A 58-year-old male patient was admitted to the Affiliated Hospital of Xiangnan University in September 2021. He complained of a right neck mass accompanied by pain for 1 week and had a long history of having raw salmon and raw pickled shrimp diet. Physical examination showed a soft neck, midline trachea, and no palpable thyroid mass on both sides. The palpable right sternocleidomastoid muscle had a size of approximately 5 cm × 5 cm × 3 cm, medium texture, regular shape, unclear boundary, poor mobility, no movement with swallowing, and multiple enlarged lymph nodes were palpable in the right neck and supraclavicular fossa, the largest was about 2 cm × 1 cm, with medium texture and good mobility. Blood cell count showed eosinophil count 2.1 × 10⁹/L (0.02 × 10⁹/L-0.52 × 10⁹/L), eosinophil percentage 10.4% (0.4%-8%). Routine stool examination showed no obvious abnormality. Serum IgG antibody was positive. Colour ultrasound of the neck showed multiple cystic, solid mixed echo areas in the right sternocleidomastoid muscle, with a range of about 60 mm × 25 mm × 53 mm, irregular shape, unclear boundary and uneven internal echo. The capsule of the tumour is intact, there seems to be a coiled cord inside, and the blood supply around the capsule is rich. Contrast-enhanced CT of the neck showed that the lower end of the right sternocleidomastoid muscle was significantly enlarged with uneven density, with multiple low-density areas within it, and annular enhancement was observed in the parenchyma during enhancement. Intraoperative exploration revealed that the right sternocleidomastoid muscle mass had a complete capsule. After the incision, clear fluid flowed out of the capsule accompanied by 3 white parasites slowly peristalsis. The parasite body is milky white, long band, the head segment is small, spoon-shaped, the parasite body is relatively large, its dorsal and ventral surface each has a narrow and deep concave suction groove, the front end of the body is depressed and slightly larger, the body does not segment but has transverse folds, the tail is thin. Combined with the morphological identification and epidemiological history of the patients, the infection was considered as Diphyllobothrium latum infection. After the operation, praziquantel (total dose 120 mg/kg, divided into 5 days, three times a day) was treated with deworming, and no abnormality was found in follow-up 3 months later.