New developments in the pathology of skull base tumors

Abstract

As an anatomical interface between various tissues, the skull base harbors an exceptionally broad variety of neoplasms, some of which pose a major challenge for surgical pathology. The characterization of distinct immunohistochemical expression profiles and the identification of molecular genetic alterations associated with different tumor entities have significantly advanced this field. The new World Health Organization (WHO) classification of tumors of the nervous system lists 15 histopathological variants of meningioma. Of clinical importance are those entities that carry an increased risk of recurrence and a poor prognosis, i.e., the atypical meningioma (WHO grade II), clear-cell meningioma (WHO grade II), chordoid meningioma (WHO grade II), rhabdoid meningioma (WHO grade III), papillary meningioma (WHO grade III), and anaplastic meningioma (WHO grade III). Diagnostic criteria for atypical and anaplastic meningioma variants have now been stringently defined. The differential diagnosis of meningiomas includes hemangiopericytoma, hemangioblastoma, solitary fibrous tumor, sarcomas, and chordoid neoplasms. Recent data highlight the importance of distinguishing chordoma and chondrosarcoma of the skull base since chondrosarcomas show a significantly better clinical outcome. Among the less common, aggressive tumor entities in this anatomical region, infiltrating pituitary adenoma/pituitary carcinoma, superficial malignant gliomas, rhabdomyosarcoma, olfactory neuroblastoma, various sarcomas, and malignant lymphoma must be considered. Profiles of molecular genetic alterations have been established for several of these neoplasms and may facilitate the differential diagnosis. This review summarizes recent developments in the histopathological characterization, classification, and molecular pathology of neoplasms arising at the skull base.

Malignant Transformation of Clival Chordoma After Gamma Knife Surgery -Case Report-

“…18,23) However, the present tumor was positive for EMA and cytokeratin, and faintly positive for vimentin and S-100 protein, which demonstrated the epithelial nature. Several theories have been proposed to explain sarcomatous change, including arising adjacent to irradiated chordoma, arising from the Neurol Med Chir (Tokyo) 47, October, 2007…”

Chordoid Meningioma: A Case Report

“…Chordoid glioma is strongly glial fibrillary acidic protein-positive (12). Microcystic variant of meningioma shows considerable overlap with some features of chordoid meningioma, because it may display certain degrees of myxoid stromal changes and cytoplasmic vacuolation (11,14). However, this variant lacks inflammatory cell infiltrates.…”

“…Lymphoplasmacyte-rich meningiomas do not exhibit chordoid features (15). In clinical aspect, the chordoid meningioma corresponds to WHO grade II (atypical meningioma) because of its more aggressive clinical behavior, and is recommended to be followed up at regular intervals after surgery (10,11).…”

“…In addition, the presence of histologic and immunohistochemical features of a classical meningioma, i.e., whorl formation and immunohistochemical staining for vimentin and epithelial membrane antigen in the absence of prominent cytokeratin expression, facilitates the differential diagnosis (6,11). The differential diagnosis of chordoid meningioma includes chondroid chordoma, myxoid chondrosarcoma, chordoid glioma and other variants of meningiomas (4,6,(11)(12)(13)(14). Chordomas usually locate in the midline and show strong widespread staining for cytokeratin and epithelial membrane antigen (4).…”

A retrospective study of skull base neoplasia in 42 dogs

“…These results are similar to what has been reported in the adult human population, where the most common skull base neoplasms are meningiomas, pituitary adenomas, vestibular nerve sheath tumors, and craniopharyngiomas, followed by chordomas, chondrosarcomas, chemodectomas, and olfactory neuroblastomas. 27 Canine meningiomas occur more frequently in the brain and less frequently in the spinal cord. 22 Common locations in the brain include the frontal or basal telencephalic areas and less often the sellar area, 25,34,35 cerebellopontine angle, 10,14,35 retrobulbar spaces, 25,26,40 and middle ear.…”