A case of adenocarcinoma in the thymus

Abstract

Background : Primary thymic adenocarcinoma is extremely rare. We report such a case based on cytological findings.
Case : A 47-year-old woman undergoing regular health screening was found in chest computed tomography (CT) to had an abnormal shadow of the mediastinum. The tumor, 5 cm in diameter, was observed radiologically in the superior mediastinum, suggesting thymoma. Thoracoscopic needle biopsy indicated, malignancy, and the tumor was resected. Imprint cytology showed tumor cells with an increased nuclear/cytoplasmic (N/C) ratio scattered and proliferated in sheets or palisades in a slightly necrotic background. Glandular structures were seen in disordered nuclear arrays. Irregularly shaped nuclei had coarse nuclear chromatin. Focally, the glandular structure had mild atypia. Histologically, tumor cells had nuclear atypia and a disordered proliferated tubular or papillary nuclear arrangement. Thymus tissue with a Hassall body was observed on the cancer periphery. Immunohistochemically, tumor cells were positive for CD5. The definitive diagnosis was adenocarcinoma of the thymus.
Conclusion : Even if mediastinal tumor cytology indicates a glandular structure with mild atypia, thymic adenocarcinoma must be considered when a glandular structure with marked nuclear atypia and disordered nuclear arrays is observed.