Isolated parenchymal cysts associated with a secretory meningioma: illustrative case

Abstract

BACKGROUND

Meningiomas represent one of the most common intracranial tumors found in adults. Uncommonly, these tumors can be associated with an adjacent cyst, which is in direct contact with the tumor. Tumor location and source have previously been categorized into five subtypes.

OBSERVATIONS

This report details the novel findings of a secretory meningioma with associated cysts separated from the tumor by brain parenchyma. Histopathological analysis of the cyst wall showed no evidence of neoplasia, suggesting the etiology to be from the parenchymal edema.

LESSONS

The authors suggest that the presence of isolated cysts in conjunction with a meningioma (in this case a secretory meningioma) represents a new type VI cyst. These cysts are nonneoplastic and do not require direct operative access for control but can be managed, if needed, with simple aspiration.

https://thejns.org/doi/10.3171/CASE25964

Meningiomas represent one of the most common tumors found in adults. Uncommonly, these tumors can be associated with an adjacent cyst that is in direct contact with the tumor. This report details the finding of a meningioma with associated cysts separated from the tumor, but thought to be related to the peritumoral edema. The imaging, histopathology, classification, and therapeutic management of this unique finding are discussed.

Illustrative Case

A 66-year-old female presented for evaluation after several months of intermittent staring spells and dysphasia. These episodes occurred one to two times per week and typically lasted several minutes per event. She possessed no history of neurological or contributory medical conditions and was diagnosed with seizures and appropriately placed on antiseizure medications and steroids.

MRI was performed and revealed several findings. The patient was found to harbor a large homogeneously enhancing extra-axial mass along the left medial middle fossa, appearing to be contiguous with the cavernous sinus (Figs. 1 and 2). An extensive amount of edema was noted within the temporal lobe (Fig. 3). Because of the mass and edema, a midline shift of 8–10 mm was present. Additionally, within the edematous parenchyma, two cysts were noted in the superior and middle temporal lobes. Both of these cysts measured approximately 15–20 mm and were clearly separated from one another and the extra-axial mass by brain parenchyma (Figs. 1 and 2). The superior gyrus cyst was located well anterior to the expected region of Wernicke’s area and remained inferior to the sylvian fissure and the opercular region. The middle temporal cyst, while located more posteriorly, still remained within 4 cm of the temporal pole. Based on these characteristics, we deferred preoperative functional MRI (fMRI) and an awake craniotomy, relying instead on anatomical features to avoid speech center injury.

FIG. 1.

Preoperative coronal T1-weighted postcontrast MR image demonstrating a left cavernous meningioma and inferior cyst (arrow), which is notable for the lack of contrast enhancement and separation from the tumor.

FIG. 2.

Preoperative coronal T1-weighted postcontrast image demonstrating a superior cyst (arrow) similarly without contrast enhancement and located distant from the tumor.

FIG. 3.

Preoperative axial T2-weighted MR images illustrating an inferior cyst (white arrow), superior cyst (black arrow), and surrounding vasogenic edema.

At the time of outpatient evaluation, the patient was without any abnormal findings on neurological examination. Since starting antiseizure medication, the staring spells and dysphasia had resolved. It was recommended to the patient that she proceed to surgery in an expedited fashion.

Operative Details

The patient was positioned supine with the head turned approximately 60° contralateral to the affected side, and surface anatomy was registered for intraoperative navigation. A pterional incision was marked from the posterior root of the zygoma extending superiorly toward the midline. An interfascial dissection of the temporalis was performed to increase inferior temporal exposure. A standard pterional craniotomy was performed with additional drilling along the sphenoid wing to improve inferior access.

A wide dural opening was made to allow for swelling of the underlying brain. Immediately after the dural opening, intraoperative ultrasound was used to verify the location of the cysts. The superior gyrus cyst was located well anterior to the expected region of Wernicke’s area and remained inferior to the sylvian fissure and the opercular region. The middle temporal cyst, while located more posteriorly, still remained within 4 cm of the temporal pole. Based on these characteristics, we deferred preoperative fMRI and/or an awake craniotomy, relying instead on anatomical features to avoid speech center injury. Navigation confirmed cortical entry points away from potential speech centers. A small cortical incision was made over the superior cyst, clear fluid was suctioned, and a cottonoid was placed within the cyst. The second cyst was then accessed in a similar manner. After decompression of both cysts, the brain relaxed, allowing for further exploration. Under the operating microscope, the cyst walls were inspected and did not appear to harbor any abnormal tissue. Multiple biopsies were obtained from both cyst walls.

After decompression and biopsy of the cysts, the inferior temporal lobe was gently elevated with a single retractor. Because of the continued edema, several millimeters of the inferior temporal gyrus were resected to facilitate access to the tumor. The tumor was immediately identified and appeared clearly extra-axial with moderate vascularity. Specimens were obtained as resection proceeded and intraoperative pathology returned as “secretory meningioma.” Ultrasonic aspiration continued to remove the tumor up to the border of the lateral cavernous sinus. Based on a preoperative discussion with the patient, it was decided not to perform an intracavernous resection of the tumor due to the patient’s desire to avoid ophthalmoplegia.

The patient tolerated the procedure well with no new deficits other than mild facial numbness. Six-month postoperative imaging revealed collapsed cysts, resection of the extra-cavernous tumor, and greatly reduced vasogenic edema, which contributed to lessened mass effect in the region (Fig. 4).

FIG. 4.

Six-month postoperative coronal T1-weighted postcontrast image demonstrating marked reduction in vasogenic edema and mass effect, as well as decompressed cysts (arrows) and residual cavernous tumor.

