Membranous fat necrosis

A Rare Case of Extraosseous Ewing's Sarcoma/Primitive Neuroectodermal Tumor in Female

Extraosseous Ewing's sarcoma (EES) is a rare form of Ewing's sarcoma that arises outside the bones in soft-tissue structures. It is thought to result from a genetic abnormality involving the fusion of the EWSR1 gene with various partner genes, most commonly the FLI-1 gene. Common symptoms include pain, swelling, and sometimes a palpable mass at the site of the tumor. Diagnosis typically involves imaging studies such as magnetic resonance imaging (MRI), computed tomography (CT) scans, and biopsy for confirmation. Treatment typically includes a combination of chemotherapy, surgery to remove the tumor, and sometimes radiation therapy. In this report, we present a case of EES in a 44-year-old female who presented with complaints of swelling in the right thigh for 3 months. The mass was soft in consistency with well-delineated borders, evident both clinically and radiologically, extending into the subcutaneous layer and involving the right inguinal lymph nodes. The mass was widely excised with en-bloc dissection of the right inguinal nodes. The histopathological features confirmed the diagnosis and have been discussed in this study. This case underscores the clinical significance of EES, a rare variant presenting diagnostic challenges. Our findings highlight the importance of prompt diagnosis and early management to improve outcomes for patients with this aggressive malignancy.

Lipomembranous fat necrosis: A distinctive and unique morphology (Review)

Lipomembranous fat necrosis (LFN) is an uncommon but distinct form of fat necrosis, which is characterized by eosinophilic, crenulated and/or serpiginous membranes. LFN exhibits macrocystic, microcystic and/or crushed features. LFN is routinely detectable on hematoxylin and eosin (H&E)-stained sections, and is present both in the acute phase and in the later or fibrous stage of necrotic fatty lesions. Smaller crushed LFN embedded within fibrous tissues may be difficult to recognize on H&E-stained sections, but can be highlighted by some staining techniques, including Masson trichrome, periodic acid-Schiff, orcein, long Ziehl-Neelsen stain, silver impregnation, phosphotungstic acid-hematoxylin and luxol fast blue staining. LFN was initially considered a specific feature of Nasu-Hakola disease, but has since been identified in various subcutaneous or intraabdominal lesions related to ischemic conditions or venous insufficiency. In addition, LFN is detectable in intra-articular loose bodies and aortic valves with or without dysfunction, suggesting that LFN is also associated with ischemia-like hypoxic conditions or malnutrition. LFN is considered to be a histological hallmark of hidden ischemic or hypoxic/malnourished conditions in various diseases; however, the exact mechanisms of LFN remain poorly understood. The present review described the clinicopathological features of this interesting, but poorly characterized, condition.

Pseudomembranous changes in the dermis: A novel observation and potential clue for evolving lipodermatosclerosis?

Lipodermatosclerosis (LDS) is a well-recognized form of fibrosing panniculitis. Although chronic cases are readily diagnosed, early and evolving lesions may be clinically mistaken for cellulitis and other forms of panniculitis. Most pathologists are familiar with a pseudomembranous type of fat necrosis as a useful feature of chronic LDS. Although nonspecific, this distinctive pattern of fat necrosis helps in supporting a diagnosis of LDS in the appropriate clinical context. The histopathologic features of early and evolving LDS and those involving the dermis are less well documented. We report a case of early LDS showing extensive pseudomembranous changes in the dermis on a superficial skin biopsy where progression to a classic established lesion was documented clinically. We suspect that this previously unreported and unusual finding may be a histopathologic clue for evolving lesions of LDS.

Perspectives in Pediatric Pathology, Chapter 19. Testicular Torsion, Testicular Appendix Torsion, and Other Forms of Testicular Infarction

Among the most frequent specimens at the pediatric surgical pathology bench, orchiectomy performed after testicular torsion deserves significant attention. Multiple implications, including fertility, legal complications, possibility of occult lesion, and others, need to be considered. Furthermore, torsion of testicular and other appendices represents common urological emergencies frequently encountered in surgical pathology. Here we present a review of testicular torsion and infarction, including theories about their pathogenesis and the appropriate handling by the diagnostic pathologist.

