Cutaneous lipomatous neurofibroma: characterization and frequency

Cutaneous Neurofibroma Heterogeneity: Factors that Influence Tumor Burden in Neurofibromatosis Type 1

Neurofibromatosis type 1 is one of the most common genetic disorders of the nervous system and predisposes patients to develop benign and malignant tumors. Cutaneous neurofibromas (cNFs) are NF1-associated benign tumors that affect nearly 100% of patients with NF1. cNFs dramatically reduce patients' QOL owing to their unaesthetic appearance, physical discomfort, and corresponding psychological burden. There is currently no effective drug therapy option, and treatment is restricted to surgical removal. One of the greatest hurdles for cNF management is the variability of clinical expressivity in NF1, resulting in intrapatient and interpatient cNF tumor burden heterogeneity, that is, the variability in the presentation and evolution of these tumors. There is growing evidence that a wide array of factors are involved in the regulation of cNF heterogeneity. Understanding the mechanisms underlying this heterogeneity of cNF at the molecular, cellular, and environmental levels can facilitate the development of innovative and personalized treatment regimens.

Histopathological Variants of Cutaneous Neurofibroma: A Compendious Review

The first description of histopathological variants of neurofibroma dates back to 1994. Over the years, many individual case reports elucidating unusual histologic features in neurofibroma have been added to the literature, some of which have defined criteria, with the others falling under the roof of benign neural neoplasms. These unusual features, which sometimes may lead to pauses in identifying a common benign tumor such as neurofibroma. Awareness of these variants may help dermatopathologists avoid misinterpretation. Thus, this review aims to summarize all novel and unusual histopathological variants of cutaneous neurofibroma reported to date, in addition to any unusual variants that we encountered in our practice.

Prevalence and clinicopathological characteristics of lipomatous neurofibromas in neurofibromatosis 1: An investigation of 229 cutaneous neurofibromas and a systematic review of the literature

BACKGROUND

Lipomatous neurofibroma (Lnf) is a histopathological variant with adipocytes noted among cells of cutaneous neurofibromas. We aimed to investigate the prevalence and clinicopathological features of Lnfs of neurofibromatosis 1 (NF1)-associated cutaneous neurofibromas and to review the literature systematically. We also evaluated the expression of leptin (a hormone involved in lipid metabolism) in neurofibromas to better understand the pathogenesis of Lnfs.

METHODS

A prospective histologic study was conducted on 229 cutaneous neurofibromas from 85 NF1 individuals. Leptin expression was immunohistochemically evaluated in 111 cutaneous neurofibromas. To systematically review the literature, two authors independently performed literature searches without year restriction.

RESULTS

Forty (17.5%) neurofibromas were lipomatous. Lnfs were significantly larger lesions and associated with females. Eighteen (7.9%) of all neurofibromas had multinucleated floret-like giant cells, and these were associated with Lnfs. All neurofibromas expressed leptin. We systematically reviewed 13 articles. Three large studies investigated Lnfs mainly in sporadic neurofibromas and suggested that 0.3% to 8.0% of tumors (NF1 and sporadic) are Lnfs.

CONCLUSION

In NF1, Lnfs are common, mainly in larger tumors and women. All cutaneous NF1-neurofibromas express leptin. It is unknown if the expression of leptin accounts for the lipomatous variant, but it may have a role in the pathogenesis of cutaneous neurofibroma.

Cutaneous neurofibromas

Objective

To present the current terminology and natural history of neurofibromatosis 1 (NF1) cutaneous neurofibromas (cNF).

Methods

NF1 experts from various research and clinical backgrounds reviewed the terms currently in use for cNF as well as the clinical, histologic, and radiographic features of these tumors using published and unpublished data.

Results

Neurofibromas develop within nerves, soft tissue, and skin. The primary distinction between cNF and other neurofibromas is that cNF are limited to the skin whereas other neurofibromas may involve the skin, but are not limited to the skin. There are important cellular, molecular, histologic, and clinical features of cNF. Each of these factors is discussed in consideration of a clinicopathologic framework for cNF.

