Retroperitoneal malignant meningioma. A light microscopic, immunohistochemical, and ultrastructural study

Malignant perineurioma derived from the retroperitoneum with an aggressive clinical course: a case report

BACKGROUND

Malignant perineurioma is a rare malignant counterpart of perineurioma derived from perineural cells. Resection is the primary option for the treatment of malignant perineuriomas; however, patients often develop recurrence after resection, and effective treatment for advanced or recurrent lesions needs to be established. This report describes a 51-year-old female with a rare malignant perineurioma in the retroperitoneum, which contributing valuable insights to the literature.

CASE PRESENTATION

The patient presented with abdominal distension and the imaging work-up revealed a huge hemorrhagic tumor in the retroperitoneum and obstruction of inferior vena cava by the tumor. The patient underwent surgery retrieving the tumor combined with left hemiliver and retrohepatic vena cava, which confirmed the diagnosis of a malignant perineurioma based on histopathological and immunohistochemical examination. Cancer gene panel testing identified mutations in NF2. Radiotherapy was administered for peritoneal dissemination 2 months after surgery, and the patient died from disease progression 6 months after surgery.

CONCLUSIONS

This rare case highlights the challenges in managing retroperitoneal malignant perineuriomas. The aggressive characteristics and limited treatment options for advanced malignant perineuriomas underscore the need for understanding the pathogenesis and developing effective systemic therapies. The identification of an NF2 mutation provides significant insights into potential therapeutic target.

Primary follicular dendritic cell sarcoma of the kidney - a case report of a rare tumor with emphasis on diagnostic pitfalls

BACKGROUND

Follicular dendritic cell sarcoma (FDCS) is a rare low-grade tumor of the lymph nodes, but roughly one-third of the cases emerge from extranodal sites, posing diagnostic challenges.

CASE PRESENTATION

In this report, we present the case of a 59-year-old lady who complained of renal colic. During investigation, a kidney tumor was discovered. A radical nephrectomy was performed, and histological examination identified the tumor as a sarcomatoid renal cell carcinoma. The case was then referred to a genitourinary pathologist for further evaluation. The tumor cells exhibited positive staining for CD21, CD23, somatostatin receptor 2 A, and MDM2 expression. Additionally, MDM2 gene amplification was confirmed by the FISH study. Ultimately, the tumor was diagnosed as a primary renal FDCS. The patient was placed under active oncological surveillance and did not receive any further therapy. Remarkably, after 91 months of follow-up, she remains tumor-free.

CONCLUSION

This case represents a well-documented primary renal FDCS. Our aim in presenting this extremely rare tumor is to enhance awareness and highlight the importance of considering FDCS in the differential diagnosis.

Primary ectopic meningioma in the thoracic cavity: A rare case report and review of the literature

Background

Meningioma is a common type of intracranial tumor in adults. It rarely arises in the chest, with only a few case reports in the English literature. Here, we report the case of a patient with a primary ectopic meningioma (PEM) located in the thoracic cavity.

Case presentation

A 55-year-old woman presented with exercise-induced asthma, chest tightness, intermittent dry cough and fatigue for several months. Computed tomography revealed the presence of a huge mass in the thoracic cavity, with no connection to the spinal canal. Lung cancer and mesothelioma were suspected, and surgery was performed. Grossly, the mass was a grayish-white solid 9.5 cm × 8.4 cm × 5.3 cm in size. The microscopic morphology of the lesion was consistent with that of typical central nervous system meningioma. The pathological subtype was transitional meningioma. The tumor cells were arranged in a fascicular, whorled, storiform and meningithelial pattern, with occasional intranuclear pseudo-inclusions and psammoma bodies. In focal areas tumor cells were considerably dense, and the cells were round or irregular in shape, with less cytoplasm, uniform nuclear chromatin, and visible nucleoli and mitoses (2/10 HPF). By immunohistochemistry, the neoplastic cells showed strong and diffuse staining with vimentin, epithelial membrane antigen and SSTR2 with variable expression of PR, ALK and S100 protein. However, the cells were negative for GFAP, SOX-10, inhibin, CD34, STAT6, smooth muscle actin, desmin, CKpan, D2-40, WT-1, CK5/6 and CD45. The highest proliferation index by Ki-67 was 15%. The abnormal expression of ALK led to the initial misdiagnosis of an inflammatory myofibroblastic tumor. After 12 months of follow-up, no disease progression was observed.

