Axillary Lymph Node Metastasis of Differentiated Thyroid Carcinoma: Report of 4 Cases with Special Reference to the Metastatic Channel

It is extremely rare to develop metastasis of differentiated thyroid carcinoma to the axillary lymph nodes, non-regional lymph nodes. The metastasis is likely lymphogenous because of patients showing metastasis only in the axilla without other distant metastasis. Four of 924 patients with differentiated thyroid carcinoma who underwent curative resection in our institution and Kyoto Medical Center showed metastasis to the axilla (0.43%) during the follow-up until July, 2008 from April, 1981. The patients were aged 61-73 years old, 2 with well-differentiated and 2 poorly-differentiated papillary carcinoma, 1 male and 3 female, with 1 already having distant metastasis at a different site when axillary metastasis became clear. Furthermore, each patient had a history of neck dissection of the ipsilateral VI regional lymph nodes prior to axillary metastasis. Concerning the origin of axillar metastasis, it was previous reported that lymphatic communication is present between the cervical and axillary lymphatic clutches. When orthodromic lymphatic flow is blocked by either previous neck dissection or metastasis around the venous angle, the lymphatic system may go against the flow. The postoperative course and prognosis are presented together with the viewpoint of QOL.