Conclusion

The development of effective therapies for cNF requires formulation of diagnostic criteria that encompass the clinical and histologic features of these tumors. However, there are several areas of overlap between cNF and other neurofibromas that make distinctions between cutaneous and other neurofibromas more difficult, requiring careful deliberation with input across the multiple disciplines that encounter these tumors and ultimately, prospective validation. The ultimate goal of this work is to facilitate accurate diagnosis and meaningful therapeutics for cNF.

Nonepithelial Tumors and Tumor-like Lesions of the Skin and Subcutis in Children

This overview of mesenchymal tumors presenting in the skin and/or subcutis in children brings together the range of neoplasms and hamartomas which are seen in this age-group. It is not surprising from the perspective of the pediatric or general surgical pathologist that vascular anomalies, including true neoplasms and vascular malformations, are the common phenotypic category. Since there is considerable morphologic overlap among these lesions, clinicopathologic correlation may be more important than for many of the other mesenchymal tumors. The skin and subcutis are the most common sites of clinical presentation for the infantile myofibroma which is the most common of fibrous mesenchymal tumors in children. Several of the other mesenchymal tumors are more common adults-like dermatofibrosarcoma protuberans, but nonetheless have an important presence in children, even as a congenital neoplasm. A lipomatous tumor in a young child should be considered as a possible manifestation of an overgrowth syndrome.

Liponeurofibroma: Clinicopathological features and histogenesis

A neurofibroma is a common cutaneous benign tumor of neural origin. Various histological variants have been reported. Recently, sporadic reports of fatty variants have been reported but their clinicopathological features have not been well studied. The purpose of this study was to examine liponeurofibroma, and to report the distinctive clinicopathological features and histogenesis in comparison with the classic form. A retrospective study was performed on 130 cases. Immunohistochemical staining was performed for S100, factor VIIIa, perilipin and vascular endothelial growth factor. Masson's trichrome stain was also used. Intratumoral adipocytes were examined with transmission electron microscopy. Thirty-two (24.6%) cases were classified as liponeurofibroma on microscopic examination. This variant was more common in patients with neurofibromatosis type 1, older age and female sex. The most prevalent location was the head and neck. Intratumoral fat deposits showed differences in morphology and size compared with subcutaneous fat on light microscopy. Neurofibromatosis type 1 had the highest odds of fatty change in liponeurofibroma. In sporadic cases, fatty change can be caused by senescence, chronic injury, or tissue hypoxia secondary to internal or external stimuli. Further investigation is needed to identify the pathomechanism of fatty change in various cutaneous neoplasms, including neurofibroma.

Pathology of Melanotic Schwannoma

CONTEXT.—

Melanotic schwannoma (MS) is a nerve sheath tumor with a uniform composition of variably melanin-producing Schwann cells and metastatic potential. The MS is an uncommon neoplasm, accounting for less than 1% of all nerve sheath tumors, with a predilection for spinal nerve involvement. Microscopically, the tumors are characterized by spindle and epithelioid cells arranged in interlacing fascicles, with marked accumulation of melanin in neoplastic cells and associated melanophages. The MSs are frequently associated with Carney complex, showing features of psammoma bodies and adipose-like cells. Strict criteria of malignancy in MS are not well developed, although a combination of worrisome histologic features (large, vesicular nuclei, with macronucleoli, brisk mitotic activity, and necrosis) raises concern for aggressive behavior.

OBJECTIVE.—

To review the current status of the MS literature, discussing putative etiology, histopathology, current genetics, and differential diagnoses, including overlap with other pigmented tumors.

DATA SOURCES.—

Search of PubMed (National Center for Biotechnology Information, Bethesda, Maryland) and the authors' own experiences.

CONCLUSIONS.—

The occurrence of MS at several unusual anatomic sites and its spectrum of morphologic patterns can result in significant diagnostic difficulty, and correct diagnosis is particularly important because of its high tendency to recur locally and to metastasize, which highlights the importance of diagnostic recognition, ancillary molecular genetic testing, and close clinical follow-up of patients with MS.