Conclusion

The presence of primary ectopic meningiomas in the thoracic cavity is extremely rare, and this tumor is easily misdiagnosed clinically. Imaging is suggested to determine the location and possible differential diagnosis, while the final diagnosis should be via pathological examination. Immunohistochemistry is crucial for disease diagnosis. Owing to our limited knowledge of PEM, its pathogenesis and tissue of origin remain unclear. Clinicians should pay close attention to such potential patients. The present case report may provide insights into the diagnosis and therapy of patients with this tumor.

Primary Extracranial Meningiomas of the Head and Neck

Meningiomas represent the most common benign histological tumor of the central nervous system. Usually, meningiomas are intracranial, showing a typical dural tail sign on brain MRI with Gadolinium, but occasionally they can infiltrate the skull or be sited extracranially. We present a systematic review of the literature on extracranial meningiomas of the head and neck, along with an emblematic case of primary extracranial meningioma (PEM), which provides further insights into PEM management. A literature search according to the PRISMA statement was conducted from 1979 to June 2021 using PubMed, Web of Science, Google Scholar, and Scopus databases, searching for relevant Mesh terms (primary extracranial meningioma) AND (head OR neck). Data for all patients were recorded when available, including age, sex, localization, histological grading, treatment, possible recurrence, and outcome. A total of 83 published studies were identified through PubMed, Google Scholar, and Scopus databases, together with additional references list searches from 1979 to date. A total of 49 papers were excluded, and 34 manuscripts were considered for this systematic review, including 213 patients. We also reported a case of a 45-year-old male with an extracranial neck psammomatous meningioma with sizes of 4 cm × 3 cm × 2 cm. Furthermore, whole-body ⁶⁸Ga-DOTATOC PET/CT was performed, excluding tumor spread to other areas. Surgical resection of the tumor was accomplished, as well as skin flap reconstruction, obtaining radical removal and satisfying wound healing. PEMs could suggest an infiltrative and aggressive behavior, which has never found a histopathological correlation with a malignancy (low Ki-67, <5%). Whole-body ⁶⁸Ga-DOTATOC PET/CT should be considered in the patient’s global assessment. Surgical removal is a resolutive treatment, and the examination of frozen sections can confirm the benignity of the lesion, reducing the extension of the removal of healthy tissue surrounding the tumor.

Dedifferentiated Liposarcoma With Meningothelial-Like Whorls: Five Additional Cases and Review of the Literature

Background. Diagnosis of dedifferentiated liposarcoma (DDL) can sometimes be challenging due to a wide variety of histological features. "Meningothelial-like" whorl is an uncommon histological feature of DDL, which is also observed in neural tumors and follicular dendritic cell sarcoma. This feature is frequently associated with metaplastic bone formation. We conducted this study to describe the clinicopathological features of DDL with meningothelial-like whorls that would aid in establishing accurate diagnosis. Material and Methods. Microscopic glass slides of 5 cases of DDL with meningothelial-like whorls, diagnosed between January 2010 and December 2019, were reviewed. Results. Paratesticular region was the most common site. Whorls occupied 10% to 75% of tumor area and ranged in size from <0.1 cm to >2 cm. In 1 case, these whorls coalesced to form large areas of dedifferentiation. The cells forming whorls were spindle to epithelioid shaped and lacked significant nuclear pleomorphism and increased mitoses. Metaplastic bone formation was observed in 4 cases and cartilage formation in 3 cases. p16 and α-smooth muscle actin (α-SMA) immunohistochemical stains were positive in 2 cases, when performed. MDM2 gene amplification was observed in all cases by fluorescence in situ hybridization technique. These tumors showed aggressive behavior, similar to that of DDL without meningothelial-like whorls. Two patients died, 1 developed recurrence, 1 presented as recurrent tumor, and 1 developed metastasis. Conclusion. Meningothelial-like whorls in DDL most likely represent an early stage of dedifferentiation. Presence of well-differentiated liposarcoma areas, metaplastic bone formation, positive expressions for p16 and α-SMA immunohistochemical stains, and MDM2 gene amplification are useful diagnostic clues. These tumors have the potential to behave aggressively.

