2022 Volume 71 Issue 2 Pages 356-361
Background: Adenoid cystic carcinoma (AdCC) is characterized by slow growth and a long clinical course, but dedifferentiated AdCC grows rapidly and has a poor prognosis compared with low- or high-grade AdCCs. We report four cases of dedifferentiated AdCC of the head and neck treated at our hospital. Cases: The patients were men and women aged 38 to 78 years and had both low-grade AdCC and high-grade AdCC coexisting in one tumor with extensive necrosis. The tumors were wholly or partially replaced with poorly differentiated or undifferentiated components. Highly malignant components were observed also in the cytological materials, and the characteristic findings of AdCC were hardly observed. Although it was difficult to estimate the original tissue type, it is important to carefully search for features such as cribriform structures and tubular structures. In addition, it was reported that cytological materials are useful for distinguishing between highly malignant and dedifferentiated cases. In these four cases, the cellular findings such as the degree of atypia and polymorphism, swelling of the nucleus and nucleolus, and small to medium cytoplasm were consistent with the literature. However, it should be noted that the cytological material reflects only part of the tumor. Conclusion: Cytodiagnosis is important in clinically determining the presence of dedifferentiated components and providing useful information to support histological diagnosis.