Recurrent Diffuse Neurofibroma of Nose Associated with Neurofibromatosis Type 1: A Rare Case Report with Review of Literature

Diffuse neurofibroma is an unusual variant of neurofibroma with the head and neck being the common sites of involvement. It is benign in nature and spreads superficially and has many ectatic blood vessels. Histologically it is similar to conventional neurofibromas except for a few peculiar distinguishing features. We report a case of a 14-year-old boy who presented with a diffuse recurrent painless swelling over the dorsum of the nose with the clinical stigmata of neurofibromatosis. Microscopy revealed a diagnosis of diffuse neurofibroma with a few foci showing differentiation towards Meissner's type of tactile corpuscles. It is important to recognize this entity as it has a tendency to recur, yet hardly ever become malignant and is almost always associated with neurofibromatosis type 1.

Lipomatous Change in Uveal Melanoma: Histopathological, Immunohistochemical and Cytogenetic Analysis

PURPOSE

The aim of this study was to describe a case of lipomatous change in uveal melanoma.

PROCEDURES

The patient presented with a 2-year history of blurry vision. A full examination of the right eye revealed a dome-shaped pigmented subretinal mass in the choroid with a thickness of 9 mm and a diameter of 15 mm. The eye was enucleated and prepared for histopathologic, genetic and molecular investigation.

RESULTS

Histopathology revealed a small circumscribed area consisting of mature adipocytic appearing cells with abundant clear cytoplasm and small peripheral flattened nuclei within a spindle-cell melanoma of the uvea. The cytoplasm of the adipocytic cells stained negative for periodic acid-Schiff and Alcian blue and positive for Melan-A, HMB-45 and tyrosinase, confirming melanocytic lineage. Fluorescence in situ hybridization analysis confirmed trisomy of chromosome 6p22 and disomy of chromosome 3p13 in the nuclei of both the tumor spindle type B cells and in the nuclei of lipomatous tumor cells.

CONCLUSIONS

Lipomatous change can be added to the many histopathologic faces of uveal melanoma. To our knowledge, this is the first report of lipomatous change in uveal melanoma performed with cytogenetic investigations.

Spindle Cell Lipoma Occurring in the Buccal Mucosa: An Unusual Location of This Benign Lipomatous Neoplasm

Spindle cell lipoma is a benign lipomatous neoplasm, which rarely occurs in the oral cavity. The aims of this paper are to report a case of spindle cell lipoma located in buccal mucosa and discuss the main clinical, histological, and immunohistochemical findings of this entity. Thus, we report a 4-year history of an asymptomatic smooth surface nodule in an elderly Caucasian man with clinical hypothesis of fibroma. The histopathological examination showed spindle cells, mature adipose tissue, and many mast cells in a stroma of connective tissue presenting ropey collagen fibers bundles. After immunohistochemical analysis, the final diagnosis was spindle cell lipoma.

Cutaneous microcystic/reticular schwannoma: a poorly recognized entity

BACKGROUND

Microcystic/ reticular schwannoma is exceptionally rare yet distinctive morphological variant of schwannoma with predilection for visceral sites lacking association with neurofibromatosis.

AIMS

To further delineate clinicopathological features of cutaneous microcystic/reticular schwannoma and to discuss its differential diagnosis.

RESULTS

We analyzed three cutaneous microcystic/reticular schwannomas, occurring in two males and one female (mean age: 37.6 years). The tumors presented as a non-painful slightly raised papule (mean: 0.7 cm) on upper arm (n = 2) and back (n = 1). No recurrences were observed despite marginal excision (mean follow up: 42 months). Histopathologically, a multilobular proliferation was present in the dermis composed of bland tumor cells forming distinctive microcystic, reticular, lace-like or pseudoglandular structures, containing abundant myxoid/mucinous material. By immunohistochemistry, tumor cells lining microcystic structures corresponded to Schwann cells (diffuse S100 positive, variable GFAP positivity). A discontinuous EMA-positive perineurium was present at the periphery of some of the lobules.

