Possible Relation of p53 and mdm-2 Oncoprotein Expression in Thyroid Carcinoma: A Molecular-Pathological and Immunohistochemical Study on Paraffin-Embedded Tissue

Routinely processed tissues from a series of benign and malignant thyroid lesions were immunohistochemically investigated with antibodies against p53 and mdm-2. p53 was immunolocalized in <10% of nuclei in 2/80 nodular goiters, 2/60 follicular adenomas, 26/68 follicular carcinomas, 7/40 papillary carcinomas, 3/10 “insular” carcinomas, and 10/31 anaplastic carcinomas. More than 10% positively stained nuclei were found in 2 widely invasive follicular, 2 insular, and 15 anaplastic carcinomas. All p53-positive cases showed a concomitant immunohistochemical mdm-2 expression; an immunohistochemical colocalization on serial section was demonstrated in 12 anaplastic carcinomas. Screening by polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP) analysis of these 12 cases revealed no relevant mutations in the coding regions of exons 2–11 of the p53 gene. Additionally, 1 follicular adenoma, 6 follicular carcinomas (4 minimally and 2 widely invasive), 1 papillary, and 2 poorly differentiated insular carcinomas were mdm-2 positive without immunohistochemically detectable p53 expression. These results provide evidence that wild-type p53 expression in thyroid carcinomas may be associated with mdm-2 induced formation of stable complexes. However, the role of p53 mutations and p53 protein inactivation owing to other factors (e.g., mdm-2) in the progression of thyroid carcinomas is still poorly understood.     

The association of well-differentiated thyroid carcinoma with insular or anaplastic thyroid carcinoma; evidence for dedifferentiation in tumor progression

The sequence of tumorigenesis in the thyroid is unclear. It has been proposed that anaplastic carcinomas of the thyroid develop by dedifferentiation in pre-existing differentiated carcinomas. We reviewed all anaplastic and insular (poorly differentiated) thyroid carcinomas in a consultation practice of thyroid pathology that included more than 400 thyroid cancers. Sixteen tumors (4%) were classified as anaplastic or insular (poorly differentiated) thyroid carcinomas. We examined these cases to determine whether these carcinomas were associated with well-differentiated neoplasms of follicular cell derivation. Ten patients were women and 6 were men, and ages ranged from 29 to 85 years; 10 patients with anaplastic carcinomas and 2 with insular carcinomas were 56 years or older, whereas 3 of the 6 patients with insular carcinomas were 31 years or younger. Four tumors were composed exclusively of anaplastic carcinoma; all were represented only by incisional biopsies. One insular carcinoma infiltrated and destroyed all underlying thyroid tissue. In the remaining total, subtotal, or hemithyroidectomy specimens, areas of well-differentiated papillary or follicular carcinoma were found. Some differentiated papillary lesions had a wide spectrum of morphologies, including Hurthle cell, tall cell, and columnar cell features. In the literature, simultaneous or previous occurrence of well-differentiated thyroid carcinomas with anaplastic carcinomas is extremely variable, ranging from 7–89% of cases. in experimental animals, serial transplantation of differentiated thyroid tumors has been shown to lead to anaplastic transformation. Our findings suggest that the majority of anaplastic thyroid carcinomas in humans arise from well-differentiated tumors. However, only a very small number of differentiated carcinomas progress to anaplastic lesions; the factors underlying this phenomenon remain to be identified.     

Immunohistochemical expression of galectin-3 in benign and malignant thyroid lesions

CONTEXT: The expression of galectin-3, a human lectin, has been shown to be highly associated with malignant behavior of thyroid lesions. DESIGN: We studied the immunohistochemical expression pattern of galectin-3 in a variety of follicular-derived thyroid lesions (13 benign and 62 malignant), including Hürthle cell and follicular carcinoma, papillary carcinomas and variants, and anaplastic and poorly differentiated carcinomas. RESULTS: Immunoreactivity was strongest in papillary thyroid carcinomas, whereas staining was less intense in Hürthle cell and anaplastic carcinomas, and even weaker in the follicular variant of papillary thyroid carcinoma. Staining was absent or weak in the 3 follicular thyroid carcinomas and was negative in both insular carcinomas. In several tumors, staining was stronger at the advancing invasive edge of the lesion than in the central portion of the tumor. Galectin-3 was also expressed focally and weakly in reactive follicular epithelium and entrapped follicles in chronic lymphocytic thyroiditis. A variety of thyroid lesions showed prominent endogenous, biotin-like activity, which could cause flaws in interpretation if a biotin-detection system were used. CONCLUSION: We conclude that galectin-3 immunostaining, when used in biotin-free detection systems, may be useful as an adjunct to distinguish benign from malignant thyroid lesions.     

