A rapid growing cervical mass mobile while swallowing is the most common clinical presentation of severe thyroid malignancy. A 91-year-old female patient with a history of Hashimoto thyroiditis presented with clinical compressive neck symptoms. The patient had gastric Maltoma diagnosed that was surgically resected thirty years ago. A straightforward process was needed to reach full histological diagnosis and initiate prompt therapy. Ultrasound (US) showed a 67 mm hypoechoic left thyroid mass with reticulated pattern without signs of locoregional invasion. Percutaneous trans isthmic US-guided 18G core needle biopsy (CNB) disclosed diffuse large B cell lymphoma of the thyroid gland. FDG PET revealed two distinct thyroid and gastric foci (both SUVmax 39.1). Therapy was initiated rapidly to decrease clinical symptoms in this aggressive stage III primitive malignant thyroid lymphoma. The prognostic nomogram was calculated by using a seven-item scale, which disclosed a one-year overall survival rate of 52%. The patient underwent three R-CVP chemotherapy courses, then refused further treatment and died within five months. Real-time US-guided CNB approach led to rapid patient’s management that was tailored to patient’s characteristics. Transformation of Maltoma into diffuse large B cell lymphoma (DLBCL) into two body areas is deemed to be extremely rare.