Incidental findings of thyroid tissue in cervical lymph nodes: old controversy not yet resolved?

Abstract

The clinical significance of papillary or follicular thyroid tissue incidentally discovered in cervical lymph nodes during pathological assessment of neck dissections for non-thyroid cancers of the upper aero-digestive tract is critically reviewed. Special emphasis is given to controversies over normal-looking, nodal, thyroid follicles. Arguments for and against the benign nature of these follicles are considered together with processes that could be involved in their formation. The admittedly limited evidence suggests that benign, thyroid follicular inclusions rarely occur in cervical lymph nodes. Histological criteria that could be helpful in recognizing the inclusions, which include assessing their extent in conjunction with the size of the node, are discussed. Finally, an algorithm based on collaboration between specialists, correlating histological findings with imaging and loco-regional control of the upper aero-digestive tract cancer, is suggested for the management of patients with incidentally discovered, nodal thyroid tissue.

Keywords: Heterotopia; Lymph nodes; Metastasis; Neck dissection; Pathology; Thyroid.

Fig. 1

Small PTC with microcalcification (arrow) and papillae (arrowhead) in a lymph node from a ND for pT1, squamous cell carcinoma (SCC) of the left floor of mouth in a male aged 61 years (unless otherwise specified the pictures are from sections stained with haematoxylin and eosin); PTC was seen in three out of 15 nodes at levels II and III; metastatic SCC was not detected (a). IHC for thyroglobulin (b), thyroid transcription factor-1 (nuclear staining) (c) and cytokeratin (CK) 19 (d)

Fig. 2

Papillae are les conspicuous here, but grooved/overlapping nuclei are arrowed. Level III lymph node from a ND for a pTX N2b, SCC in a male aged 68 years.

Fig. 3

A collection of < 10, colloid containing, thyroid follicles lined by cuboidal epithelium in the capsule of a level IIA, cervical lymph node from a ND for pT4a N1, SCC of the left mandibular alveolus in a male aged 56 years. Lymphoid parenchyma and perinodal fat are seen at the upper left and lower right of the picture, respectively.