Genetic alterations involved in the transition from well-differentiated to poorly differentiated and anaplastic thyroid carcinomas

Recent molecular studies have provided new insights into thyroid carcinogenesis. In thyroid papillary carcinomas at least three initiating events may occur, which are point mutations in the BRAF and RAS genes and RET/PTC rearrangements. Tumors harboring mutant BRAF and RAS are prone to progression to poorly differentiated and anaplastic carcinoma, but most likely require additional mutations to trigger this process. In thyroid follicular carcinomas, two known initiating events are RAS mutations and PAX8-PPARγ rearrangements, and RAS predisposes to dedifferentiation of follicular carcinomas. p53 and β-catenin mutations, found with increasing incidence in poorly differentiated and anaplastic carcinomas but not in well-differentiated tumors, may serve as a direct molecular trigger of tumor dedifferentiation. Additional evidence for progression from a preexisting well-differentiated carcinoma to poorly differentiated and anaplastic carcinoma comes from the studies of loss of heterozygosity and comparative genomic hybridization. Molecular studies, although limited by the lack of uniform histologic criteria for poorly differentiated carcinomas, revealed no genetic mutations or chromosomal abnormalities that are unique for poorly differentiated carcinoma and not present in well-differentiated or anaplastic carcinomas. This suggests that poorly differentiated carcinoma, as a group, represents a distinct step in the evolution from well-differentiated to anaplastic thyroid carcinoma, rather than an entirely separate type of thyroid malignancy.     

Expression of the GLUT1 glucose transporter, p63 and p53 in thyroid carcinomas

Only few studies have evaluated the usefulness of the GLUT1 and p63 status of thyroid carcinomas in revealing tumorigenesis. We studied GLUT1, p53, and p63 immunoexpression in a total of 86 cases of various thyroid carcinoma types to determine the biological significance of GLUT1 and p63 expression in thyroid carcinomas. GLUT1 was detected in six cases of anaplastic carcinoma and in one case of poorly differentiated carcinoma with membranous staining. p63 was detected in five cases of anaplastic carcinoma, in one case of poorly differentiated carcinoma, and in five cases of papillary carcinoma with nuclear positivity. p53 was detected in six cases of anaplastic carcinoma, in one case of poorly differentiated carcinoma, and in one case of follicular carcinoma with nuclear positivity. Five of seven cases of anaplastic carcinoma expressed all three of these markers. The results suggest that GLUT1, p63, and p53 are not expressed in well-differentiated thyroid carcinomas, and that they are usually expressed late in the course of thyroid tumor progression. These data strongly suggest that in anaplastic carcinomas, impairment of p53-mediated repression results in increased GLUT1 and p63 expression, and that this probably reflects the differential regulation of hypoxia-responsive pathways and basal/stem cell regulatory pathways.     

NPC2 expression in thyroid tumors and its possible diagnostic utility

Histopathologic diagnosis of thyroid lesions is sometimes difficult and may require the assistance of immunohistochemistry. Currently-used immunohistochemical biomarkers share the weakness of staining both papillary thyroid carcinoma and other non-papillary thyroid lesions. We examined NPC2 as an immunohistochemical marker in various thyroid lesions to determine the subcellular localization of the immunohistochemistry signal and evaluated the value of NPC2 as a diagnostic marker of papillary thyroid carcinoma. NPC2 immunostaining was performed on various thyroid tumors and tumor-like lesions. The immunostaining revealed significantly different patterns for papillary carcinomas and the other lesions. Papillary carcinomas exhibited moderate to strong granular cytoplasmic staining, often with basal membranous accentuation. In contrast, the other lesions showed mostly weak cytoplasmic staining, often with apical membranous accentuation. The subcellular localization of NPC2 provided insight into contrasting histopathologic morphology and reversed cellular polarity between the papillary patterns of papillary carcinomas and the follicular patterns of non-papillary carcinoma lesions. The diagnostic characteristics of NPC2 immunohistochemistry for non-follicular papillary carcinomas versus non-papillary carcinoma lesions were a sensitivity of 97.3%, specificity of 96.9%, positive predictive value of 94.7%, and negative predictive value of 98.4%. Significant differences were present between the two staining patterns in papillary carcinoma relative to mean age, nodal metastasis, and follicular and non-follicular variants (P = 0.02, P = 0.03, and P = 0.000, respectively). In conclusion, our evaluation of the subcellular localization of NPC2 using immunohistochemistry demonstrated possible value of NPC2 as a biomarker and provided insight into the morphologic characteristics of papillary carcinoma.     