Benign soft tissue lesions that may mimic malignancy

Soft tissue lesions which mimic malignancy (pseudosarcomas), represent a significant diagnostic challenge for pathologists. Many features often associated with malignancy including rapid and infiltrative growth, increased cellularity and mitotic activity, and nuclear pleomorphism are present in benign and reactive conditions. This review highlights repair reactions including nodular fasciitis, proliferative fasciitis/myositis, intravascular papillary endothelial hyperplasia, and fat necrosis; lipoma and spindle cell/pleomorphic lipoma; fibroepithelial stromal (pseudosarcomatoid) polyp; phosphaturic mesenchymal tumor; and myxoma. While not inclusive of every pseudoneoplastic soft tissue lesion, this review emphasizes important diagnostic pitfalls and stresses the value of clinical, pathologic, and radiologic correlation.

Fat Necrosis of the Breast: A Pictorial Review of the Mammographic, Ultrasound, CT, and MRI Findings with Histopathologic Correlation

Fat necrosis of the breast is a challenging diagnosis due to the various appearances on mammography, ultrasound, CT, PET-CT, and MRI. Although mammography is more specific, ultrasound is a very important tool in making the diagnosis of fat necrosis. MRI has a wide spectrum of findings for fat necrosis and the appearance is the result of the amount of the inflammatory reaction, the amount of liquefied fat, and the degree of fibrosis. While CT and PET-CT are not first line imaging examinations for the diagnosis of breast cancer or fat necrosis, they are frequently performed in the surveillance and staging of disease. Knowledge of how fat necrosis presents on these additional imaging techniques is important to prevent misinterpretation of the imaging findings. Gross and microscopic appearances of fat necrosis depend on the age of the lesion; the histologic examination of fat necrosis is usually straightforward. Knowledge of the variable appearances of fat necrosis on a vast array of imaging modalities will enhance a radiologist's accuracy in the analysis and interpretation of fat necrosis versus other diagnoses.

Fatty lesions in intra-articular loose bodies: a histopathological study of non-primary synovial chondromatosis cases

Intra-articular loose bodies (ILBs) are not uncommon conditions in patients with various joint diseases. Their morphological alterations have been investigated in detail, but little attention has been paid to their fatty lesions. In this study, we examined fatty bone marrow, fat cells without bone marrow structures (extramedullary fat cells), and their necrotic changes in 55 ILBs surgically removed from 42 patients, excluding primary synovial chondromatosis cases. The presence of viable re-vascularized vessels with or without enchondral ossification could discriminate 19 re-attached ILBs from 36 true free ILBs. Fatty bone marrow was found in 25 ILBs, and its necrosis was recognized in 11 (44.0%) of them. Extramedullary fat cells, characterized by single or clustered fat cells focally or multifocally distributed in fibrous or cartilaginous stroma, were identified in seven true free ILBs (7of 55, 12.7%), and all of them were focally necrotic. Unique lipomembranous changes were detected in 7 (12.7%) of 55 ILBs; they were found in 4 (36.4%) of 11 ILBs of necrotic bone marrow and were associated with 3 (42.9%) of 7 necrotic extramedullary fatty lesions. These changes were highlighted by periodic-acid Schiff and Masson's trichrome stain more clearly. We concluded that extramedullary fat cells represent lipometaplasia in ILBs with no blood supply. We considered that lipomembranous changes in ILBs can be a useful hallmark for necrotic bone marrow or necrosis of extramedullary lipometaplastic lesions.

A case of membranous lipodystrophy observed in lichen amyloidosis

Membranous lipodystrophy is characterized by the presence of microcysts lined by amorphous, eosinophilic material with an arabesque appearance. We experienced a case of a 72-year-old man who had dark brownish, pruritic papules on the arms, legs, and back. Histopathologic examination of a biopsied lesion showed homogeneous, eosinophilic material in the papillary dermis, as well as membranous lipodystrophy. We report a case of membranous lipodystrophy observed in lichen amyloidosis.

