly chordoid sarcoma. By histochemical techniques and electron microscopy it most closely resembles a tumor of brown fat.

Benign lipoblastomatosis: ultrastructure and histogenesis

Ultrastructural study of a case of benign lipoblastomatosis revealed a cellular spectrum which included undifferentiated mesenchymal cells, stellate myxoid cells, fibroblasts, lipoblasts, lipocytes and many intermediate forms. The uni- and multivacuolated fat cells contained membrane and non-membrane bound cytoplasmic vacuoles, predominatly of saturated lipid. Their cytoplasm also contained simple-structured mitochondria devoid of intramatrical or crystalloid bodies. The fine structure of the cellular components of lipoblastomatosis supports the concept that this is a neoplasm related to fetal white fat rather than to brown fat.

Myxoid liposarcoma. An electronmicroscopic study: biological and histogenetic considerations

Ten myxoid liposarcomas (ML) were studied ultrastructurally in an attempt to determine the histogenesis of this neoplasm and structural associations which might contribute to their relatively benign clinical behavior. The findings were compared with normal and neoplastic adipose tissue. Three cell types were observed, i.e., "primitive" mesenchymal cells, intermediate cell types, and lipoblasts at various stages of development. The principle differences between the lipoblastic elements were the number and the size of intracytoplasmic fat vacuoles, the development of basement membrane-like material, micropinocytotic vesicles along the plasma membrane and the quantity and pleomorphism of mitochondria. The tumor vasculature was complex but consistently demonstrated a multilayered basal lamina. This finding has been described in neoplasms associated with a relatively good prognosis. This study demonstrates that the better differentiated lipoblasts in ML share some features with normal brown fetal fat and hibernoma. It is, thus, suggested that ML may be derived from brown adipose tissue.

The ultrastructure of liposarcoma. A study of 10 cases

An ultrastructural study of 10 liposarcomas is reported. Four of the liposarcomas were wholly or predominantly of well-differentiated, lipoma-like or fibrosing type, 3 of myxoid type, 2 of round cell type and 1 pleomorphic type. The well-differentiated, lipoma-like liposarcomas showed cells with a few, large lipid droplets, few organelles and a peripherally located, fairly large nucleus, The well-differentiated liposarcomas of fibrosing type revealed mostly spindle-shaped, fibroblast-like cells, with abundant rough endoplasmic reticulum and inconspicuous lipid inclusions, surrounded by collagen. One well-differentiated liposarcoma contained an area which was similar to brown adipose tissue and hibernoma. The spindle and stellate shaped cells of the myxoid liposarcomas showed abundant rough endoplasmic reticulum and large smooth-membraned vacuoles filled with moderately dense amorphous material, which appeared to be extruded extracellularly by rupture of the vacuoles. Cytoplasmic lipid droplets were seen in most cells but were much less prominent than in the well-differentiated lipoma-like liposarcomas. Ultrastructurally there were many similarities between the myxoid and round cell liposarcoma, indicating a close relationship between the two types. The pleomorphic liposarcoma revealed cells with one or more large, irregular nuclei, numerous large vacuoles after dissolved lipids, abundant dilated cisternae of rough endoplasmic reticulum and rounded, electron-dense bodies corresponding to PAS-positive hyalin globules seen in the light microscope. The ultrastructural study suggests that the variegated cellular appearance of the different subtypes of liposarcoma reflects the wide cellular spectrum seen during the differentiation of adipose tissue and supports the view that all liposarcomas histogenetically represent a single entity.

Liposarcoma of the neck: a clinicopathologic study of 4 cases

A clinicopathological study of 4 patients with liposarcoma in the neck treated surgically is presented. Three of the liposarcomas were located in the supraclavicular region, two to the right one to the left, and one appeared to the left in the back of the neck. Liposarcoma rarely involves the head and neck region. A survey is given of the few reported liposarcomas in this region. Two of the tumors in the present series were well differentiated, one of which recurred repeatedly. The other two tumors were round-cell and pleomorphic in type, both of which recurred. At the end of follow-up 11 and 9 years, the two patients with well-differentiated liposarcomas were alive. The other two patients had died after 5 and 4 years from intercurrent disease and metastatic spread, respectively. The histopathological basis for the diagnosis, distinguishing features of intramuscular (infiltrating) lipoma, hibernoma and spindle cell lipoma, as well as the treatment, are discussed.