YO16 - New onset SIADH masquerading progression in esthesioneuroblastoma

Case summary

A 16-year-old female with no known comorbidities presented with nasal blockage, intermittent nasal bleeding, eye pain and headache. There is no family history of malignancies. There was a 2 x 2 cm palpable left level II cervical lymph node. CECT of para-nasal sinuses and CEMRI of orbits showed a large lobulated enhancing mass epicentred in right nasal cavity, with variable extension in right maxillary, ethmoid and sphenoid sinus. There was bony destruction of nasal septum, lateral nasal wall and nasal turbinates. Intracranially extension is seen in basi-frontal region and right side of skull base. Scalloping and erosion of medial wall of right orbit is noted with mass effect on underlying medial rectus muscle and right optic nerve in its intracanalicular and adjacent intracranial part. Biopsy of nasal mass showed features of esthesioneuroblastoma (ENB), Hyams grade II that was immunopositive for chromogranin, INSM1, synaptophysin and focally for NKX2.2 with prominent fibrovascular stroma. However, rosettes, calcification and necrosis was absent. Patient was started on palliative chemotherapy with cisplatin and capecitabine. Subjective and radiological response was present after three cycles with enhancing lesion present in posterior aspect of right nasal cavity extending to bilateral sphenoid sinus and erosion of sinus.

However, after receiving 5 cycles patient developed recurrent episodes of hyponatremia and an episode of generalised seizures. Blood and urine investigations showed - Hb - 12.0g/dL, TLC - 8700/mm3, Platelet - 314x103/mm3, Blood urea- 14mg/dL, serum(S) creatinine-0.7mg/dL, Total bilirubin-0.7mg/dL, S. AST-26U/L, S. ALT-13U/L, S. ALP-97U/L, S. Sodium-106mmol/L, S. Potassium-3.9mmol/L; Urine potassium - 16.06mmoL/L, Urine sodium-121mmol/L, Urine osmolality- 382mosmkg/water.

CEMRI of orbit and PNS was done which showed progressive disease with the mass in nasopharyngeal wall extending into sella region causing erosion of sella and clivus. It was also extending into cavernous sinus, middle cranial fossa and causing erosion of bilateral medial temporal bones and encasing bilateral extraorbital optic nerves. Clinical findings are suggestive of new onset paraneoplastic SIADH associated with progressive ENB.

Clinical trial identification

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