Anaplastic astrocytomas with abundant Rosenthal fibers in elderly patients: A diagnostic pitfall of high‐grade gliomas

Abstract

To investigate the clinicopathological features of anaplastic astrocytoma (AA) with abundant Rosenthal fibers (RFs), this study assessed four cases of AA (elderly patients; age ≥ 70 years). Histologically, these tumors were composed of diffusely infiltrating astrocytomas with brightly eosinophilic cytoplasmic granules or cork-screw or beaded bundles. Tumor cells showed pleomorphism, bizarre giant cells, and mitotic activity, but no necrosis. The cytoplasmic granules showed negativity on PAS staining. Immunohistochemically, the tumor cells with cytoplasmic granular cells showed a positive reaction for GFAP. The cytoplasmic eosinophilic granules or bundles were positive for αB-crystallin, ubiquitin and HSP27. In addition, tumor cells showed strong cytoplasmic positivity for isocitrate dehydrogenase 1 (IDH1)-R132H protein in all cases. The MIB-l labeling index of these cases ranged from 7% to 10%. In cases 1 and 2, ultrastructurally, the tumor cells had electron-dense, amorphous structures in the cytoplasm and in the processes. These structures were bound to glial intermediate filaments. Based on these microscopic, immunohistochemical and ultrastructural findings, case 1 was diagnosed as AA with abundant, mixed, common type of RFs and miniature (m) RFs, and cases 2,3, and 4 were diagnosed as AA with abundant mRFs. These results indicate that the presence of RFs in astrocytic tumors does not necessarily exclude a diagnosis of high-grade astrocytoma. In addition, AAs with abundant mRFs in elderly patients should be classified as a peculiar variant of AA.

Adult anaplastic pilocytic astrocytoma – a diagnostic challenge? A case series and literature review

“…Moreover, a recent series reporting 3 cases of adult APA, including 2 patients with NF-1, further emphasized the association of this phakomatosis with APA [9]. However, whether screening for NF-1 in patients diagnosed with APA should be performed as part of the standard clinical workup merits further investigation; in our case series as well as in others a minority of patients had NF-1 [1,3].…”

“…Sugita et al describe a strong positive staining pattern for IDH1-R132H protein in anaplastic astrocytoma with abundant Rosenthal fibers [3]. However, our cases were all negative for IDH1-R132H staining.…”

“…While KIAA1549/BRAF fusion products are highly specific for pilocytic astrocytoma, they are only found in small fractions of supratentorial and adult pilocytic astrocytomas [19]. Conversely, the presence of an IDH1 mutation links rare tumors that could morphologically be regarded as APA with the group of diffusely infiltrating gliomas, although its absence does not rule out a conventional high-grade astrocytoma [3].…”

“…However, the clinical course of APA is perceived to be more favorable as compared to conventional anaplastic astrocytomas [3,4]. Here, we present 3 new cases with APA in adults diagnosed at our institution over the last decade and provide a first review of the current clinical, histopathological, and neuroradiological literature to update the reader's knowledge about APA.…”

“…Anaplastic astrocytoma frequently progresses to secondary glioblastoma after a mean interval of 2 years [3]. However, Sugita et al describe 2 cases (out of four) of anaplastic astrocytoma with abundant Rosenthal fibers that followed a more indolent course than conventional anaplastic astrocytoma [3].…”