Introduction: Neuroendocrine tumours (NETs) may change grade and clinical behaviour substantially over time, requiring shifts in management strategy.
Case Presentation: A 53-year-old lady presented with abdominal bloating and diarrhoea. Diagnostic MRCP and CT-CAP confirmed metastatic cancer, with bilobar liver metastases and a sclerotic lesion in the right ilium. Her disease was 68Ga-DOTATATE-avid. Rectal biopsy confirmed a grade 1 rectal primary lesion (Ki67 index 2%). Liver biopsy revealed a grade 2 well-differentiated NET (Ki67 index 5%). She initiated lanreotide therapy but progressed after 6 months in both the liver and mesorectal lymph nodes. Subsequently, she was switched to capecitabine-temozolamide but progressed after 3 cycles. She was converted to second-line peptide receptor radionucleotide therapy (PRRT), achieving stable disease for approximately two years. She subsequently developed abdominal pain and was found to have marked progression in the liver. She was admitted for repeat liver biopsy and transarterial embolization of her symptomatic metastases. New histology showed a grade 3 tumour (Ki67 index 41%). She was therefore switched to chemotherapy-based strategy with FOLFOX. Molecular studies on the new tissue unfortunately revealed no actionable mutations.
Conclusion: NETs may change grade during treatment. In such cases, repeat biopsy and further molecular analyses can inform alternate treatment approaches.