Aggressive pituitary adenoma in the context of Lynch syndrome: a case report and literature review on this rare coincidence.

Purpose: Lynch Syndrome (LS) is a cancer-predisposing condition resulting from hereditary mutation of DNA mismatch repair genes. Gastrointestinal, urogenital, and endometrial carcinomas are well-known to predominantly occur in LS patients. In contrast, there are only few reports on brain tumours in the context of LS and to date intracranial tumour manifestation appear to be rather coincidental.

Methods: We present the case of a 56-year-old female developing aggressive lactotroph pituitary adenoma following a history of multiple Lynch-associated malignomas and having a confirmed MSH2 mutation. Furthermore, we performed a literature review via PubMed using the search terms 'Lynch Syndrome', 'HNPCC', 'MMR mutation' combined with 'intracranial tumour', 'sellar tumour', 'pituitary adenoma', or 'pituitary carcinoma', focusing on other reported cases and treatment regimens.

Results: A handful of studies have indicated an increased frequency of brain tumours in the context of LS, predominantly glioblastoma and less frequently low-grade glioma or other brain tumours. Based on our literature review, we summarized the known instances of pituitary adenoma in LS patients, including the present case. Furthermore, we reviewed the common recommendation of using temozolomide (TMZ) for treatment of aggressive pituitary adenoma or carcinoma and found strong indication that it might be insufficient in LS patients, while PD-1 blockade could be a promising treatment option.

Conclusions: Combined with our case, there is a growing body of evidence that intracranial tumours and in particular those of the sellar region might be more prevalent in LS patients than previously assumed, due to their genetic profile substantially affecting viability and efficacy of treatment options. Clinical signs of aggressive tumour growth in combination with irresponsiveness to standard treatment in case of recurrence should lead to further diagnostic measures, because revelation of germline MMR mutations would call for an extended screening for other neoplastic manifestations and would markedly influence further treatment.