Isolated Rectal Neurofibroma in the Absence of Neurofibromatosis: Report and Review of Molecular Implications.

Neurofibromas are benign peripheral nerve sheath neoplasms composed of Schwann cells, fibroblasts, perineurial-like cells and axonal elements within a variably collagenous or myxoid stroma. They most commonly arise in the context of neurofibromatosis type 1 (NF1), an autosomal dominant tumour predisposition syndrome driven by inactivating mutations of the NF1 tumour suppressor gene. Isolated colorectal neurofibromas unassociated with syndromic disease are exceptionally rare, and their biological behaviour remains incompletely characterised. We report a case of a 26-year-old man presenting with non-specific abdominal pain who was found to have a solitary rectal submucosal lesion. Endoscopic resection was performed, and histopathologic and immunophenotypic evaluation confirmed the diagnosis of an isolated rectal neurofibroma. This case underscores the diagnostic and management challenges posed by these rare lesions and highlights unresolved questions regarding their molecular underpinnings and malignant potential. LEARNING POINTS: Isolated rectal neurofibromas are extremely rare, particularly without evidence of neurofibromatosis.Gastrointestinal neurofibromas are usually linked to systemic syndromes, especially neurofibromatosis type 1. The lesion can mimic other rectal tumours such as gastrointestinal stromal tumour (GIST), schwannoma or rectal carcinoid tumour.Diagnosis usually requires histopathology and immunohistochemistry.This case highlights the importance of considering rare nerve sheath tumours in the differential diagnosis of rectal lesions.