Histopathological analysis of anaplastic thyroid carcinoma cases with long-term survival: A report from the Anaplastic Thyroid Carcinoma Research Consortium of Japan

Abstract

The aim of this study was to clarify the histopathological features of anaplastic thyroid carcinoma in patients who achieved long-term survival. We reviewed 88 anaplastic thyroid carcinoma cases in which the patient survived less than 3 months (short-term survival), and 68 anaplastic thyroid carcinoma cases in which the patient survived more than one year (long-term survival) from the database of the Anaplastic Thyroid Carcinoma Research Consortium of Japan. We examined these cases both histologically and immunohistochemically. Six (6.8%) short-term survival cases and 27 (39.7%) long-term survival cases were considered not to be anaplastic thyroid carcinoma after central review. Of these, 12 were revised to papillary carcinoma with squamous cell carcinoma. In cases without chemotherapy, long-term survival was significantly more common if there was a pre-existing tumor, epithelial growth, or lymphocytic infiltration, and short-term survival was more common if neutrophilic infiltration was present. In cases with chemotherapy, long-term survival was significantly more common if epithelial growth or a squamous cell carcinoma component was present, whereas short-term survival was more common in cases with rhabdoid cells. Immunohistochemical results were not related to survival. Some long-term survival cases showed histological findings other than those typically associated with anaplastic thyroid carcinoma. The presence of a pre-existing tumor, epithelial growth, a squamous cell carcinoma component, no neutrophilic infiltration and lymphocytic infiltration may therefore be favorable prognostic factors in anaplastic thyroid carcinoma.

Comparison of sonographic characteristics of primary thyroid lymphoma and anaplastic thyroid carcinoma

“…It is the most lethal form of thyroid malignancies, with a high rate of regional and distant spread and a grave prognosis (2)(3)(4). Primary thyroid lymphoma (PTL) is also an uncommon disease, representing less than 5% of thyroid malignancies.…”

How to confirm or deny high‐risk thyroid carcinoma is a challenge for pathologists

“…Although Ki67 proliferation index measurements have significant observer variations and measurement errors, a safety margin of 20% may be enough to avoid aggressive treatments to non‐UC cases, as Ki‐67 proliferation index of PDC are usually between 10 and 30% . This cut‐off value was also supported by Hirokawa's study, and they could show majority (60/92, 65.2%) of UC cases, confirmed by their central review board, had more than 50% labelling index …”

“…From the review of 156 cases collected by the Anaplastic Thyroid Carcinoma Research Consortium of Japan, 27 (39.9%) of the long‐term (more than 1 year) survival cases and 6 (6.8%) of the short‐term survival (less than 3 months) cases were reclassified as non‐UC. Of the non‐UC cases, 22 (66.6%) were reclassified as papillary thyroid carcinoma (PTC), including PTC with squamous cell carcinoma (12 cases), PTC with squamous metaplasia (3 cases), PTC with focal insular components (2 cases), PTC with columnar cell variants (2 cases) and PTC with a diffuse sclerosing variants (1 case) . The other non‐UC cases included poorly differentiated carcinoma (PDC) (2 cases), intrathyroid epithelial thymoma/carcinoma showing thymus‐like differentiation (2 cases), squamous cell carcinoma (1 case), mucoepidermoid carcinoma (1 case), malignant lymphoma (1 case), atypical adenoma (1 case), granulation tissue reaction (1 case) and metastatic carcinoma (1 case) .…”

“…Of the non‐UC cases, 22 (66.6%) were reclassified as papillary thyroid carcinoma (PTC), including PTC with squamous cell carcinoma (12 cases), PTC with squamous metaplasia (3 cases), PTC with focal insular components (2 cases), PTC with columnar cell variants (2 cases) and PTC with a diffuse sclerosing variants (1 case) . The other non‐UC cases included poorly differentiated carcinoma (PDC) (2 cases), intrathyroid epithelial thymoma/carcinoma showing thymus‐like differentiation (2 cases), squamous cell carcinoma (1 case), mucoepidermoid carcinoma (1 case), malignant lymphoma (1 case), atypical adenoma (1 case), granulation tissue reaction (1 case) and metastatic carcinoma (1 case) . It is of note that squamous cell components and spindle cell components often create this misinterpretation and lead to overdiagnosis.…”

“…The other non‐UC cases included poorly differentiated carcinoma (PDC) (2 cases), intrathyroid epithelial thymoma/carcinoma showing thymus‐like differentiation (2 cases), squamous cell carcinoma (1 case), mucoepidermoid carcinoma (1 case), malignant lymphoma (1 case), atypical adenoma (1 case), granulation tissue reaction (1 case) and metastatic carcinoma (1 case) . It is of note that squamous cell components and spindle cell components often create this misinterpretation and lead to overdiagnosis. We would like to introduce a solution for this dilemma for pathologists to confirm or deny high‐risk thyroid carcinoma .…”