Membranous lipodystrophy-like changes in two cases of traumatic lipogranuloma caused by safety belts

A few cases of subcutaneous nodules with the histological findings of membranous lipodystrophy-like changes have been reported in the literature. However, reports of membranous lipodystrophy-like changes caused by trauma are exceedingly rare. We report two cases of traumatic lipogranuloma that had linear and multiple lesions showing membranous lipodystrophy-like changes and were induced by safety belt trauma after a car accident. These patients showed peculiar changes in their subcutaneous fat and had linear patterned, multiple, nodular lesions with membranous lipodystrophy-like changes caused by trauma.

Pseudotumoral encapsulated fat necrosis with diffuse pseudomembranous degeneration

An extraordinary case of encapsulated fat necrosis characterized by its large size, diffuse formation of pseudomembranes, and tendency to recur after excision is reported. A 67-year-old Caucasian woman suffering from morbid obesity was admitted for diagnosis and surgical treatment of a soft tissue mass showing a longest diameter of 14 cm and lying adjacently to the scar from previous appendicectomy. Histopathologic features were consistent with a nodular-cystic encapsulated fat necrosis with diffuse pseudomembranous transformation. Eight months after surgery, a new larger mass (longest diameter of 18 cm) sharing identical histopathologic features appeared in the same location. Encapsulated fat necrosis is a well-defined entity even though several names have been proposed for this condition, including mobile encapsulated lipoma, encapsulated necrosis, or nodular-cystic fat necrosis. Its pathogenesis seems to be related to ischemic changes secondary to previous trauma. It may occasionally show degenerative changes, including dystrophic calcifications and presence of pseudomembranes. To our knowledge, these are the first reported cases of encapsulated fat necrosis presenting as lesions of such size and showing diffuse formation of pseudomembranes; these particular features made diagnosis difficult and led to consideration of a wide range of potential diagnostic possibilities. This case expands the clinico-pathologic spectrum of membranocystic fat necrosis, including the potential ability of this subcutaneous fatty tissue abnormality to recur after surgical excision. Felipo F, Vaquero M, del Agua C. Pseudotumoral encapsulated fat necrosis with diffuse pseudomembranous degeneration.

Membranous Fat Necrosis of the Breast: Diagnosis by Minimally Invasive Technique

Clinical and mammographic features of membranous fat necrosis (MFN) may simulate breast malignancy and tissue sampling is essential for accurate diagnosis. The aim of our study was to evaluate the clinical and imaging findings in these patients. Retrospective review of the records of breast biopsies (n = 1200) during the 5-year period 1998 to 2002 revealed eight (0.67%) cases of histologically proven MFN. Seven of the eight patients had a history of breast trauma or surgery. Seven patients underwent mammography: normal in two, a mass with curvilinear calcifications in one, and heterogeneous calcifications in four. Four patients underwent surgical excision of a palpable mass, one patient had complete excision of calcifications with large core biopsy technique, and three patients had stereotactic vacuum-assisted mammotome biopsy (VAMB). MFN should be included in the differential diagnosis of lesions in a breast with previous trauma or surgery. A minimally invasive diagnostic procedure should be considered in order to avoid excessive excisional surgery.

Subcutaneous pseudomembranous fat necrosis: new observations

BACKGROUND

Pseudomembranous fat necrosis is a peculiar manifestation of necrosis of adipose tissue characterized by formation of pseudocystic cavities lined by crenulated membranes. The underlying mechanism for the formation of pseudomembranes is unknown and numerous hypotheses have been proposed. Despite divergent interpretations, most authors consider necrotic fat cells to be the anatomic substrate for the formation of pseudomembranes.

