A Case Report of Mandibular Gingival Metastasis From Sigmoid Colon Adenocarcinoma With Phenotypical Transformation Into Neuroendocrine Carcinoma

This case report presents a 59-year-old female patient with mandibular gingival metastasis from adenocarcinoma of the sigmoid part of the colon, who underwent radical colectomy with simultaneous hysterectomy involving and left oophorectomy (due to tumor involvement) eight years ago. Because of metastatic spread to the liver, a partial left lateral lobectomy was performed, and because of a metastatic lesion in the left adrenal gland, the latter was excised and a partial resection of the left kidney was performed. The patient was given a number of courses of chemotherapy, target therapy, and immunotherapy. In 2024, because of a tumor mass in the oral cavity that was growing and interfering with normal nutrition and speech, she was hospitalized and a radical resection of the lesion was performed along with the involved underlying bone of the lower jaw on the right. The morphological analysis revealed metastasis from large cell neuroendocrine carcinoma and the immunohistochemical stains verified the gastrointestinal origin of the lesion. The lesion was accepted as being a result of the phenotypical transformation of the primary adenocarcinoma of the sigmoid colon. The patient had a normal postoperative period and a smoothly healing wound and continued to be under the management of clinical oncologists supporting chemo-, targeted, and immunotherapy. However, five months after the appearance of the lesion and three months after its surgical removal, after a serious deterioration of her general condition, she passed away at home.