Clonality analysis performed using human androgen receptor assay in a rare case of undifferentiated thymic carcinoma coexisting with type AB thymoma.
We report a very rare case of combined thymic carcinomas: undifferentiated thymic carcinoma coexisting with type AB thymoma. The precise mechanism underlying the coexistence of these tumors remains unknown. Therefore, we used clonality analysis to ascertain whether the two tumors were clonally related. A 63-year-old woman with thyroid cancer visited our hospital. Chest computed tomography also revealed an anterior mediastinal tumor. The patient was treated with total thyroidectomy and surgery for mediastinal tumors together with left upper lobe partial resection. The mediastinal tumor was pathologically diagnosed as undifferentiated thymic carcinoma coexisting with type AB thymoma. Multiple pulmonary metastases were detected in the patient and stage IV disease was diagnosed. The tumor was treatment-resistant, and the patient received fourth-line chemotherapy. We conducted clonality analysis using an improved human androgen receptor gene-amplification assay that involves random X-chromosome inactivation through methylation, followed by methylated gene-specific PCR amplification after sample DNA digestion with HpaII, a methylation-sensitive restriction enzyme. Clonality analysis demonstrated identical X-chromosome inactivation in cells present in both thymoma and thymic carcinoma areas, and thus revealed clonal proliferation. The two lesions in the patient might have arisen through the transformation of a preexisting thymoma into a more malignant lesion.
Department of Respiratory Medicine, Kanagawa Cardiovascular and Respiratory, Yokohama, Japan.|Department of Thoracic Oncology, Kanagawa Cancer Center, Yokohama, Japan.
Fumi
F
Karino
Department of Pathology, Kanagawa Cancer Center, Yokohama, Japan.
Tomoyuki
T
Yokose
Molecular Pathology and Genetics Division, Kanagawa Cancer Center Research Institute, Yokohama, Japan.
Shoichi
S
Matsukuma
Molecular Pathology and Genetics Division, Kanagawa Cancer Center Research Institute, Yokohama, Japan.
Yohei
Y
Miyagi
Department of Thoracic Oncology, Kanagawa Cancer Center, Yokohama, Japan.
Shuji
S
Murakami
Department of Thoracic Oncology, Kanagawa Cancer Center, Yokohama, Japan.
Hiroyuki
H
Ito
Department of Thoracic Oncology, Kanagawa Cancer Center, Yokohama, Japan.
Haruhiko
H
Nakayama
Department of Thoracic Oncology, Kanagawa Cancer Center, Yokohama, Japan.
Kouzo
K
Yamada
Clonality analysis; Combined thymic carcinoma; Type AB thymoma; Undifferentiated thymic carcinoma