Type of Preparation: Conventional Magnification: High Clinical History: 51 year old perimenopausal woman with large firm mass in the cervix Interpretation: Other Malignant Neoplasms: Small cell undifferentiated carcinoma Cytomorphologic Criteria: Cluster of overlapping small cells with scant cytoplasm, hyperchromatic nuclei, shows prominent nuclear molding characteristic of small cell undifferentiated carcinoma. Background tumor diathesis is present. The lower right hand side insert illustrates the finely granular, stippled chromatin and inconspicuous nucleoli as well as nuclear molding; features typical of neuroendocrine carcinoma. Explanatory Notes: It is important to recognize this tumor as distinct from poorly differentiated squamous carcinoma with small cells. The interpretation of small cell undifferentiated carcinoma should be reserved for tumors composed of small cells in which squamous or glandular differentiation is absent or minimal. In the cervix, these tumors are strongly associated with HPV 18, a feature not identified in other primary sites. The differential includes: poorly differentiated squamous carcinoma with small cells, poorly differentiated adenocarcinoma, low-grade endometrial stromal sarcoma and lymphoma. If a liquid based specimen is used, immunostaining for neuroendocrine markers (NSE, synaptophysin, chromogranin) may be useful to demonstrate neuroendocrine features. Follow-up: Small cell undifferentiated carcinoma of the cervix confirmed on biopsy