A contemporary and a historical patient with an ectopic meningioma

Introduction: Ectopic meningiomas are rare tumors which can be encountered by all surgical specialties. Patients and methods: We report on two different cases, a contemporary one and a historical one, highlighting the diversity of clinical presentations and prognoses of these lesions. Furthermore epidemiological aspects, clinical features, and diagnostic and therapeutic work-up in patients with an ectopic meningioma are reviewed. Results: Typically, ectopic meningiomas present as gradually expanding lesions, causing a variety of symptoms by their mass effect. Diagnosis is based on histological characteristics, which are similar to those of intracranial meningiomas. Treatment is primarily surgical. Conclusions: The cases we report are at different ends of the clinical and prognostic spectrum. Therapeutic options for different clinical scenarios are discussed.

Primary Pulmonary Meningioma: Report of a case and Review of the Literature

Primary pulmonary meningiomas are rare and their occurrence has been reported only sporadically. The diagnosis of such tumors should be accepted only after the presence of an intracranial or intraspinal meningioma has been excluded. The morphological and immunohistochemical features are similar to those of intracranial meningiomas. A case of primary pulmonary meningioma along with a review of the literature and discussion of other lesions in the differential diagnosis of this rare neoplasm are here presented.

Cytomorphology of Recurrent Osseous Extracranial Meningioma of Right Pubic Ramus:: Report of a Case and Literature Review

Meningiomas are well-recognized neoplasms of the central nervous system. Primary extracranial meningiomas (ECMs) are extremely rare and arise in various anatomic sites. We present a 56-year-old female with 13-year history of primary grade I meningothelial meningioma of right pubic symphysis, orthotopic heart transplant, and right total hip arthroplasty, who presented with progressive right hip pain for 3 weeks. Primary intracranial, intraspinal and other tumors were excluded. Imaging revealed a destructive lytic lesion at right superior and inferior pubic rami and body, associated with extensive bone destruction and soft tissue mass. Touch imprint (TI) cytology of computed tomography (CT)-guided core biopsy from the right pubic ramus (PRA) lesion showed a spindle cell neoplasm, with classical syncytial, lobular, and whorling cellular arrangement, composed of spindle, oval or round nuclei with occasional pseudoinclusions, consistent with known history of osseous meningioma. Tumor was further characterized by histopathology as grade 1 meningioma with meningothelial features. To our knowledge, primary osseous ECM arising specifically at the PRA has not been reported previously. ECM at this site may pose a diagnostic challenge for cytologists as its features may resemble other more commonly observed lesions. Accurate diagnosis requires awareness of occurrence of ECM at PRA and recognition of its characteristic cytomorphology. TI cytological features of our case are presented and previously described cytology of ECMs and diagnostic pitfalls are reviewed. Diagn. Cytopathol. 2016;44:618-622. © 2016 Wiley Periodicals, Inc.

Primary ectopic atypical meningioma in the renal hilum: a case report

BACKGROUND

Primary ectopic atypical meningioma involving the renal hilum is rare. This is, to our knowledge, only the second case report of a primary retroperitoneal meningioma and the first case of an atypical subtype in this location.

CASE PRESENTATION

A 53-year-old Han Chinese man presented with a 2-year history of left-side flank pain. An oval-shaped retroperitoneal mass was found in the left renal hilum on computed tomography, which was resected en bloc along with the kidney via laparotomy. According to the World Health Organization criteria, the tumor was histopathologically classified as a meningioma (Grade II, atypical). Five years later, the tumor recurred at the primary site with a similar histopathology. The patient received palliative resection, followed by radiotherapy (4500 cGy in 25 fractions). No relapse was found at 6-month follow-up.