METHODS

A total of 341 panniculitides were reviewed for the presence of pseudomembranous fat necrosis. The specific diagnoses were established after correlation of all available clinical and laboratory data with the histopathology. Special attention was given to the time in the evolution of the disease when the biopsy was taken. Additional immunohistochemical studies were performed in 12 cases.

RESULTS

Thirty of 341 cases of different types of panniculitides were found to show pseudomembranous fat necrosis, namely: 10 of 15 cases of sclerosing panniculitis (lipodermatosclerosis), 6 of 95 cases of erythema nodosum, 7 of 34 cases of traumatic panniculitis, 1 of 7 cases of lupus panniculitis, 1 of 20 cases of erythema induratum Bazin (nodular vasculitis), 1 of 9 cases of necrobiosis lipoidica, 1 of 4 cases of sclerotic lipogranuloma, 1 of 9 cases of infectious panniculitis (erysipelas), 1 of 2 cases of pancreatic panniculitis, and 1 of 4 cases of subcutaneous sarcoidosis. Pseudomembranous fat necrosis labelled strongly for the histiocytic markers CD68 and lysozyme.

CONCLUSIONS

Our series provides data suggesting that pseudomembranous fat necrosis represents a dynamic process that varies according to the evolution of the lesion at the time of the biopsy. In biopsies taken from early foci of panniculitides pseudomembranes show vescicular or picnotic nuclei. Later, pseudomembranes retain their crenulated appearance but lack nuclear elements. Furthermore, we present histopathologic, histochemical, and immunohistochemical evidence that pseudomembranous fat necrosis results from the interaction of residual products of disintegrated fat cells and macrophages. Histiocytic markers such as CD68 and lysozyme may be used as reliable tools in order to detect pseudomembranes in panniculitides.

Lipomembranous fat necrosis in three cases of testicular torsion

AIMS

To describe for the first time a lesion termed lipomembranous fat necrosis (LFN) in three patients with spermatic cord torsion.

METHODS AND RESULTS

We reviewed 386 testes and their epididymides and spermatic cords which had been removed for testicular infarction. For the three cases showing LFN, a battery of histochemical tests (including periodic acid-Schiff (PAS), orcein, Sudan black and Perls stains) was applied and clinical histories and laboratory data were also investigated. Findings were similar in the three specimens. The testes showed a central group of necrotic seminiferous tubules which were surrounded by granulation tissue consisting of macrophages, multinucleated giant cells, lymphocytes, plasma cells and fibrous connective tissue at the periphery of the lesion. The spermatic cord showed thrombosed veins surrounded by fat necrosis showing cystic cavities which were bounded by wavy hyaline membranes. These stained with Sudan black, PAS (before and after diastase digestion) and orcein and presented yellowish-green autofluorescence.

CONCLUSIONS

Lipomembranous fat necrosis of the spermatic cord is a distinctive entity which seems to be related to spermatic cord torsion and the differential diagnosis of which should be established with regard to the presence of parasites, sclerosing lipogranuloma and granuloma evoked by rupture of a testicular prosthesis.

Vasculitis-induced membranous fat necrosis

Membranous fat necrosis (MFN) a distinct degenerative process of adipose tissue, is characterised by the presence of membranocystic lesions (MCLs) superimposed on a background of typical traumatic-type fat necrosis. MCLs are cysts, of varying size and shape, that are lined by an eosinophilic, crenulated membrane, having the staining properties of ceroid. Although MFN has been documented in varying systemic adipose tissue sites and in tumours, the pathogenesis of this pathological curiosity is unknown. To date, an ischemic basis for MFN has been the most proximate, and atherosclerosis and venous insufficiency, due to large and medium vessel disease, have been the most popular underlying clinical disorders. Although systemic vasculitis has been quoted as the underlying ischemic disorder in some patients, vasculitis has not been commented on nor demonstrated in tissue sections in association with MFN. In,reporting vasculitis-induced MFN, we document the occurrence of MFN in association with uncommon causes of vasculitis, namely: 1) Granulomatous vasculitis in a post-herpetic zosteriform scar; 2) Cytomegalovirus-induced vasculitis in the clinical setting of systemic lupus erythematosus; and 3) Lymphocytic vasculitis in a tetanus toxoid immunization site reaction.

