Radiological Category Neuroradiology Principal Modality 1 CT Principal

Case History • 35 yo Female with left neck swelling

Test Your Diagnosis Which one of the following is your choice for the appropriate

Findings and Differentials Findings: CT demonstrates a fairly well circumscribed cystic lesion in the

DISCUSSION The differential diagnosis for lateral neck cystic lesions with marginal enhancment includes: brachial

Discussion • 49 patients with minute papillary thyroid cancer (< 1 cm and clinically

Diagnosis Pathology of lesion: Metastatic papillary thyroid cancer within a necrotic cystic lymph node

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Radiological Category: Neuroradiology Principal Modality (1): CT Principal Modality (2): US Case Report #0537 Submitted by: Marcelle Mallery, M. D. Faculty reviewer: Vince Kumar, M. D. Date accepted: 01 January 2009

Case History • 35 yo Female with left neck swelling

Radiological Presentations

Test Your Diagnosis Which one of the following is your choice for the appropriate diagnosis? After your selection, go to next page. • Lymphangioma • Necrotic Lymph Node • Brachial Cleft Anomaly • Abscess

Findings and Differentials Findings: CT demonstrates a fairly well circumscribed cystic lesion in the lateral left neck posterior to the sternocleidomastoid muscle extending from the level of the hyoid bone to the level of the thyroid. The cystic lesion has HU of 21 and has mild peripheral nodular enhancement. On US, there are fluid levels within the lesion and minimal marginal flow on color doppler. The thyroid gland is normal in appearance on US. Differentials: • Lymphangioma • Necrotic Lymph Node • Brachial Cleft Anomaly • Abscess

DISCUSSION The differential diagnosis for lateral neck cystic lesions with marginal enhancment includes: brachial cleft cysts, necrotic lymph node, lymphangioma, and abscess. Branchial cleft cysts are posterior to the submandibular gland anterior to the sternocleidomastoid muscle at the carotid bifurcation. This lesion is posterior to the sternocleidomastoid. One would expect an abscess to have a thicker wall, surrounding inflammatory changes, and greater peripheral/marginal vascularity/enhancment. The top two possibilities in the differential diagnosis include necrotic lymph node or lymphangioma. Lymphangiomas are commonly posterior to the sternocleidomastoid. They are most often in the posterior triangle (75%) or submandibular region. They may have variable signal intensity on MRI due to protein content and propensity for hemorrhage which may be hyperintense on T 1. Septations are present in most. The margins of the lymphangioma and septations may demonstrate some enhancement. Necrotic/cystic lymph nodes should also be considered high on the differential diagnosis and must be excluded. Biopsy of the cystic lesion revealed nodal metastatsis from thyroid carinoma. Grossman RI, Yousem DM. Neuroradiology: The Requisites, 2 nd ed. Philadelphia, PA: Mosby Inc, 2003: 723 -750.

Discussion • 49 patients with minute papillary thyroid cancer (< 1 cm and clinically silent) • Nodal metastasis in 33 patients (67%). • Yamashita H, et al. Acta Pathol Japan. 1986 Oct ; 36(10): 1469 -75 • Clinically undetected papillary thyroid carcinomas can produce extensive lymphatic metastases. • Rare to produce distant metastasis. • Mortality rate low, as with larger papillary carcinomas • Strate SM, Lee EL, Childers JH. Cancer. 1984 Sept 15; 54(6): 1093 -1096 • Clinically occult papillary thyroid cancer can have high propensity for local recurrence and behave like large papillary thyroid cancers. • Allo MD et al. Surgery. 1988 Dec; 104(6): 971 -6

Diagnosis Pathology of lesion: Metastatic papillary thyroid cancer within a necrotic cystic lymph node Thyroid Gland Biopsy Pathology: Microscopic foci of papillary thyroid cancer