CONCLUSION

Cutaneous microcystic/reticular schwannoma expands the spectrum of benign peripheral nerve sheath tumors with reticular morphology encountered in the skin. Other tumors in this group include reticular perineurioma and hybrid tumors with reticular morphology, e.g. reticular perineurioma/schwannoma and reticular perineurioma/neurofibroma.

Lipomatous neurofibromas with giant pigmented lesion

Neurofibroma is the most common benign neural tumour. Among the large number of histopathological variants reported, lipomatous neurofibroma is exceedingly infrequent, and shows the presence of intratumoral adipocytes admixed with spindle cells in the dermis. We present a case of a 37-year-old man with lipomatous neurofibromas associated with a giant garment-like pigmented lesion involving his lower trunk and right thigh.

Posterior mediastinal ganglioneuroma with peripheral replacement by white and brown adipocytes resulting in diagnostic fallacy from a false-positive 18F-2-fluoro-2-deoxyglucose-positron emission tomography finding: a case report

Introduction

Ganglioneuroma is a rare tumor in the posterior mediastinum; fat-containing ganglioneuromas are rarely reported. The present case report documents a brown fat-containing, posterior mediastinal ganglioneuroma, which has not been reported previously. Radiological examination, in particular 18F-2-fluoro-2-deoxyglucose-positron emission tomography, suggested that the tumor had low-grade malignant potential. This led to uncertainty at preoperative diagnosis.

Case presentation

An asymptomatic 66-year-old Japanese woman with no significant past medical history was referred for the evaluation of a posterior mediastinal mass. Although its size had not changed in the past 5 years, a malignant lipomatous tumor could not be excluded due to the presence of intratumoral fat and increased 18F-2-fluoro-2-deoxyglucose uptake observed by positron emission tomography imaging. A computed tomography-guided core-needle biopsy revealed a mixture of mature adipocytes, spindle-shaped cells, and fibrotic stroma. Definite diagnosis was not possible, and surgical resection was performed. Three years after the surgery, she remains disease-free.

Conclusions

Histological diagnosis of the surgically resected mass confirmed ganglioneuroma with substantial amounts of white and brown adipose tissues in peripheral areas. The existence of both ganglion cells and brown fat tissue intensified the accumulation of 18F-2-fluoro-2-deoxyglucose, resulting in a false-positive result by positron emission tomography. Considering this, ganglioneuroma should not be excluded either clinically or pathologically in fat-containing, posterior mediastinal tumors.

[A rare case of pharyngeal mesenchymoma demonstrating a variety of histopathological findings]

We encountered a 38-years-old female patient who was complaining of an unpleasant sensation of the left cervical area due to a recurrent tumor originating from the middle pharynx. She had a history of surgically resected neurofibroma and lipoma from the anterior oropharyngeal wall respectively 5 years and 11 years previously. The preoperative diagnosis of a benign, non-epithelial neoplasm was made based on the imaging studies and surgical treatment was scheduled. An extended surgical resection of the middle pharynx including normal mucosa and a part of the tongue base was successfully accomplished. To cover the pharyngeal defect, a right antero-lateral thigh musculo-cutaneous flap was used for reconstruction. Microscopically, the surgically resected tissue showed a mixed condition of mature cartilaginous, bony and fibroadipose tissue without atypia. The final diagnosis was a benign mesenchymoma which was thought to have developed from pluripotential mesenchymal cells. We considered that the past tumorous lesions had possibly originated in those cells. Because pluripotential mesenchymal cells cannot easily be identified with ordinary histopathological examination, the determination of optimal surgical margins is difficult. In the case of mesenchymoma, substantial marginal tissue should be resected in order to prevent recurrence even in the case of a pathologically-proven benign tumor.

