Extraintestinal enterobiasis presenting as a cervical mass in an immunocompromised adult after colorectal cancer surgery: a case report

Enterobius vermicularis is a common intestinal helminth, whereas extraintestinal disease is rare and may present as a tumor-like lesion. We report a 50-year-old man with common variable immunodeficiency (CVID) and prior right hemicolectomy with adjuvant chemotherapy for cecal adenocarcinoma (pT3N1bM0) who developed a slowly enlarging left-sided cervical mass during oncologic follow-up. The lesion was painless and showed no overlying skin changes. Neck ultrasonography demonstrated a hypoechoic, round mass over the sternothyroid muscle with an elongated hyperechoic compartment and no Doppler flow. Surgical excision was performed; macroscopy suggested a lymph node. Histopathology excluded malignancy and unexpectedly revealed adult Enterobius vermicularis containing eggs embedded within inflammatory stroma. C-reactive protein was mildly elevated without leukocytosis or eosinophilia. Stool examination was negative. Whole-body MRI revealed no other extraintestinal foci. Albendazole was administered in two doses separated by two weeks with clinical resolution; the patient remains under outpatient surveillance. This case highlights that ectopic enterobiasis can mimic cervical lymphadenopathy and metastatic disease, particularly in immunocompromised patients, and that histopathology is critical for diagnosis and management. • Pinworm infection can rarely present as a deep cervical mass. • Extraintestinal enterobiasis may mimic malignancy in oncology follow-up. • Histopathology is decisive when imaging is non-specific. • Consider ectopic parasites in immunodeficient hosts with atypical lesions. • Excision plus anthelmintic therapy resulted in clinical resolution.