Cervical thymic cyst

Case contributed by Domenico Nicoletti

Presentation

Swelling over the right side of neck of 1-year duration in a previous thyroidectomy for cystic papillary thyroid carcinoma.

Patient Data

Age: 25 years
Gender: Female

CT neck with contrast

ct

CT Scan of the neck showed a multiloculated fluid density lesion with enhancing septae and tiny calcification in the right parapharyngeal space, extending from below the level of mandible up to C7 vertebral level. The mass was extending posteromedially to the right sternocleidomastoid muscle extending from the level of the thyroid cartilage up to the level of the superior mediastinum. There are no suspected adenopathies or recurrence of papillary thyroid cancer.

MRI neck with contrast

mri

MR imaging reveals a peripherally enhancing multi-septated cystic lesion arising in the right side of the neck (5.5 cm in total length, and 2 x 1.5 cm in the AP and transverse dimensions), with homogenous high signals on T2-weighted and low signal on T1 weighted images. The lesion lies deep to the sternocleidomastoid muscles and anterior to the carotid sheaths. No additional enhancing lesions were noted.

pathology

Surgical excision

Histological report (translation from Italian to English)

Microscopic description

Histologically, the lesion consists of multiple cysts covered with flat, cubic and focally squamous, multilayered epithelium with thymic tissue. There are no significant atypia. There are also chronic inflammation, cholesterin granulomas with multinucleated giant cells, vasal congestion and fibrous septa. Diagnosis Morphological finding compatible with thymic multilocular cyst.

Case Discussion

Nests of thymic tissue may be found anywhere along the descent of the thymic primordia from the angle of the mandible to the mediastinum. Cervical thymic cysts are a rare form of cervical mass in children presenting with painless neck masses. Cervical thymic cysts are unusual lesions usually presenting in the 1st decade of life. Two varieties of thymic cysts have been described, thymopharyngeal duct cysts and cysts arising from degeneration of Hassall’s corpuscles within ectopic thymic remnants. A combination of CT and MRI investigations can be helpful in differentiating thymic cysts from other congenital and neoplastic masses, but the definitive diagnosis of thymic cyst requires histopathological documentation of thymic tissue. Surgical excision is considered the management of choice for thymic cysts. The differential diagnosis of cervical thymic cyst includes thyroglossal duct cyst lymphovascular malformations, branchial cleft cyst, and laryngocele, as well as benign tumors (dermoid cysts, epidermoid cysts) and malignant tumors (lymphoproliferative, soft tissue sarcoma and other metastatic lesions). In this case the suspect was nodal metastasis because cystic papillary carcinoma has a tendency toward cystic transformation. This can occur both in the primary tumor and in the metastatic lymph nodes, in which a subcortical liquefaction necrosis results in a cystic cervical mass.

Acknowledgement: Dr.ssa Chiara Gennari

Radiographer:  TSRM Fabio Imola

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