Membranocystic lesion in lumbar yellow ligament

STUDY DESIGN

An examination of surgical cases of membranocystic lesions in the lumbar yellow ligament between the fourth and fifth lumbar vertebrae.

OBJECTIVES

To report the incidence and pathogenesis of membranocystic lesions of the yellow ligament in surgical specimens.

SUMMARY OF BACKGROUND DATA

The membranocystic lesion has been observed not only in membranous lipodystrophy, but also in other conditions. However, there has been no report concerning this lesion in the yellow ligament.

METHODS

Forty-four yellow ligaments excised in surgery were histologically reviewed. In eight cases, S-100 expression was investigated. In two cases, ultrastructural findings were examined.

RESULTS

Membranocystic lesions were present in 8 (18%) of the 44 cases. The cases with the lesions had undergone surgery for spondylolisthesis (4 cases), sequestration-type disc herniation (2 cases), postradiation status (1 case), and spinal stenosis (1 case). Histologically, in all 8 cases, fibrosis was present around the lesion. In 5 of the 8 cases, chondrocytes were observed adjacent to the lesion, and nuclei positive for S-100 protein were observed in 4 cases. Nuclei of chondrocytes adjacent to the lesion also were positive for S-100 protein. Ultrastructurally, irregularly shaped cystic spaces surrounded by an electron-dense membranous structure, which were identical to those of membranous lipodystrophy, were observed.

CONCLUSIONS

These results suggest that degeneration of the chondrocytes has a causal relationship to the formation of membranocystic lesions in the yellow ligament.

Magnetic resonance imaging techniques demonstrate soft tissue damage in the diabetic foot

AIMS

Our objective was to assess the qualitative soft tissue changes which occur in the diabetic neuropathic foot, which may predispose to ulceration, using a specific magnetic resonance imaging (MRI) contrast sequence, magnetization transfer (MT) which produces contrast based on exchange between water bound to macromolecules (e.g. collagen) and free water (e.g. extracellular fluid).

METHODS

The first metatarsal head of 19 diabetic neuropathic subjects and 11 diabetic non-neuropathic controls was studied using a 'targeted' radiofrequency coil. Neuropathy was classified using vibration perception threshold (VPT) (< or > 25 V), cold threshold (< 1 degree C or > 4 degrees C) and Michigan neuropathy score (< 5 or > 15). Peripheral vascular disease was excluded. Results were expressed as percentage of tissue MT activity in a cross-sectional area. At autopsy full thickness biopsies were taken from the plantar fat pad of 10 unrelated subjects with diabetic neuropathy.

RESULTS

Healthy muscle displays high MT activity, whereas adipose tissue induces little activity. Muscle MT activity was considerably reduced (75+/-20%, 30+/-24%, P<0.001) and fat pad MT activity was considerably increased in subjects with neuropathy (37+/-17% 68+/-21%, P<0.001). Muscle fibre atrophy decreases MT activity, whereas fibrous infiltration of the fat pad increases MT activity, fibro-atrophic post-mortem histological changes were found in the plantar fat pads of all neuropathic subjects examined (n = 10).

CONCLUSIONS

Changes in MT activity reflect qualitative structural changes which this study reveals are extensive in the diabetic neuropathic foot. Fibrotic atrophy of the plantar fat pad may affect its ability to dissipate the increased weight-bearing forces associated with diabetic neuropathy.

Cartilaginous membranocystic lesions mimicking membranous lipodystrophy of bone

Two cases are presented in which membranocystic lesions were observed in the cartilaginous tissue of surgical specimens. In both cases, the histological and ultrastructural features were reviewed, and S-100 protein distribution was examined immunohistochemically in one case. In both cases, the membranocystic lesions were observed to be adjacent to ballooned chondrocytes. In one case, several chondrocytes showed partially membranocystic lesions in their cytoplasm. The chondrocytes and nuclei in membranocystic lesions were stained positively for S-100 protein. It is suggested that the membranocystic lesions in the cartilaginous tissue were associated with the degeneration of the chondrocytes.