CONCLUSION

We describe the clinical, radiographic and histopathological features of an unusual case of aggressive ectopic meningioma in the renal hilum. The patient presented with a massive retroperitoneal tumor without primary cerebral or secondary metastatic lesions; the preoperative diagnosis was naturally confined to the common retroperitoneal malignancies. This case is of interest to oncologists, because of both its rare location and aggressiveness; it not only enriched the spectrum of primary ectopic meningioma, but also reminded us of potential recurrence of an atypical meningioma. This case raises the issue of the etiology of such a rare tumor that needs further investigation, and more importantly demands long-term follow-up result.

Primary pulmonary malignant meningioma with lymph node and liver metastasis in a centenary woman, an autopsy case

Primary meningiomas arising outside the central nervous system are very rare. They have been reported in the head and neck region, in the thorax, the retroperitoneum, and the pelvis. Usually, they behave as slow-growing tumors with a good prognosis. Herein, we report an autopsy case of a 108-year-old woman, known for a right-sided slowly growing lung nodule for 39 years. Death was attributed to cachexia. At post-mortem, a 15-cm mass was present in the right inferior lobe of the lung, associated with an ipsilateral hilar lymphadenopathy, and another 10-cm mass in the liver. Histology revealed a WHO grade III meningioma. No tumor was observed in the cranial cavity. This case illustrates a rare location of meningioma and highlights its biological behavior, with a very slow progression from a most probably benign tumor to a malignant lesion with metastasis over four decades.

Meningioma of the scapula

Meningiomas account for approximately 15% of all intracranial tumors and are the most common non-glial primary tumors of the central nervous system. Most meningiomas are benign neoplasms with characteristic imaging features. Primary extradural meningiomas account for only 1-2% of all meningiomas. They must be differentiated from intradural meningiomas with secondary extradural extension and/or metastases. The vast majority of extradural meningiomas are found in the skull or in the head and neck region. We report on an extremely rare case of primary extradural meningioma that was located in the scapula. The lesion was resected. Radiographic findings and pathologic features are discussed. To the best of our knowledge, this form of presentation of an extradural meningioma has not been previously described.

A case of neck ectopic meningioma

Primary extra cranial and extra spinal meningioma is rare and is usually limited to the head and neck region or to the paravertebral soft tissues. Histologic diagnosis (in particular for fresh specimens) is often difficult. A 16-year-old girl with a cervical mass is presented. It was a relatively large mass with an approximate diameter of 5 cm. It was diagnosed in fine needle aspiration as a pleomorphic adenoma. Intra-operative diagnosis was paraganglioma and frozen section suggested an infiltrative tumor. Histologically, the lesion showed uniform spindle cell proliferation separated by hyalinized collagen bundles. The cells were often arranged in sweeping fascicles and concentrically wrapped in tight whorls. Immunohistochemically, tumor cells were positive for epithelial membrane antigen and vimentin, while showing no reaction for cytokeratin, chromogranin, neuron-specific enolase and thyroglobulin. A diagnosis of ectopic meningioma was established based on microscopic appearance and immunohistochemical profile of the tumor. Despite its rarity, ectopic meningioma should be considered in differential diagnosis of any mass lesion in head and neck regions, containing spindle cells.

Extracranial meningioma in the vicinity of the temporal bone: a difficult preoperative diagnosis

BACKGROUND

Extracranial meningioma is a rare tumor, and most of the time only after histopathologic examination is diagnosis possible.

CASE DESCRIPTION

A 40-year-old right-handed woman presented with progressive swelling over the right side of the forehead and temporal region associated with proptosis and visual loss. Incisional biopsy of the lesion was reported as spindle cell tumor. Computed tomography scan showed large enhancing predominantly extracranial lesion located in the right anterior frontotemporal region extending into the infratemporal fossa and a relatively thin sheet of tumor on the intracranial aspect of the thickened temporal. Intraoperative impression was malignant tumor involving the temporalis muscle, and a near total excision of the lesion was performed. Histopathologic features were suggestive of meningothelial meningioma arising from the temporal bone with predominant extracranial extension.

CONCLUSION

Preoperative suspicion of a meningioma in this patient would have resulted in a more aggressive surgical approach as these lesions are relatively benign with indolent course.

