A Patient with an Ileocecal MiNEN and a SynchronousSquamous Non-Small-Cell Lung Cancer: Case Report andReview of the Literature

Mixed neuroendocrine non-neuroendocrine neoplasms (MiNENs) are rare tumors composed of two different histologicalcomponents, one of which is of a neuroendocrine origin. Given its suggested underdiagnosis and consequent low prevalence, noclear diagnostic and treatment guidelines are available, and treatment usually follows regimens similar to that of the mostaggressive component. On the other hand, multiple primary tumors (MPTs) are also rare neoplastic entities that usually confera challenge regarding treatment options, for a regimen that comprises both the primary and the synchronous/metachronousmalignancy should be used. Here, we discuss the challenging diagnostic and therapeutic management of a patient with anileocecal MiNEN that presented along with a synchronous squamous non-small-cell lung cancer (SQ-NSCLC). The patientpresented with intestinal obstruction symptoms for which he underwent an emergency resection of the ileocecal MiNEN. Aninitial CT scan showed an additional lung mass later identified as an SQ-NSCLC after bronchoscopy biopsy analysis. Given therapid hepatic metastatic progression, palliative platinum-based chemotherapy was initiated, with an adequate response of thelocal and metastatic lesions of the MiNEN, but suggested platinum resistance and progression of the pulmonary neoplasm.Second-line treatment with pembrolizumab directed for the SQ-NSCLC was initiated; however, it was stopped after immune-mediated toxicities developed. A third-line chemotherapy scheme with carboplatin/gemcitabine was initiated, but centralnervous system (CNS) progression developed, with the patient dying 11 months after initial diagnosis