Immunohistochemical reclassification of anaplastic carcinoma reveals small and giant cell lymphoma

Abstract

Thirty-one cases of thyroid malignancies which were originally classified as anaplastic carcinoma were reexamined immunohistochemically using PAP methods (peroxidase:antiperoxidase) for IgM, IgG, IgA, cytokeratin, calcitonin, lysozyme and alpha-1-antitrypsin. The reclassification results were compared with patient data such as clinical symptoms, treatment modalities, and clinical outcome. Postoperative radiotherapy was carried out in more than 80% of cases, chemotherapy in none. Seven of 31 tumors showed a positive staining for IgM (n = 4), IgG (n = 2), and IgA (n = 1) antibodies. All of these cases were negative for epithelial markers. Surprisingly, not only all small cell tumors (n = 3) but also 4 tissues with predominantly giant cell areas were among those reclassified as primary malignant lymphoma.

Poorly Differentiated and Anaplastic Thyroid Cancer

“…Some authors suggest that new diagnostic techniques can help distinguish previously described cases of ATC from lymphoma and medullary thyroid carcinoma. [50][51][52] Other authors have postulated that since ATC is more common in iodine-deficient areas, the decline could be due to iodine prophylaxis and improved socioeconomic status. 53,54 A recent Swedish study, however, did not show any change in the incidence of ATC with the addition of iodine to their food supply.…”

“…Lymphomas stain for leukocyte-common antigen and do not have the marked cellular pleomorphism of ATC. [50][51][52] When considering the diagnosis of medullary thyroid cancer, a detailed family history is critical. A genetic workup looking for RET protooncogene mutations might be warranted in this setting.…”

Anaplastic thyroid cancer and primary thyroid lymphoma: A review of these rare thyroid malignancies

“…Data from North America published in the 1980s suggested a decline in the incidence of this rare tumor [6]. Improvements in histopathological methods leading to more accurate differentiation between ATC, TL, poorly differentiated insular follicular carcinoma, and poorly differentiated medullary thyroid carcinoma likely accounted for this apparent change in incidence [7,8].…”

Surgical management of thyroid cancer

“…The real incidence has to be re-evaluated because several cases of AC have been reclassified as lymphomas or undifferentiated medullary cancer by application of immunochemistry [81,83,84].…”