Fibrolipomatous Hamartoma of the Nerve Arising in the Neck: A Case Report With Review of the Literature and Differential Diagnosis

We report an unusual case of a fibrolipomatous hamartoma that arose in a nuchal nerve. Typically, fibrolipomatous hamartoma, otherwise known as a neural fibrolipoma or lipomatosis of nerve, arises in the median nerve, brachial plexus, cranial nerves, or plantar nerves. The differential diagnosis is broad and includes benign and malignant spindle cell lesions, such as spindle cell lipoma, perineurioma, and myxoid liposarcoma. We were able to identify the lesion based on the typical histology, including triphasic composition with spindle cell, neural, and adipocytic components and whorled architecture. Because of the atypical location in the neck, detailed immunohistochemical staining was performed. The lesional spindle cells were negative for SMA, CD10, CD68, EMA, S100, PGP9.5, CD34, CD56, and beta-catenin. Colloidal iron stain highlighted marked intralesional mucin deposition. This detailed immunohistochemical profile is a useful diagnostic aid and to our knowledge has not been previously described.

Hemifacial mass with extensive intralesional ossification and fat

The imaging appearance of neurofibromas is well described; however, macroscopic fat in a neurofibroma has been sparsely reported and intralesional ossification has only been documented twice in the literature. We describe a diffuse neurofibroma presenting as a hemifacial mass, atypical for the presence of extensive intralesional ossification and fat; the diagnosis was suggested on identification of other associated radiological features of neurofibromatosis.

Multinucleate giant cells in neurofibromas: a clue to the diagnosis of neurofibromatosis

BACKGROUND

A 54-year-old African-American male patient underwent removal of several cutaneous neurofibromas. Histopathologic examination revealed a nonencapsulated, haphazardly arranged proliferation of slender spindle cells in a myxoid stroma consistent with neurofibroma. Interestingly, each specimen exhibited numerous, large, multinucleate giant cells with nuclei arranged in a wreath-like or linear pattern. Immunoperoxidase staining revealed these cells to be negative with S-100 and CD-34. It was subsequently learned that this patient has neurofibromatosis type 1 (NF1).

METHODS

A retrospective review of all lesions coded as neurofibroma from our institution between 1 June 2006 and 28 August 2006 was performed.

RESULTS

Biopsies of 53 cutaneous neurofibromas from 51 patients were reviewed. In these, multinucleate giant cells were present in only three (5.7%), all in patients with single lesions.

CONCLUSIONS

Although the incidence of floret-like giant cells in neurofibromas of patients with NF1 is unknown, our findings suggest that the presence of these cells might be a clue to the presence of NF1.

Multinucleated floret-like giant cells in sporadic and NF1-associated neurofibromas: a clinicopathologic study of 94 cases

Multinucleated floret-like giant cells (MNFGCs), similar to those commonly observed in pleomorphic lipoma and giant cell fibroblastoma, have been occasionally reported in gynecomastia and neurofibromas from patients affected by neurofibromatosis type 1 (NF1). Accordingly, it has been suggested that their detection, especially in an otherwise typical neurofibroma, could be a morphological clue to diagnosis of NF1. The aim of the present study was the identification of MNFGCs in a large series (94 cases) of sporadic and NF1-associated neurofibromas, to assess if their presence may indeed be a morphological marker of NF1. Numerous MNFGCs, namely, those that were easily apparent at low magnification (x50 and x100), were identified only in 5.3% of cases. In 18.1% of cases, a low number of these cells could be observed but only after a careful search, especially at higher magnification (x200 and x400). Immunohistochemically, all MNFGCs were stained with vimentin and CD34, but not with S-100 protein. Interestingly, there was no statistically significant correlation between MNFGCs (presence or absence) and NF1 (p = 0.73), gender (p = 0.59), age (p = 0.43), and site of tumor (cutaneous vs deep-seated soft tissue; p = 0.27). Our clinicopathologic findings suggest that MNFGCs in an otherwise typical neurofibroma are not a reliable marker of NF1, likely representing a morphological reactive change of the indigenous dermal or endoneurial fibroblasts or dendritic cells in response to unknown microenvironmental stimuli.