Primary extracranial meningioma of the pelvis: a light microscopic, immunohistochemical, and ultrastructural study

BACKGROUND

Extracranial meningiomas are rare tumors which have been described in head and neck. The occurrence in mediastinum and retroperitoneum is even rarer. This presented case records a unique location, a meningioma arising in pelvis.

CASE

A 52-year-old woman presented with an ovarian mass. The histology of the resected tumor revealed sheets of bland epithelioid cells arranged in prominent whorls with psammoma bodies typical of meningothelial meningioma. Immunohistochemical analysis demonstrated diffuse strong positivity for vimentin and epithelial membrane antigen (EMA). There was moderate reactivity for cytokeratin, estrogen (ER) and progesterone (PR) receptors. By electron microscopy, the tumor cells expressed desmosomes and abundant intermediate filaments.

CONCLUSION

According to our review of literature, this is the first reported case of a primary pelvic meningioma. Its benign appearance and 4-year disease-free survival without clinical or radiological evidence of intracranial disease favors the pelvis as the primary site.

Ectopic neural and neuroendocrine neoplasms

Although neural and neuroendocrine tissues are distributed virtually ubiquitously throughout the body, the occurrence of selected neoplasms related to those lineages is extremely uncommon in some topographic sites. This review considers the clinicopathologic characteristics of heterotopic pituitary adenomas; neuroendocrine carcinomas in non-organ-based locations; ectopic (extraneuraxial) meningiomas and gliomas; visceral neuroblastic neoplasms and primitive neuroectodermal tumors; and paragangliomas arising outside the sympathoadrenal neural network. Practical approaches to differential diagnosis are emphasized.

Seeding of malignant meningioma along a surgical trajectory on the scalp. Case report and review of the literature

The authors report the case of an 11-year-old boy with a malignant meningioma of the right frontal meninges. The tumor was asymptomatic, despite visible exophytic extracranial growth. Neuroimaging demonstrated an en plaque meningioma bulging into the brain. Six months after the tumor had been totally removed by surgery, an isolated subcutaneous metastasis developed at the right preauricular area of the scalp, originating at the scar left by the first surgery. After removal of this metastasis, radiotherapy was conducted. To date the follow-up examinations have not revealed any additional metastases. To the best of the authors' knowledge, this is the first report of a seeding of a subcutaneous metastasis in a child with a malignant meningioma. The authors review the literature with reference to malignant meningiomas and their formation of metastasis. In cases of malignant meningiomas, piecemeal tumor removal carries the risk of iatrogenic cell dissemination even when precautions are taken.

Extranodal follicular dendritic cell sarcoma of the head and neck region: three new cases, with a review of the literature

Extranodal follicular dendritic cell (FDC) sarcoma of the head and neck region is uncommon, with 16 well-documented cases previously reported (four in the tonsil, four in the pharynx, two in the palate, five in the soft tissue, and one in the thyroid). We here report an additional three cases of extranodal FDC sarcoma in the tonsil (two cases) and pharynx (one case). In these new cases, the neoplastic cells were arranged in diffuse, fascicular, and vaguely whorled growth patterns. A background lymphocytic infiltrate was sprinkled throughout the neoplasms, with focal prominent perivascular cuffing. Scattered multinucleated giant cells were present. Immunohistochemically, tumor cells were strongly and diffusely positive for follicular dendritic cell markers CD21 and CD35. Tumor cells were diffusely positive for fascin and negative for leukocyte common antigen, S-100 protein, cytokeratin, and Epstein-Barr virus (EBV) latent membrane protein-1 (EBV-LMP). EBV was also not detected in the tumor cells by in situ hybridization for EBV-encoded RNAs. FDC sarcomas are probably an underrecognized neoplasm, especially when they occur in extranodal sites in the head and neck region. Two of the three new cases we report were initially misdiagnosed, and five cases of extranodal FDC sarcoma in the head and neck region reported in the recent literature were initially misdiagnosed. Our aim is to complement the current understanding of this neoplasm and alert pathologists to this rare entity in this region to avoid misdiagnosis. Recognition of extranodal FDC sarcoma requires a high index of suspicion, but this tumor has numerous distinctive histological features that should bring the neoplasm into the differential diagnosis. Confirmatory immunohistochemical staining with follicular dendritic cell markers such as CD21 and/or CD35 is essential for the diagnosis. Correct characterization of this neoplasm is imperative given its potential for recurrence and metastasis.

