关键词: 裂头蚴病, 病理学诊断, 形态鉴定, 分子生物学鉴定, 细胞色素c氧化酶亚基1基因

Abstract:

A 69-year-old Korean ethnic female farmer from Helong City, Jilin Province, was presented. The patient has a habit of drinking raw water and eating raw cod, and reported a subcutaneous mass in the lower left abdomen for 2 years. She sought medical services at a local hospital due to gradual enlargement of the mass on April 8, 2026. Routine blood testing showed a 0.3% eosinophil percentage and an eosinophil count of 0.03 × 10⁹/L; however, no eggs were detected in stool samples using the modified Kato-Katz thick smear method. A subcutaneous mass, measuring approximately 3.0 cm × 2.0 cm, was palpated in the lower left abdomen during physical examinations, which was smooth in surface, tough in texture, absent for tenderness, good in mobility and clear in boundary, and no redness or swelling was found in local skin. Color ultrasound examinations displayed irregular and slightly strong echoes (measuring approximately 26.7 mm × 14.0 mm × 21.0 mm) in the subcutaneous fat layer of the lower left abdomen, along with low echoes of approximately 5.6 mm × 4.9 mm. A white cord-like tissue with 5.5 cm in length was peeled off from the mass, and the head of the tissue was significantly enlarged, with the maximum diameter of 0.3 cm, which was similar to plerocercoid in morphology. Hematoxylin and eosin (HE) staining of pathological sections showed chronic granulomatous inflammation in subcutaneous tissues. The white cord-like tissue was a parasite worm body, which was visible in the transverse section as a completely solid structure. There were vacuolar and tubular structures with varying sizes in the parenchyma, scattered with lime bodies. Convex and concave transverse folds were seen on the longitudinal section of the worm body, exhibiting pathological characteristics of Spirometra plerocercoid. A target band with approximately 475 bp in length was yielded from amplification of the tapeworm cytochrome c oxidase subunit 1 (cox1) gene. Sequencing and alignment showed the gene sequence had 100% similarity with the cox1 gene sequence of S. mansoni (GenBank accession number: OQ552843), and they were clustered into a clade on the phylogenetic tree. The case was diagnosed with subcutaneous sparganosis caused by infection with S. mansoni larvae, and subcutaneous sparganosis-associated granulomatous nodules were resected. Deworming with albendazole was given post-surgery, and no other abnormalities were found during follow-up.

Key words: Sparganosis, Pathological diagnosis, Morphological identification, Molecular biological identification, Cytochrome c oxidase subunit 1 gene