Fine-Needle Aspiration of Mucin-Producing Thyroid Tumors

Abstract

Objective: Mucin-producing thyroid tumors are extremely rare. Nonetheless, we have encountered three such cases in fine-needle aspiration. We report the cytologic and histologic findings and review the literature. Study Design: Cytologic features were studied on direct smears using Romanovsky stain to detect background substance and Papanicolaou stain to analyze nuclear and cytoplasmic features. The cytologic features were correlated with histology. Mucin was demonstrated by mucicarmine, Alcian Blue/PAS, and Alcian Blue (pH 2.5). Results: The cytologic features related to mucin include: (1) thick luminal mucin globules and signet ring cells aspirated from an 83-year-old woman with a 3-cm signet ring cell follicular adenoma, (2) abundant fluffy mucin containing signet ring cells in cohesive fragments aspirated from a 75-year-old man with the bilateral signet ring cell follicular variant of papillary carcinoma, which is the first case in the English literature, and (3) abundant thin mucoid mucin aspirated from the lymph node of an 86-year-old woman with a 5-cm mucinous poorly differentiated thyroid carcinoma. Conclusion: The occurrence of mucin in thyroid fine-needle aspiration does not necessarily indicate metastasis, and the presence of mucin in cervical lymph nodes does not exclude the thyroid gland as a possible primary.

The Unique Liquid-Based Cytologic Findings of Thyroid Signet-Ring Follicular Adenoma: A Report of Two Cases with Fine Needle Aspiration Cytology

“…In addition, intracytoplasmic vacuoles were positive for mucin stains including mucicarmine, PAS and Alcian blue as in previously reported cases [1,3]. Therefore, ancillary test results are required to discriminate this rare entity from other malignancies such as metastatic signet-ring cell carcinoma of the stomach [12,13] or clear cell carcinoma of the kidney [14], especially in liquid-based cytology because more apparent nuclear atypia is seen even in a benign follicular lesion [5].…”

“…Although the histopathologic features of signet-ring follicular adenoma of the thyroid have been described in a few studies [2,7,8,9], until now, there have only been two reports on the cytomorphologic features of this tumor [1,3]. Therefore, diagnosis based on cytologic examination can be more challenging than histopathologic examination.…”

“…Although signet-ring changes are indicators for a malignancy in other groups of adenocarcinoma of the stomach and lung, interestingly, these peculiar cellular changes are more frequently found in benign lesions than in malignant thyroid lesions [15]. Immunohistochemical assays for thyroglobulin, TTF-1 and CD10 are necessary for diagnosis [1,3,14]. The exact mechanism of positivity for mucin staining in signet-ring follicular adenoma remains unclear; however, it has been suggested that the mucin reactivity is due to the presence of protein-polysaccharide complexes derived from incomplete degradation of thyroglobulin and aberrant intracellular accumulation of thyroglobulin resulting from the inability of the tumor cell to excrete it [7].…”

“…Only a few reports regarding the cytologic features of signet-ring follicular adenoma using the conventional smear preparation have been described [1,3]. Because of the rarity of the disease, the diagnosis of this unusual variant by fine needle aspiration (FNA) cytology has always been challenging.…”

Thyroid FNA: Challenges and Opportunities

“…Yang et al [12] help correct this by describing the cytomorphology of three unusual tumors: a signet-ring cell follicular adenoma, a signet-ring cell variant of the follicular variant of papillary carcinoma (a variant of a variant! ), and a mucinous poorly differentiated thyroid carcinoma.…”