Symptoms such as those listed above often prompt a medical evaluation leading to the diagnosis. Sometimes, routine gynecologic pelvic exam may reveal a cervical mass. Biopsy should be performed of any cervical mass to determine a more definitive diagnosis. Occasionally, early disease may be detected by routine screening Pap smear. Although Pap smear may detect the disease, the efficacy of it as a screening modality is unknown, and it likely performs worse than it does for other cervical cancers. Some women with NEC of the cervix have had normal annual Pap smears leading up to the time they were diagnosed with cancer.

As mentioned above, more advanced disease may be associated with different symptoms leading to different routes of diagnosis. Ultimately, biopsy of a tumor in the cervix or other metastatic tumor will be obtained and analyzed by a pathologist. Under the microscope, neuroendocrine cancers of the cervix appear identical to those originating in the lung. Special immunohistochemical stains will be performed to confirm the diagnosis. These tumors can be mixed (have other components), but a tumor with any NEC component no matter how small, should be treated as so. Of note, sometimes the neuroendocrine component of the cancer may be missed on a tissue biopsy and will not be made until more tissue is obtained, such as at the time of surgery.

Once a tissue diagnosis has been made, further investigation will be made to determine the extent of spread of disease, or the stage of disease. Two different staging systems have been used to describe this disease. The FIGO system is the one used to describe all cervical cancers, while the two-tiered system used to describe small cell carcinomas of the lung is also used (see tables with staging). Although cervical cancer is typically staged clinically (based on exam with limited imaging such as a chest X-ray), when there is a known diagnosis of NEC of the cervix prior to starting treatment, more extensive workup is recommended. Given the aggressive nature of the disease and the propensity for early metastases (spread of disease beyond the cervix), additional imaging of the chest and abdominopelvic cavities is recommended. This can be accomplished with CT imaging. PET/CT imaging may also be considered, although trials are lacking to prove its superiority over routine CT scan in this disease. More dedicated imaging may be required based on symptomatology or findings on initial imaging such as a bone scan or brain imaging. Equally important to imaging, referral to a gynecologic oncologist for a thorough pelvic exam is essential to help to determine if surgical resection is appropriate.