Cytomorphology of small-cell (neuroendocrine) carcinoma on ThinPrep cytology as compared to conventional smears

Urinary tract cytology showing variant morphology and divergent differentiation

Urothelial carcinoma represents a diverse group of tumours with distinct histologic subtypes, each exhibiting unique cytomorphologic features, architectural growth patterns, and/or well-developed aberrant differentiation. In fact, there are more than 13 subtypes of urothelial carcinoma recognized in the 2022 WHO classification of tumours in the urinary tract. The identification of these subtypes is crucial for an accurate diagnosis of urothelial carcinoma, and many have important clinical implications. Variant/divergent features may coexist with conventional high-grade urothelial carcinoma (HGUC) or present with 100% variant morphology. In urinary tract cytology (UTC), urothelial carcinoma can display divergent differentiation, such as squamous, glandular, or small cell carcinoma differentiation. The use of cell block preparations and immunohistochemistry with available residual urine can enhance diagnostic accuracy. On the other hand, identifying urothelial carcinoma variants, including nested, micropapillary, and plasmacytoid subtypes, poses significant challenges in UTC. Many cases of these variants are only detected retrospectively after variant histology has been established from resection specimens. Moreover, some variants exhibit features inconsistent with the diagnostic criteria for HGUC according to the Paris System for Reporting Urinary Tract Cytology. Nevertheless, the rarity of pure variant morphology and the occurrence of some false negatives for these variant cases are essential to maintain the specificity of UTC overall. This review covers the histology, cytomorphology, and important clinical aspects observed in urothelial carcinoma exhibiting divergent differentiation and various urothelial carcinoma variants detected in UTC.

Liquid-based cytology and immunocytochemistry in the evaluation of a vault lesion in a postmenopausal woman

Cytological features of small cell neuroendocrine carcinoma of the cervix in a liquid-based preparation from a vault lesion.

Neuroendocrine Neoplasia of the Female Genital Tract

Neuroendocrine neoplasia is relatively uncommon in the female genital tract (FGT) and occurs at any site, most often the ovary and cervix. A unified dichotomous nomenclature, introduced by the World Health Organization Classification of Tumors in all fifth edition volumes, divides neuroendocrine neoplasms (NENs) into well-differentiated neuroendocrine tumors (NETs) and poorly differentiated neuroendocrine carcinomas (NECs). The term carcinoid tumor is retained in the ovary and represents the commonest FGT NEN. NEC is most common in the cervix and is usually admixed with another human papillomavirus-associated epithelial neoplasm. Despite shared neuroendocrine differentiation, NET and NEC show diverse etiology, morphology, and clinical behavior.

Cytomorphological features of cervical small cell neuroendocrine carcinoma in SurePath™ liquid-based cervical samples

Small cell neuroendocrine carcinoma (SCNEC) of the cervix is a rare, highly aggressive tumour with poor prognosis and high propensity for distant metastases. The cytological features of SCNEC have rarely been described in cervical samples, and to the best of our knowledge, there are no previous reports using SurePath™ liquid-based cytology. In the present report we present the cytomorphological features of histopathologically confirmed cases of cervical SCNEC in SurePath preparations. On cytological examination, all three cases demonstrated variable numbers of tumour cells, ranging from a few dispersed cells and tiny micro-biopsies to large aggregates of small tumour cells with a high nucleus-to-cytoplasmic ratio, stippled chromatin, inconspicuous nucleoli, and scant cytoplasm. Immunocytochemistry for CD56 on the cervical preparation confirmed the diagnosis in one case. The presence of small tumour cells with characteristic stippled/salt-and-pepper type nuclear chromatin were the most consistent cytological features in these cases. Knowledge of these characteristic cytological features can help in suggesting a diagnosis of SCNEC in cervical samples which can then be confirmed by immunocytochemistry.