A 26-y-old, male, captive Humboldt penguin (Spheniscus humboldti) was euthanized following a 3.5-mo history of weakened elimination mechanics, recurrent tenesmus, intermittent hemorrhagic droppings, and a cloacal mass. Blepharospasm, of unknown cause, of the right eye was present for ~3 mo before euthanasia. Autopsy revealed a cloacal adenocarcinoma with localized coelomic carcinomatosis and distant metastases to the liver and lungs. On histopathology, a 2.6 × 1.2 × 0.5-mm, well-demarcated mass was found surrounding the right optic nerve, expanding the subdural space and wrapping the leptomeninges. The mass was composed of neoplastic spindle-to-polygonal cells consistent with a meningioma, meningothelial subtype. No evidence of neoplasia was found in the optic chiasm or brain, indicating a primary retrobulbar meningioma. Immunohistochemistry for cytokeratin AE1/AE3, vimentin, and S100 revealed robust and consistent immunoreactivity to vimentin, and weak and variable immunoreactivity to cytokeratin and S100, supporting the diagnosis. Meningiomas have been described only rarely in avian species, and we found no reports of optic nerve meningiomas in any avian species to date. The optic nerve meningioma in this case was considered a clinically incidental finding.

Meningiomas represent one of the commonest benign neural tissue neoplasms, but it is an extremely rare finding in the oral cavity. It tends to arise from the arachnoid cap cells pertaining to dura matter of the Meninges, the choroid plexus, or the brain stem. Herein, we report the case of a 36-year-old male patient, who visited our Department with the chief complaint of facial swelling associated with asymmetry. Based on thorough clinical, radiological, histopathological and immunohistochemical analyses, a diagnosis of Primary Extracranial Meningioma (PEM) of the Maxilla was made. Later, the tumor was surgically removed, and on follow up, the patient is doing well. Our presented case is extremely unique-it represents a PEM involving the oral cavity.

UNASSIGNED: The origin of meningioma tumors is known as the meningothelial or arachnoid cap cells. The arachnoid granulations or villi are concentrated along with the dural venous sinuses in the cerebral convexity, parasagittally, and sphenoid wing regions. The majority of meningiomas are found in these locations with dural attachment. Infrequently, meningiomas develop without dural attachment but in dural adjacent. There are numerous reports of patients with cranial nerve involvement as a result of the compressive effect of the sinus cavernous or adjacent structures meningioma tumor on the cranial nerve.
UNASSIGNED: In this study, we reviewed all reports of patients with third nerve involvement as a result of meningioma tumors in addition to the introduction of a new case. We present a 47-year-old woman presented with headache, diplopia, and ptosis. A gadolinium-enhanced mass on anterolateral of the left cerebral peduncle with no dural attachment was suggesting for Schwannoma at preoperative imaging. An adhesive 10 × 5 × 4 mm meningothelial meningioma arising from the oculomotor nerve was resected.
UNASSIGNED: The findings of this review suggest that there may be other mechanisms as the origin of meningiomas tumors. It is crucial to take into account origination mechanisms of meningioma using ectopic meningiomas due to the increasing prevalence of meningioma.

Meningiomas are a diverse group of neoplasms that exhibit a wide range of morphologies and clinical behavior. They are generally accepted to originate from arachnoid cap cells within the leptomeninges. Classic histologic features include whorl formations, psammoma bodies, nuclear holes, and nuclear pseudoinclusions. Meningiomas are classified as benign, atypical, or anaplastic (grades I, II, or III) based on histologic features including mitotic activity, brain invasion, and presence of other minor criteria. There are numerous histologic variants of meningiomas, and some are associated with worse clinical outcomes and therefore are assigned a higher grade. The majority of meningiomas show diffuse positivity for vimentin and epithelial membrane antigen, supporting the dual mesenchymal and epithelial nature of meningothelial cells. The presence of an elevated proliferation index (as measured by Ki-67 immunohistochemical stain) and loss of progesterone receptor expression are associated with the higher grade. Pathologic features including histologic variants, grading criteria, and ancillary tests such as special and immunohistochemical stains are discussed.

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.

