Diagnosis of necrotic and degenerate thyroid lesions: value of immunohistochemistry

Classification of necrotic or degenerate thyroid nodules can be difficult. The aim of this study was to investigate the value of cytokeratins, thyroid-specific markers (TTF-1 and thyroglobulin) and HBME-1 antibodies in such thyroid lesions.

Twenty-eight necrotic or degenerate thyroid lesions, including four cervical cystic papillary carcinoma (CPC) metastases, were evaluated with immunohistochemistry for TTF-1, thyroglobulin, HBME-1, AE1&3, Cam5.2, MNF116 and cytokeratin (CK)19. There was loss of TTF-1 staining in all necrotic lesions, with positive staining in degenerate tumour cells of all four metastatic CPCs. Thyroglobulin was retained in 18 lesions. Dual CK19 and HBME-1 expression was seen only in six of seven necrotic papillary thyroid carcinomas and the four metastatic CPCs. Retained immunoreactivity for AE1&3 and Cam5.2 was seen in most necrotic papillary carcinomas (n = 11/11 and n = 10/11, respectively), poorly differentiated carcinomas (n = 2/3 and n = 3/3, respectively) and follicular-patterned areas of anaplastic carcinoma (n = 3/5 and n = 4/5, respectively). Cam5.2 showed spurious staining of macrophages in eight lesions.

Thyroglobulin is useful in establishing the thyroid origin of a necrotic lesion. TTF-1 may be useful for highlighting degenerate tumour cells within metastatic CPCs. Retained expression of CK19 and HBME-1 is seen in necrotic papillary carcinomas. AE1&3 is the most specific and Cam5.2 the most sensitive of the CK cocktails in non-viable thyroid lesions.