Primary extradural meningiomas: a report on nine cases and review of the literature from the era of computerized tomography scanning

OBJECT

Primary meningiomas arising outside the intracranial compartment (primary extradural meningiomas [PEMs]) are rare tumors. To develop a better understanding of these tumors and to establish a comprehensive classification scheme for them, the authors analyzed a series of patients treated at the M. D. Anderson Cancer Center (MDACC) and reviewed all cases reported in the English-language literature since the inception of the use of computerized tomography (CT) scanning.

METHODS

Clinical records, results of radiographic studies, and histological slides were reviewed for all cases of PEM at MDACC. Demographic features, symptoms, tumor location, histological grade, and patient outcome were assessed in all cases. A comprehensive literature search identified 168 PEMs in 142 patients reported during the CT era. These reports were also analyzed for common features. Tumors for both data sets were classified as purely extracalvarial (Type I), purely calvarial (Type II), and calvarial with extracalvarial extension (Type III). Type II and Type III tumors were further categorized as convexity (C) or skull base (B) lesions. The incidence of PEMs at MDACC was 1.6%, which was consistent with the rate reported in the literature. In both data sets, the male/female ratio was nearly 1:1. The most common presenting symptom was a gradually expanding mass. The age of patients at diagnosis of PEM was bimodal, peaking during the second decade and during the fifth to seventh decades. In all MDACC cases and in 90% of those reported in the literature the PEMs were located in the head and neck. The majority of tumors originated in the skull (70%). In the MDACC series and in the literature review, the majority (67% and 89%, respectively) of tumors were histologically benign. Although fewer PEMs were malignant or atypical (33% at MDACC and 11% in the literature), their incidence was higher than that observed for primary intracranial meningiomas. Distant metastasis was not a common feature reported for patients with PEMs (6% in the literature). Outcome data were available in 96 of the cases culled from the CT-era literature. The combination of the MDACC data and the data obtained from the literature demonstrated that patients with benign Type IIB or Type IIIB lesions were more likely to experience recurrence than patients with benign Type IIC or Type IIIC tumors (26% compared with 0%, p < 0.05). The more aggressive atypical and malignant tumors were associated with a statistically significant higher death rate (29%) relative to benign tumors (4.8% death rate, p < 0.004).

CONCLUSIONS

Defining a tumor as a PEM is dependent on the tumor's relation to the dura mater and the extent and direction of its growth. Classification of PEMs as calvarial or extracalvarial and as convexity or skull base lesions correlates well with clinical outcome.

Primary pulmonary malignant meningioma

Fewer than 20 cases of primary pulmonary meningioma have been reported. Most of these cases have been histologically and clinically benign. We report an unusual case of primary pulmonary malignant meningioma with atypical histologic features and malignant behavior. A computed tomography scan of the head did not show evidence of tumor. The right upper lobe mass was resected and showed features of an atypical meningioma with loss of architectural pattern, mild nuclear pleomorphism, increased mitotic counts (up to 15 mitotic figures per 10 high power fields), and focally prominent nucleoli. Focally, cells with rhabdoid features were identified. The tumor's immunohistochemical and ultrastructural profiles were consistent with a meningioma. The tumor stained negative for estrogen and focally positive for progesterone receptors and had a MIB-1 labeling index (marker of cell proliferation) of 9.2%. Approximately 5 months after the initial resection, the patient experienced a tumor recurrence with multiple lymph node metastases, spread to the middle and lower lobes of the right lung, and metastasis to the diaphragm. Rarely, primary pulmonary meningiomas may present as high-grade malignant lesions.

