Esthesioneuroblastoma

Pre and post contrast CT of the brain demonstrates a large frontal mass involving the base of skull and upper nasal cavity. 

Avidly enhancing extra-axial soft tissue mass  with intermediate T1 and T2 signal centered on the right fovea ethmoidalis, cribriform plate and crista galli with extension through the floor of the anterior cranial fossa into the nasal cavity involving the superior and middle nasal turbinates. Small punctate sites of susceptibility artefact at the superolateral aspect of the mass which shows restricted diffusion (ADC values 580 to 700 x 10-6 mm2/s). There is mass-effect on the adjacent brain parenchyma resulting in asymmetry of the anterior horns of the lateral ventricles and left-to-right shift of midline structures measuring 8 mm. Pachymeningeal enhancement is present along the anteroinferior aspect of both cerebral hemispheres and extending along the anterior interhemispheric fissure with leptomeningeal enhancement along the right orbital gyri. The adjacent brain parenchyma demonstrates marked T2 hyperintense signal change within the anterior right frontal lobe traversing the genu of the corpus callosum and involving the left rectus gyri. Intact cortex cannot be discerned between the mass and the white matter, which may represent invasion although this is an unreliable predictor. 

The posterior and middle ethmoidal air cells demonstrate mucosal thickening and right lamina papyracea which abutting the medius rectus muscle. The tumor abuts the right optic canal without direct nerve invasion into the orbital apex. The tumor extends inferiorly involving the frontoethmoidal and sphenoethmoidal recesses with enhancing soft tissue present within the right frontal and right sphenoid sinus.

Conclusion:

Enhancing soft tissue mass centered on the floor of the anterior cranial fossa extending into the nasal cavity and with infiltration of the right frontal lobe. The mass is clearly extra-axial with involvement of the upper nasal cavity. Differential includes A) meningioma, likely high cellularity/mitotic and/or WHO II or III, with brain invasion is a distinct possibility; B) olfactory neuroblastoma - usually more substantial nasal component and peritumoral cysts intracranially. Metastasis, lymphoma and hemangiopericytoma are all less likely differentials. 

MICROSCOPIC DESCRIPTION: The section shows polypoid nasal mucosa in each of the two specimens. The lamin apropria is expanded by a desnely hypercellular tumor. This is a composed of cells with uniform small round and oval hyperchromatic nuclei and minimal cytoplasm. These are arranged in irregularly shaped solid aggregates within a loose fibrous stroma. Frequent mitotic and apoptotic figures are identified. 

Immunohistochemistry shows staining of tumor cells for c-kit, bcl-2, INI-1, BerEp4, CD56 and p16. There is patchy perinuclear dot immunostaining for epithelial membrane antigen (EMA). The following immunostains are negative - MIC2 (CD99), p40, EMA, PgR, TTF-1, chromogranin, neuron specific enolase, pancytokeratin AE1/AE3, synaptophysin, beta-tubulin, CD138, S-100 protein, CD20 and CAM 5.2. There is no light chain restriction.

FINAL DIAGNOSIS: Undifferentiated tumor with features most consistent with esthesioneuroblastoma.