Membranous fat necrosis in lipomas

Membranous fat necrosis (MFN) is an under-recognized variant of fat necrosis (FN) that is characterized by the presence of membranocystic foci in which cysts are lined by an eosinophilic, homogeneous membrane with pseudo-papillary luminal projections. Although MFN has been described in systemic adipose tissue, it has not been described in lipomas. We report the rare occurrence of MFN in four lipomas. The lipomas ranged in size between 9 and 22 cm and occurred in menopausal women in the left shoulder, right upper back, right thigh, and gluteal regions. In two cases the membranocystic foci were identified macroscopically, whereas in the other two cases MFN was only identified on histologic assessment. Apart from the typical histologic appearance of the membranocystic foci, the membranes have a distinct histochemical profile that includes consistent Sudan black positivity and either periodic acid-Schiff or Ziehl-Neelsen positivity. In all cases, there was autofluorescence of the membranes on immunofluorescent examination of unstained sections. These membranocystic foci have the typical staining reactions of ceroid pigment. The exact cause of MFN in lipomas is not known, but in view of their large sizes, traumatic and ischemic etiologies are proposed.

A clinical and histopathological study of 22 patients with membranous lipodystrophy

Membranous lipodystrophy, an uncommon disorder, was described by Nasu et al. in 1973 as a form of regressive degeneration or localized destruction of the adipose tissue. Clinical features of the lesions with membranous fat necrosis are variable and the condition can only be diagnosed histopathologically. These peculiar changes in fat tissue have been associated with many local and systemic diseases including lupus erythematosus, diabetes mellitus, erythema nodosum, stasis dermatitis, morphoea and trauma, but occasionally no underlying disease is found. Even though various hypotheses concerning the pathogenesis of membranous lipodystrophy have been proposed, the exact causes are still in dispute. We reviewed 22 patients having membranous lipodystrophy confirmed by biopsy and discuss the pathogenetic mechanisms which have been suggested by many authors.

Lipomembranous changes in nodular-cystic fat necrosis

Three cases of nodular-cystic fat necrosis presenting with focal lipomembranous changes are reported. The lesions consisted of solitary (cases 1 and 3) or multiple (case 2) subcutaneous nodules on the upper (case 1) or lower (cases 2 and 3) extremities which had evolved over weeks to years. At surgical excision, solitary or multiple, freely mobile nodules within a cystic cavity were observed. Histologically, encapsulated fat nodules showing variable amounts of necrosis without marked inflammatory changes were present. Focal lipomembranous changes were observed in some nodules. Our observations seem to support the concept that lipomembranous changes are nonspecific and uncommon patterns of fat necrosis caused by a wide variety of local or systemic events that may cause a compromise in the blood supply of the subcutaneous tissue.

Membranous lipodystrophy: secondary type

BACKGROUND

A peculiar type of fat necrosis was noted in some patients with various skin diseases.

OBJECTIVE

We attempted to develop a classification of membranous lipodystrophy combining the results of our study and a review of other articles.

METHODS

Five cases of skin diseases with membranous lipodystrophy were studied and their clinical and histopathologic features were analyzed. Previous reports of similar findings were reviewed.

RESULTS

Membranous lipodystrophic changes were noted in morphea profunda, lupus panniculitis, and factitial ulcer. Microcysts were formed by the coalescence of the destroyed fat cells and were lined by amorphous, eosinophilic material. Some of the linings had a crenelated appearance. Microgranules were found in the histiocytes and in the hyalinized collagen stroma. The linings and microgranules stained positively with periodic acid-Schiff, were resistant to diastase, and also stained with Sudan black B.

CONCLUSION

We propose the use of the term secondary membranous lipodystrophy to describe the local subcutaneous membranous lipodystrophic change that occurs as a result of other skin diseases, in contrast to primary idiopathic membranous lipodystrophy, which occurs without any antecedent factors.

