A Bayesian Approach to a Patient With a Residual Mass After Treatment for Non-Hodgkin's Lymphoma of the Thyroid

Abstract

A 51-year-old female with a previous history of Hashimoto’s disease presented with a right neck mass. The mass was thought to involve the thyroid gland. An initial fine needle aspirate was nondiagnostic, but suspicious for lymphoma. An open incisional biopsy of the thyroid mass revealed a diffuse large B-cell lymphoma and surrounding thyroid parenchyma revealing chronic lymphocytic thyroiditis (Hashimoto’s thyroiditis). The large neoplastic lymphoid cells were strongly CD 20 positive on immunohistochemical staining. Flow cytometry revealed that 15% of the cells were abnormal B-lymphocytes with CD 19, CD20, FMC7 expression and loss of immunoglobulin lightchain expression, consistent with a B-cell lymphoma. A computed tomography scan revealed a 3 5 cm mass that involved the thyroid as well as a 1 2 cm right supraclavicular node. A staging work-up, including a positron emission tomography (PET) scan and a bone marrow biopsy, determined that she apparently had disease localized to the neck, with only the thyroid mass and the supraclavicular node demonstrating fluorodeoxyglucose (FDG) uptake. She was treated with four cycles of cyclophosphamide, doxorubicin, vincristine, prednisone, and rituximab, followed by involved-field radiation to the neck (41.40 Gy). After completion of this therapy, a firm, nontender 1.5 cm mass was still present in the right thyroid region. A repeat PET scan, performed approximately 6 weeks after the completion of the radiation, demonstrated that the thyroid mass had shrunk from 5 cm to 1.5 cm and that the supraclavicular node had disappeared. The thyroid mass was still avid for FDG uptake; no other areas of abnormality were noted. A presumptive diagnosis of residual lymphoma was made and the patient was scheduled to be admitted for reinduction chemotherapy to be followed by high-dose chemotherapy with autologous stem-cell support.