Pilocytic astrocytoma in adults: Histopathological, immunohistochemical and molecular study with clinical association

Pilocytic astrocytoma is the most common primary CNS neoplasm in children and adolescents, rare after the first two decades of life. While some authors report a favorable prognosis in the adult age group with the tumor, others have associated it with higher mortality. The molecular alteration most observed in cases of pilocytic astrocytoma in the pediatric group is the BRAF-KIAA1549 gene fusion, and there are still few studies confirming the presence of this fusion in the adult population. This work investigated genetic alterations involving the 7q34 region in BRAF gene in 21 adult individuals with pilocytic astrocytoma, by FISH. In addition, was identified the immunohistochemical expression of BRAFV600E, correlating these findings with histopathological and clinical ones. BRAF-KIAA1549 fusion appeared in only one case, while in two other cases were found deletions related to the FAM131B-BRAF fusion, suggesting that maybe the latter is more frequently in this population. Through the evaluation of immunoreactivity, 71% of the cases were considered positive and 29% negative. Cases considered positive for BRAFV600E immunoreactivity can potentially be treated through drug therapy with BRAF inhibitors; however, it is always recommended to carry out a molecular study for diagnostic confirmation. This is the first Brazilian study that aimed to investigate possible genetic alterations in the BRAF gene in pilocytic astrocytomas, specifically in adults. Only 1 patient died, but due to operative complications and not the disease itself, suggesting a good evolution of these individuals.

Pathophysiological evaluation of pilocytic astrocytoma in adults: Histopathological and immunohistochemical analysis

Pilocytic astrocytoma is a central nervous system tumor of slow growth, which represents 5 % of all gliomas and most often develops in the cerebellum (42-60 %), but can also arise in other neural areas, such as the optic pathway or hypothalamus (9-30 %); brainstem (9 %); spinal cord (2 %). In the pediatric population, this tumor is the second most common cause of neoplasms and, on the other hand, in adults, it is often rare, probably due to its aggressiveness in these individuals. Studies reveal that the origin of pilocytic astrocytoma is characterized by a fusion between the BRAF gene and the KIAA1549 locus, and the application of the immunohistochemistry technique for the analysis of BRAF protein expression can be a valuable tool for diagnostic purposes. Due to the relative rarity of this disease in adults, there are few publications on the most effective diagnostic and treatment strategies for this tumor. The general objective of this study was to analyze the histopathological and immunohistochemical characteristics of pilocytic astrocytoma in these patients. For this, a retrospective study of patients aged over 17 years with a diagnosis of pilocytic astrocytoma was carried out at the Department of Pathology of UNIFESP/EPM, from 1991 to 2015. In order to define BRAF positivity in the immunohistochemical analysis, at least three consecutive fields with more than 50 % immunostaining were used as criteria and, thus, it was inferred that the 7 cases analyzed were considered positive for the cytoplasmic marker BRAF V600E. Histopathological analysis associated with BRAF immunostaining is of paramount importance as a diagnostic method in these cases. However, future molecular studies will be necessary both for a better understanding of the aggressiveness and prognostic of this tumor and for research involving specific therapies for pilocytic astrocytoma in adults.

Pilocytic Astrocytoma: A Review of General, Clinical, and Molecular Characteristics

Pilocytic astrocytomas are the primary tumors most frequently found in children and adolescents, accounting for approximately 15.6% of all brain tumors and 5.4% of all gliomas. They are mostly found in infratentorial structures such as the cerebellum and in midline cerebral structures such as the optic nerve, hypothalamus, and brain stem. The present study aimed to list the main characteristics about this tumor, to better understand the diagnosis and treatment of these patients, and was conducted on search of the published studies available in NCBI, PubMed, MEDLINE, Scielo, and Google Scholar. It was possible to define the main histologic findings observed in these cases, such as mitoses, necrosis, and Rosenthal fibers. We described the locations usually most affected by tumor development, and this was associated with the most frequent clinical features. The comparison between the molecular diagnostic methods showed great use of fluorescent in situ hybridization, polymerase chain reaction (PCR), and reverse transcriptase-PCR, important techniques for the detection of BRAF V600E mutation and BRAF-KIAA1549 fusion, characteristic molecular alterations in pilocytic astrocytomas.

Necrosis is a consistent factor to recurrence of meningiomas: should it be a stand-alone grading criterion for grade II meningioma?

The purpose of this study was to evaluate spontaneous necrosis as a possible isolated factor for progression and recurrence in grade I meningiomas classified according to the current World Health Organization (WHO) classification. Meningiomas are the most frequently reported primary intracranial tumours, accounting for more than 35%. The 2016 WHO classification of central nervous system tumors stratifies meningiomas in grades I (benign), II (atypical), and III (malignant), according to histopathological aspects and the risk of progression or recurrence. Among 110 patients with intracranial meningiomas, 70 were WHO grade I meningiomas with no findings of atypia (G1WON), 15 were WHO grade I with necrosis (G1WN), 21 were WHO grade II (G2), and 4 were WHO grade III (G3). The mean follow-up was 5.9 ± 0.2 years. High performance scale (KPS ≥ 80) was different (p < 0.001) between WHO grade I meningiomas without (81.4%) and with (60%) necrosis. The 5-year mortality rate was 1.4, 6.7 and 5.9% for G1WON, G1WN and G2, respectively, with significant difference (p = 0.011) related to the presence of necrosis. The risk of recurrence was 3.7 times higher in G1WN than in G1WON (p = 0.017), and 4.2 times in G2 (p = 0.010). Progression-free survival (PFS) was clearly higher in patients with G1WON compared to G1WN and G2 (p = 0.002 and p < 0.001, respectively). There was no significant difference in PFS between G1WN and G2 (p = 0.692). Retreatment was also superior in meningioma with necrosis. Our findings provide clear statistical data to consider that patients with benign meningiomas and histologic findings of spontaneous necrosis are at increased risk of progression and recurrence compared to those with benign lesion without atypical features. Statistical analysis curves also suggest that these lesions behave more similarly to those currently classified as WHO grade II meningioma.

Progressive optic nerve cupping and neural rim decrease in a patient with bilateral autosomal dominant optic nerve colobomas

PURPOSE

To document progressive optic nerve cupping and neural rim decrease in a patient with normal intraocular pressures and bilateral autosomal dominant optic nerve colobomas.

METHODS

The ophthalmology records, stereoscopic fundus photographs, and visual fields of a 27-year-old woman with familial (autosomal dominant) optic nerve colobomas were reviewed. The appearance of the optic nerves was documented over a 13-year period (1985 to 1998).

RESULTS

Despite repeatedly normal intraocular pressures, the patient showed progressive optic nerve cupping and neural rim decrease in both eyes. Visual field testing was available over a 5-year period (1993 to 1998) and was abnormal, but no progression was seen.

CONCLUSIONS

This case of progressive cupping and neural rim decrease in a patient with autosomal dominant optic nerve coloboma in both eyes may provide insight into the optic nerve cupping associated with normal tension glaucoma. Careful follow-up of patients with optic disk colobomas or patients is indicated to detect possible optic nerve changes or field loss.