Subependymal giant cell astrocytoma: Cytological findings.

Sir,

Subependymal giant cell astrocytoma (SEGA) is a benign, slowly growing tumor typically occurring in the setting of tuberous sclerosis complex (TSC) with long-term survival. It usually arises from the medial portion of the lateral ventricle, grows into the lateral ventricle and may obstruct the foramen of Monro. Increased intracranial pressure, unaccompanied by focal neurological deficit is the most frequently observed clinical symptom. According to revised WHO classification of CNS tumors, SEGAs were included in the group of low astrocytic neoplasms.[1-3]

In this report, we describe the cytological finding of a case of SEGA. A 23-year-old female, a known case of TSC from childhood presented with headache, vomiting and evidence of elevated intracranial pressure.

Computed tomography (CT) scan showed a mass at the foramen monro with dilatation of left lateral ventricle as well as subependymal nodule or candle guttering associated with TSC. Imprint intraoperative cytology revealed hypercellular smears composed of loosely cohesive clusters of cells in variable size and shapes. The large cells had round to oval nuclei with minimal atypia, fine, evenly distributed chromatin; and abundant eosinophilic cytoplasm. The individual cells had abundant thin, hair-like processes. Few spindled astrocytic cells were also identified. The chromatin was evenly distributed. The cytoplasm was abundant eosinophilic and varied in texture from finely granular to fibrillary. Nuclear cytoplasmic inclusion was found. Neither mitotic figure nor necrosis was observed [Figure 1].

Figure 1

Cytology: Cluster of cells with slight nuclear atypia and nuclear cytoplasmic inclusion, Inset: Section shows large cells with abundant eosinophilic cytoplasm, eccentric nuclei with slight atypia (H and E, ×100)

Brain tumors particularly those containing giant cells or large neurons such as gemistiocytic astrocytoma (GA), glioblastoma multiformis (GBM) and ependymoma, due to its location, should be considered in differential diagnosis.[3-5]

In GA and GBM, the cells have numerous hair-like processes and cohesive clusters of tumor cells are absent. Nuclear atypia, hyperchromasia, and mitosis are easily seen. Although rosettes and rosette-like structures may be observed in both tumors, the cells of ependymoma are smaller, with very scant cytoplasm.[1-4]

In histological sections, our case was composed of three main kinds of cells, swollen gemistocytic-like cells, fibrillated spindle cells and giant pyramidal cells with a ganglioid appearance [Figure 1, Inset].

Immunophenotypically, there is evidence for dual neuronal and astrocytic differentiation. Reactivity for glial fibrillary astrocytic protein, S-100, neuron-specific enolase and synaptophysin expression are seen. Ki-67 (MIB-1) labeling index is very low (<1%).[5]

Electron microscopic studies have confirmed both the astrocytic and neuronal nature of these neoplasms. The tumoral cells demonstrate intermediate filaments, electron dense core vesicles and even synaptic structures in individual cells.[5] The mixed ultrastructural and immunophenotypic character of SEGAs suggests that the tumor is composed of progenitor cells capable of divergent differentiation.[145]

In conclusion, the cytological features of SEGA are very helpful for exclusion of the mimics. However, it is emphasized that clinicopathological and radiological information is critical for final diagnosis.