96 lymph node metastases and peritoneal dissemination (2-4, 6). Cervicovaginal smears are more likely to contain malignant cells in patients with UPSC than those with TEC. Kuebler et al. (4) have described that 65% (11 of 17) of the patients they studied with UPSC had positive cervicovaginal smears whereas only 35% (7 of 20) of the samples from patients with TEC showed malignant cells. Handrickson et al. (2) found that 23% (6 of 26) of patients they studied with UPSC had positive cervicovaginal smears, as compared to 5% of patients with TEC. In this study, we found that 75% (9 of 12) of the patients with UPSC had positive smears. The higher incidence of positive cervicovaginal smears in patients with UPSC may be due to several causes. The majority of UPSCs are moderately to poorly differentiated (2). It has been noted that poorly differ- entiated endometrial carcinomas are detected more readily on cervicovaginal smears than are their well-differentiated coun- terparts (7-10). Involvement of the endocervix by the tumor is also prevalent (7, 8, 10); 50% of our UPSC cases revealed endocervical invasion. The fragile nature of papillary fronds of the tumor that readily result in exfoliation may have con- tributed to the frequency of positive smears. Differential diagnosis includes a squamous cell lesion (either an invasive carcinoma or high grade squamous intraepithe- lial lesion) because squamoid cells present both singly and as clusters in a background of tumor diathesis. The squamoid cells reveal hyperchromatic nuclei and dense cytoplasm. A case of histologically proven UPSC and invasive squamous cell carcinoma of the cervix in this study was diagnosed ini- tially on the smear as squamous carcinoma. Cytology of UPSC may be difficult to distinguish from that of endocervical carcinoma, especially for papillary serous car- cinoma of the cervix (PSCC). This is because both UPSC and PSCC show tight balls of cells, small pseudopapillary groups, single cells and a tumor diathesis. However, cervical smears from patients with UPSC do not have the highly cellular smears encountered in PSCC. Furthermore, some of the cell balls in PSCC have some cytoplasm in the center of the ball (‘‘daisy’’ clusters), whereas cell balls in the more common en- dometrial carcinoma do not show the absence of nuclei in their centers (11). It may not be possible to distinguish PSC of the endometrium from PSC of the endocervix by morpholo- gy alone (4). Adenosquamous carcinoma of the endocervix may present another diagnostic pitfall. Adenosquamous carcinoma of the cervix is presented as syncytia, sheets and occasional glandular structures comprised of large pleomorphic cells with bulky dense cytoplasm and macronucleoli. Papillae and psammoma bodies are not a prominent feature of adenosquamous carci- noma (12). The recognition of these cellular smears contain- ing pleomorphic cells in sheets and papillary formations with many bare nuclei in the background of the tumor diathesis is helpful. Extrauterine carcinoma should be included in a differen- tial diagnosis despite its rarity. If fractional curettage of the J.-Y. Park, H.S. Kim, S.R. Hong, et al. endometrium and endocervix fails to show carcinoma, an ori- gin from adnexal malignancies should be considered. The prevalence of ovarian adenocarcinoma cells in cervicovaginal smears varies from 6% to 19% (13, 14). The cytologic pic- ture of primary tubal carcinoma is a small number of round or cylindrical malignant cells. Malignant cells are overlapping as they are in papillary or globular formations. The tumor cells have lacy or finely vacuolated cytoplasm with obscuring cell borders (15, 16). Tumor cells of primary Fallopian tube adenocarcinoma found in cervicovaginal smears have been relatively similar to those of UPSC, but the background is clear (without a tumor diathesis) if the disease has not infil- trated into the endometrium (13, 15, 16). When a cytologic specimen contains cells of adenocarcino- ma, it most probably indicates the presence of endometrial carcinoma. The second most probable disease that is indicated is cervical adenocarcinoma/adenosquamous carcinoma (14). In addition, abnormal Pap smears in patients with endome- trial carcinoma were significantly associated with prognostic factors such as advanced surgical stage, poor histologic grade, lymphovascular space invasion and cervical invasion (17). Cy- tologic diagnosis of UPSC should be considered when the cervicovaginal smear contains short, three-dimensional pap- illary clusters of large malignant cells with prominent nucle- oli as well as single malignant cells or bare nuclei in the back- ground of blood or necrosis. Identification of this poor prog- nostic variant of endometrial carcinoma could be clinically important and preoperative Pap smears could be useful screen- ing method although it is not a sensitive screening test for endometrial carcinoma. REFERENCES 1. Christopherson WM, Alberhasky RC, Connelly PJ. Carcinoma of the endometrium. II. Papillary adenocarcinoma: a clinical pathological study, 46 cases. Am J Clin Pathol 1982; 77: 534-40. 2. Hendrickson M, Ross J, Eifel P, Martinez A, Kempson R. Uterine papillary serous carcinoma: a highly malignant form of endometrial adenocarcinoma. Am J Surg Pathol 1982; 6: 93-108. 3. Walker AN, Mills SE. Serous papillary carcinoma of the endometri- um. A clinicopathologic study of 11 cases. Diagn Gynecol Obstet 1982; 4: 261-7. 4. Kuebler DL, Nikrui N, Bell DA. Cytologic features of endometrial papillary serous carcinoma. Acta Cytol 1989; 33: 120-6. 5. Ronnett BM, Zaino RJ, Ellenson LH, Kurman RJ. Endometrial car- cinoma. In: Kurman RJ, editor. Blaustein’s Pathology of the Female Genital Tract. 5th ed. New York: Springer, 2002; 528-33. 6. Slomovitz BM, Burke TW, Eifel PJ, Ramondetta LM, Silva EG, Jhin- gran A, Oh JC, Atkinson EN, Broaddus RR, Gershenson DM, Lu KH. Uterine papillary serous carcinoma (UPSC): a single institution review of 129 cases. Gynecol Oncol 2003; 91: 463-9. 7. Lozowski MS, Mishriki Y, Solitare GB. Factors determining the de- gree of endometrial exfoliation and their diagnostic implications in