Cytological features of mesonephric‐like adenocarcinoma of the uterine corpus

Although several studies have documented the histological features of uterine mesonephric‐like adenocarcinoma (MLA), its cytological features have been rarely reported.

Previous studies have reported the cytological characteristics of benign and malignant mesonephric lesions. [20][21][22] Since the first observations of abnormal cytological features in specimens obtained from mesonephric remnants and hyperplasia, 23,24 a few studies have reported the cytological features of MA and MLA. [20][21][22] Kezlarian et al. 21 reported the largest case series demonstrating the cytological features of ovarian, endometrial, and pelvic adenocarcinomas showing mesonephric-like differentiation. However, their study population did not include any cervicovaginal cytology samples. In this study, we investigated the cytological characteristics of uterine MLA in various types of cytology samples, including those obtained from the cervicovagina, pleural effusion, intraoperative peritoneal washing, and transbronchial lymph node aspiration. We also examined whether significant differences existed in cytological features according to the sampling site or preparation method.

| DISCUSSION
Regardless of the sampling site, preparation methods, or sampling time, the cytological features of MLA were relatively consistent.
Tumor cells formed tight, hyperchromatic three-dimensional clusters, showing high nuclear-to-cytoplasmic ratio. Their nuclei displayed intranuclear grooves and indentations easily identifiable at higher magnifications. However, no severe nuclear pleomorphism was present. These findings were similar to those presented in previous studies. 20 cells; however, none of them was endocervical adenocarcinoma.
These findings suggested that the lack of nuclear pseudostratification and feathering might make the pathologists who rendered the original diagnoses to argue against common types of endocervical adenocarcinoma. In case a cytology sample demonstrates features suspicious of glandular lesion but distinct from those of endocervical adenocarcinoma, uterine MLA should be included in the differential diagnosis.
We did not detect any tumor diathesis on cytology slides; however, most histology slides contained areas of tumor cell necrosis.
Given the fact that all except two smear slides were prepared using a liquid-based technique, we cannot exclude the possibility that tumor diathesis was completely removed during the preparation process.
Nevertheless, our results were consistent with that of previous studies. [20][21][22] Notably, touch imprinting slides of MA cases also failed to reveal tumor diathesis. 21,22 However, further investigations using a larger cohort are necessary to confirm these findings.
We or ADC-NOS in cytological specimens, which displayed consistent cytological features different from those of common types of endocervical adenocarcinoma. Our study had also some limitations. One such weakness might be that the examined cases were retrieved from three different institutions. However, we collected various types of cytological specimens and found that there were no significant differences in cytological features according to the sampling method or site.
In conclusion, we demonstrated that irrespective of sampling site and preparation method, most uterine MLA cases showed the following cytological features: tight three-dimensional cellular clusters showing small-to-medium-sized, round, hyperchromatic nuclei with indistinct nucleoli and high nuclear-to-cytoplasm ratio. Approximately half of the samples showed hyaline-like globules (10/21, 47.6%).