Rationale:Differentiated thyroid cancer is the most common endocrine malignancy with concomitant hematological malignancy in 7%.Patient concerns:We present a case of a synchronous papillary thyroid cancer and a follicular variant of non-Hodgkin lymphoma and discuss the possible diagnostic and treatment dilemmas.Diagnosis:A 48-year-old female was reffered to our hospital with diagnosis „thyroid cancer“. Due to a history compatable of synchronous lymphoproliferative disease we performed a computed tomography, which revealed multiple enlarged lymph nodes in the neck, mediastinum, axilla and abdomen.Interventions:A total thyroidectomy with dissection of the central compartment was performed. The microscopic examination of thyroid gland revealed multifocal papilary thyroid cancer and metastaes from the same cancer plus aggressive follicular B-cell non-Hodgkin lymphoma in the lymph nodes. Despite the classic approach „solid cancer first“, due to the advanced stage of lymphoma we first started the chemotherapy of NHL. She received 8 cycles of CHOP and I131 therapy with 129 mCi. Because of incomplete response 4 cycles Mabthera plus Bendamustin were added. The follow-up PET scan revealed complete remission of lymphoma and bilaterally enlarged single cervical lymph nodes, previously known to be iodine positive on I131-SPECT/CT. She was sheduled for bilateral radical neck LND.Outcomes:Complete remission of NHL and residual single metastatic cervical lymph nodes requiring bilateral radical neck LND.Lessons:The synchronous DTC and NHL is rare. To date, there is no standardized approach due to lack of experience. We suggest lymphoma first approach with synchronized and tailored multidisciplinary efforts. The molecular mechanisms of this link are poorly understood and yet remain to be elucidated.