Cystadenocarcinoma of the minor salivary gland arising in the upper lip: A surgical case of an inadequate cytology specimen hampering conclusive diagnosis

Abstract Cystadenocarcinoma (CAC) of the salivary gland poses a diagnostic challenge to us, as this uncommon entity is extremely difficult to diagnose pre-operatively on an inadequate sample. However, markedly few papers have described the cytological features of CAC. An 82-year-old male presented with a history of a gradual increase in size and occasional mucous drainage from a swollen reddish nodule on the right upper lip. A retrospective examination of the cytological specimens from the drainage revealed a small number of clusters and scattered single cells of severely degenerated and mildly atypical epithelial cells with hyperchromatic dense nuclei and abundant clear cytoplasm, in a background of a large amount of mucinous material. We first interpreted this finding merely as the presence of atypical cells. However, a gross examination revealed a non-capsulated and relatively well-demarcated cystic lesion, grayish to whitish in color and measuring 13×9mm in diameter, filled with mucin. A microscopic examination showed that the tumor had a central cystic cavity filled with mucinous material and was predominantly composed of the papillary proliferation of atypical columnar mucous epithelial cells with enlarged hyperchromatic nuclei, mixed with mitotic hot spots often projecting and melting into the mucinous cystic lumen, and focally involving the surrounding connective tissue. Therefore, we ultimately made a diagnosis of CAC of the minor salivary gland arising in the upper lip. Given the characteristic features of CAC, cytopathologists should be able to correctly diagnose this lesion based on multiple adequate fine needle aspiration samples.