Lipomembranous (membranocystic) changes associated with morphea: a clinicopathologic review of three cases

Lipomembranous (membranocystic) changes represent a distinctive form of pathology in adipose tissue. Although first described in the rare neurodegenerative disorder now called Nasu-Hakola disease, this change has also been observed in a variety of relatively common inflammatory and noninflammatory dermatoses. We report three cases of morphea associated with marked lipomembranous (membranocystic) changes in the subcutaneous adipose tissue.

Granulomatous lipophagic panniculitis and temporal arteritis in a patient with cryptogenic chronic active hepatitis

An elderly woman receiving long term treatment with prednisone and azathioprine for cryptogenic chronic active hepatitis developed granulomatous lipophagic panniculitis and temporal arteritis. The lymphoplasmahistiocytic inflammatory reaction pattern is common to this patient's three diseases. It is suggested that an aberration of the defence mechanisms, immunological or otherwise, is responsible for this unusual occurrence. The triple association of chronic active hepatitis, granulomatous panniculitis and temporal arteritis has not been reported previously.

Membranous lipodystrophy: primary idiopathic type

A 20-year-old woman had a pea-sized, tender subcutaneous nodule on the leg. Histopathologically, the panniculus showed multiple microcysts lined by membranes and light brown granules in the histiocytes. Histochemical studies of the membranes of the microcysts and the granules in the histiocytes indicated that they were composed of ceroid. Electron microscopy revealed that the membrane of the microcyst was composed of electron-dense areas of a regular 18.6 nm lamellar array and reticulated vacuolated areas suggestive of degenerating fat cells of unknown origin. Membranous lipodystrophy has been associated with many local and systemic diseases, but it may be idiopathic, as in our patient.

A light and electron microscopical study of membranocystic lesions in a case of lupus erythematosus profundus

A light and electron microscopical study on membranocystic lesions (MCL) in a case of lupus erythematosus profundus (LEP) is reported. The patient was a 16-year-old female who presented with subcutaneous nodules on both upper arms. The light microscopic features were consistent with LEP, and the result of an immunofluorescence band test supported this diagnosis. A peculiar finding in this case was MCL in the subcutaneous tissue. Ultrastructurally, these were thin membranes without a tubular structure and tortuous thick membranes composed of minute tubules. The lesions were very similar to the fatty tissue changes in membranous lipodystrophy. On the other hand, the basement membranes of the blood vessels were thickened and multilayered, and the lumina were narrowed by endothelial swelling and thickening of the vessel wall. Our findings suggest that the MCL in LEP result from circulatory disturbance of the fat tissue.

The fate of hypodermis after liposuction surgery

Liposuction surgery can be viewed as a trauma to the hypodermis. With histologic, morphometric, and autoradiographic examination and the use of tritiated thymidine, uridine, and proline, we have studied the fate of adipose tissue at various intervals after liposuction; however, we have never seen a reparative proliferation of the residual lipocytes. Moreover, the metabolic activity of adipocytes apparently is not increased. Inflammatory reaction is minimal in the early weeks, but fibrosis takes place in some lobules of the hypodermis. Our data support the view that liposuction has a long-term effect on the structure of the hypodermis, without any stimulation in the proliferative and biosynthetic activity of residual adipocytes.

Lipomembranous changes in chronic panniculitis

The clinical and histopathologic findings in 13 patients with lipomembranous changes in the subcutaneous adipose tissue as part of the inflammatory reaction are presented. Nine patients had clinical evidence of vascular disease and four had clinical evidence of connective tissue disease. Histopathologic evidence of endarteritis obliterans, venous stasis, and hemorrhage was present in more than half the patients, and the clinical lesion of liposclerosis was frequently present. These findings suggest that the histologic changes of lipomembranous panniculitis may be the result of an inflammatory reaction in patients who have the liposclerosis of venous insufficiency with connective tissue disease or previous leg ischemia or both.