Histopathological Analysis

Histopathological examination of the mass showed a meningothelial neoplasm with a vague lobular pattern. The tumor cells exhibited multifocal epithelial differentiation and contained many round extracellular eosinophilic secretions (pseudopsammoma bodies) (Fig. 5A and B). Mitotic activity was low, with less than 1 per 10 high power fields. No brain invasion or tumor necrosis was seen. Immunohistochemically, the tumor cells showed focal positivity for progesterone receptor (Fig. 5C). Of note, the eosinophilic secretions were positive for periodic acid-Schiff and carcinoembryonic antigen (Fig. 5D and E) and are surrounded by tumor cells with epithelial differentiation, highlighted by pan-cytokeratin staining (Fig. 5F). Overall, the pathology diagnosis was secretory meningioma, CNS WHO grade 1.

FIG. 5.

The tumor cells show a vague lobular architecture with numerous round extracellular eosinophilic secretions (A and B). Progesterone receptor (PR) is focally positive in the meningioma tumor cells (C), while the eosinophilic secretions are positive for periodic acid-Schiff (D) and carcinoembryonic antigen (CEA) (E). Surrounding meningothelial cells exhibit pan-cytokeratin positivity, consistent with epithelial differentiation (F). Biopsy specimens from the cystic region show edematous reactive brain parenchyma with many Rosenthal fibers (G and inset), and the gliotic tissue is highlighted by glial fibrillary acidic protein (GFAP) immunostaining (H).

Histological examination of the cystic lesions revealed edematous reactive brain parenchyma with a few scattered inflammatory cells. There were Rosenthal fibers in the gliotic regions (Fig. 5G and H). No meningioma tumor cells were identified.

Informed Consent

The necessary informed consent was obtained in this study.

Discussion

The WHO classifies meningiomas into three grades: grade 1 tumors are benign, typically slow-growing, and account for 80%–90% of cases.¹ Grade 2 tumors demonstrate atypical features characterized by accelerated growth and recurrence rates, while grade 3 tumors are malignant and aggressive.² Together, grades 2 and 3 represent approximately 20% of reported meningiomas.³ Benign meningiomas comprise about 37% of all reported CNS tumors and nearly 50% of all intracranial tumors,^4,5 making them the most common type of benign brain tumor.^1,3,4,6–8 Most meningiomas arise from arachnoid cap cells within the arachnoid mater.⁴ Their pathogenesis is thought to result primarily from abnormal cell proliferation driven by genetic alterations.⁴ Secretory meningiomas most commonly derive from mutations in the TRAF7 and KLF4 genes.^7,8 One study analyzed 30 secretory meningiomas, finding identical K409Q mutations in the KLF4 gene along with mutations in the TRAF7 gene in 29 of the 30 analyzed tumors.⁸ KLF4 mutations were found to be unique to secretory meningiomas, whereas mutations in the TRAF7 gene, typically located within the WD40 domain, were found in meningothelial and atypical meningiomas as well.^8,9

Observations

While meningiomas themselves are common, a related cyst represents an unusual finding. In approximately 2%–7% of reported cases,^8,10 cysts may form either within a meningioma (intratumoral) or adjacent to the tumor (peritumoral).¹⁰ Such cysts can contribute to additional pressure on surrounding brain structures, depending on their size and location.

Five distinct cyst types associated with meningiomas have been described. Type I cysts are intratumoral, with the tumor macroscopically enclosing the cyst. Type II cysts are also intratumoral but located at the tumor margin, microscopically surrounded by a rim of neoplastic cells. Type III cysts are peritumoral, with walls composed partly of adjacent brain parenchyma and partly of tumor tissue. Type IV cysts are peritumoral, with walls formed by the arachnoid and separated from the tumor by a distinct capsule. Type V cysts are characterized by entrapped CSF.¹¹ Although peritumoral cysts are located outside the meningioma tumor mass, they are found in direct contact with the tumor.¹¹

In this case, however, the cysts were clearly isolated from the actual tumor (Figs. 1 and 2), although they did reside within the edematous affected temporal lobe. Histopathological evaluation confirmed a secretory meningioma subtype, which constitutes approximately 1.1%–3.0% of all meningiomas.⁵ Additionally, secretory meningiomas typically demonstrate significant peritumoral edema, often disproportionate to the tumor size.⁶ Given the meningioma subtype⁷ and the lack of neoplastic cells within the cyst walls, the authors postulate that the cyst formation was secondary to the associated peritumoral edema but did not represent extension of neoplasia.

To the authors’ knowledge, this case represents a novel presentation of parenchymal cysts associated with but not in contact with a neighboring secretory meningioma. We offer this as a type VI meningioma-related cyst.

Lessons

Based on these findings, it is suggested that decompression or resection of any cyst separated from a meningioma is not mandatory for management as the cyst would likely recede after tumor resection and resolution of the associated edema. If, as in this case, cyst reduction would relax the brain and thereby aid in the access and resection of the tumor, then simple decompression could be performed with a needle or catheter. Visual access of the cyst wall is not required. Furthermore, a remote cyst within edematous brain would also suggest to the surgeon the possible presence of a secretory meningioma.

Disclosures

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author Contributions

Conception and design: NE Simmons, BT Simmons. Acquisition of data: NE Simmons. Analysis and interpretation of data: all authors. Drafting the article: all authors. Critically revising the article: NE Simmons, BT Simmons. Reviewed submitted version of manuscript: NE Simmons, BT Simmons. Approved the final version of the manuscript on behalf of all authors: NE Simmons. Study supervision: NE Simmons.

Correspondence

Nathan E. Simmons: Dartmouth Health, Lebanon, NH. nathan.e.simmons@hitchcock.org.