Clear cell meningioma of the lumbo-sacral spine with chordoid features

Clear cell meningioma (CCM) is a peculiar variant that differs from conventional meningioma in affecting younger patients, arising more often in spinal or cerebellopontine locations, and showing a higher recurrence rate. Classical meningothelial areas are scarce in these tumors and the differential diagnosis with other neoplasms, particularly metastatic carcinoma, is often difficult. We report a case of clear cell meningioma from the lumbosacral spine in which location, radiologic presentation, light microscopic appearance in initial sampling, and some of the ultrastructural findings were reminiscent of chordoma. The tumor cells were diffusely positive for vimentin and very focally positive for epithelial membrane antigen. Ultrastructural demonstration of interdigitating cell processes joined by numerous desmosomes confirmed the diagnosis of CCM.

Liposarcoma with meningothelial-like whorls: a study of 17 cases of a distinctive histological pattern associated with dedifferentiated liposarcoma

AIMS

We reviewed 17 cases of liposarcoma with peculiar meningothelial-like whorls to determine the pathological and clinical significance of this distinctive morphological finding.

METHODS AND RESULTS

Seventeen liposarcomas with concentric whorls simulating the whorls seen in meningioma, were retrieved from the soft tissue registry of the Armed Forces Institute of Pathology. There were 10 males and seven females with a mean age of 53 years (range 24-76 years). Twelve of the 17 cases were large retroperitoneal tumours (mean 170 mm in greatest dimensions). All 17 cases had whorls. Three cases were classified as well-differentiated liposarcoma with whorls and bone formation. Five cases showed coalescing of whorls into areas which may be interpreted as low to intermediate grade dedifferentiation. Five cases had spindled areas associated with the whorls which correlate with classical intermediate to high-grade dedifferentiation. Finally, four cases had a predominant spindle cell component resembling malignant fibrous histiocytoma with focal residual possible sclerosing well-differentiated liposarcoma (scattered adipocytes, adipocytic atypia and/or floret-type giant cells). The meningothelial-like whorls were clustered or scattered throughout the tumours and ranged from 0.09 mm to over 10 mm in diameter in cases with coalescent whorls. Metaplastic bone was present within the whorls or in their immediate vicinity in 10 of 17 cases. Immunohistochemically, the whorl-forming spindle cells showed alpha-smooth muscle actin reactivity in three of seven cases but were negative for epithelial membrane antigen, CD21, and CD35 indicating lack of relationship with meningioma and dendritic reticulum cell sarcoma, other tumours that may contain whorls. Whorls with bone formation revealed cells adjacent to the bone to be positive for osteocalcin, a marker of osteoblastic phenotype. The spindle cells of the whorls were negative for CD34 and CD31, yet these highlighted numerous capillaries inside the whorls in a concentric manner. The whorl-forming cells showed moderate to high MIB-1-index and showed p53 immunoreactivity similar to the dedifferentiated areas but differed from the areas of well-differentiated liposarcoma, which were p53-negative and showed a low MIB-1-index. Follow-up (available in 65% cases) revealed seven patients with metastases or dead of the disease and five patients with one or more recurrences.

CONCLUSIONS

The meningothelial-like whorls represent a mesenchymal proliferation which may undergo pericytic or myofibroblastic, or occasionally osteoblastic, differentiation in liposarcoma. These whorls do not represent dendritic or perineurial/meningothelial differentiation. The significant proliferative activity, p53 reactivity and tendency to coalesce and associate with dedifferentiated liposarcoma suggest that the meningothelial whorls may represent an early sign of dedifferentiation of liposarcoma.

Primary pulmonary meningioma: report of a case and review of the literature

Ten cases of benign primary pulmonary meningioma have been reported in the English literature. We describe herein an additional case of a benign meningioma arising in the lung showing comparable histologic features of sheets and whorls of epithelioid and meningothelial cells with numerous psammoma bodies. Immunohistochemistry showed that the tumor expressed vimentin and epithelial membrane antigen and was negative for keratin, CD34, glial fibrillary acidic protein, CAM 5.2 and S-100, in keeping with previously reported findings. Our review of the literature reveals similar clinical presentations and follow-up behavior and, where reported, similar electron microscopic and immunostaining features.