Hemorrhage associated with meningiomas is extremely rare and most commonly occurs in convexity meningiomas of higher grade or the angioblastic variety. Moreover, bleeding associated with a meningioma usually occurs in the form of a subdural hematoma or subarachnoid hemorrhage. We report a case of giant left medial sphenoid wing meningioma with histopathological diagnosis of a meningothelial type with apoplexy. A 54-year-old female presented with clinical features suggestive of apoplexy. Her neuroimaging demonstrated a large left medial sphenoid wing meningioma with features suggestive of an intratumoral bleed with mass effect. Gross total excision of the tumor was done with the good postoperative outcome. The biopsy came out to be Grade I meningothelial meningioma. Apoplexy in meningiomas is extremely rare with a reported incidence of 0.5%-2.4%, especially in a nonconvexity meningioma with histopathological diagnosis of meningothelial variety. Early diagnosis and prompt surgical intervention are critical as meningiomas associated with apoplexy are associated with high morbidity.

Choristomas and hamartomas within the oral cavity are relatively uncommon lesions and may present with diverse clinical and histopathological appearances. In this report, we describe two infant patients with hamartoma with ectopic meningothelial elements involving tongue and maxillary alveolar ridge. To the best of our knowledge, these are the first two cases in which a meningothelial proliferation has been identified in the oral cavity. Hamartoma with ectopic meningothelial elements is a rare condition that has been classically described occurring in the scalp. These lesions are characterized by bland round to spindle-shape cells that interdigitate through collagen bundles and express progesterone receptor and epithelial membrane antigen by immunohistochemistry supporting a meningothelial origin.

OBJECTIVE: MUC4 is a transmembrane glycoprotein that plays a role in cell growth signalling and is expressed in various epithelial tissues. Gene expression profiling and immunohistochemical analyses revealed that MUC4 is also constantly and specifically expressed in low-grade fibromyxoid sarcomas and sclerosing epithelioid fibrosarcomas among the mesenchymal tumours, and immunohistochemical detection of MUC4 is extremely useful for their diagnoses. In our routine pathological practice, we noticed that meningiomas are also often positive for MUC4, which has not yet been reported previously, despite the extensive scrutiny of its expression in soft tissue tumours.
RESULTS: We examined immunohistochemically the expression of MUC4, progesterone receptor (PgR) and somatostatin receptor 2A (SSTR2A) in 140 meningiomas of various histological subtypes and 123 other mesenchymal tumours, including intracranial or sinonasal tumours and peripheral nerve sheath tumours. MUC4 was expressed in 130 meningiomas (92.9%). MUC4 expression was constant and almost diffuse in meningothelial and angiomatous subtypes, whereas it was limited in 5% or fewer tumour cells or absent in 26 of 28 fibrous meningiomas. All other mesenchymal tumours examined were negative for MUC4. PgR and SSTR2A were expressed in 94 (67.1%) and 134 (95.7%) meningiomas, respectively. Five of six SSTR2A-negative meningiomas focally expressed MUC4.
CONCLUSIONS: MUC4 is expressed variably but almost consistently in meningiomas, particularly in meningothelial or angiomatous subtypes. Its immunohistochemical detection is useful to distinguish meningiomas from other intracranial or head and neck mesenchymal tumours, particularly those with epithelioid features. Our study could expand a variety of MUC4-positive mesenchymal tumours.

Ectopic meningothelial proliferations are rare and can occur in a multitude of extracranial/spinal anatomic locations. Perineurioma is another uncommon entity that shares similar histological characteristics to those found in meningothelial proliferations. These include bland spindle cells with thin, bipolar nuclei; eosinophilic cytoplasm; and indistinct cell borders, arranged in short fascicles with whorl formation. Given their uncommon occurrence and shared histological and immunohistochemical features, their distinction can present a diagnostic challenge. Immunohistochemical studies can provide guidance when attempting to distinguish between these 2 lesions. Here, we present an unusual case of a patient with Cowden syndrome who was discovered to have a meningothelial proliferation within an axillary lymph node. To the best of our knowledge, this is the first case in which a meningothelial proliferation has been identified in a lymph node. Furthermore, the occurrence in a patient with Cowden syndrome is intriguing and raises the possibility of a pathogenetic link.