Raf-1 Kinase Inhibitory Protein Expression in Thyroid Carcinomas

Raf-1 kinase inhibitory protein (RKIP) has been implicated in several fundamental signal transduction pathways that control cellular growth, differentiation, apoptosis and migration. RKIP is reduced in a variety of human carcinomas, but RKIP expression in thyroid carcinomas has not been analyzed at the protein level. In this study, we examined the immunohistochemical expression of RKIP in various subtypes of thyroid carcinoma. Immunostaining for RKIP was performed on 104 cases of primary thyroid carcinoma (40 papillary, 29 follicular, 11 medullary, 11 poorly differentiated, and 13 anaplastic carcinomas) and 26 cases of nodal metastatic tumor (17 papillary, 4 medullary, and 5 anaplastic carcinomas). Normal thyroid tissue and all cases of follicular, papillary, and medullary carcinomas showed uniform, strong cytoplasmic immunoreactivity for RKIP. With the exception of one case, poorly differentiated carcinomas also revealed strong RKIP expression. In contrast, RKIP expression was completely absent in all anaplastic carcinomas. The transition zone from the differentiated carcinoma component (strong RKIP expression) to the anaplastic carcinoma component (no RKIP expression) demonstrated a completely opposite pattern of RKIP immunoreactivity. This reduction of RKIP expression in anaplastic carcinoma was statistically significant (P?<?0.0001). Additionally, RKIP expression of nodal metastatic tumors corresponded with that of primary tumors: metastatic papillary and medullary carcinomas showed uniform, strong cytoplasmic RKIP immunoreactivity, in contrast, in metastatic anaplastic carcinomas, RKIP expression was completely absent. RKIP expression is significantly reduced in anaplastic thyroid carcinoma as compared to other subtypes of thyroid carcinoma. Further studies are necessary to elucidate the precise mechanism of RKIP action in anaplastic thyroid carcinoma.     

Genetic Changes in Chromosomes 1p and 17p in Thyroid Cancer Progression

Little is known about the genetic alterations that occur during the progression of thyroid neoplasms. To understand better the biology of thyroid tumors, we investigated several genetic loci in benign and malignant thyroid neoplasms. Forty-one thyroid tumors (6 adenomas, 16 papillary, 14 follicular, and 5 anaplastic carcinomas) were studied. Normal and tumor cells were microdissected from paraffin-embedded tissues. DNA was used for polymerase chain reaction-based loss of heterozygosity (LOH) analysis with the following markers: D1S243 (1p35–36), D1S165 (1p36) and D1S162 (1p32), TP53 (17p13), and INT-2 (11q13). Immunohistochemistry for Ki-67 was performed. The Ki-67 labeling index (LI) was the percentage of positive tumor cells. LOH at 1p was seen in 2 of 5 (40%) informative cases of anaplastic carcinoma (2 of 2 at D1S162 and 1 of 2 at D1S165) and in 2 of 11 (18%) informative cases of follicular carcinoma (2 of 7 at D1S243, 2 of 7 at D1S165, and 1 of 6 at D1S162). One anaplastic (20%) and two follicular carcinomas (14%) had LOH in at least two of the 1p loci analyzed. None of the adenomas and papillary carcinomas had LOH at these loci. LOH at 17p and 11q13 were infrequent. Ki-67 LI was 1.4, 7, 16, and 65% in adenomas, papillary, follicular, and anaplastic carcinomas, respectively. Allelic loss at 1p may occur in aggressive types of thyroid carcinoma and may be a marker of poor prognosis. LOH at 1p may represent a late genetic event in thyroid carcinogenesis. LOH at 17p and 11q13 (MEN gene locus) is uncommon in thyroid neoplasms.     

p53 expression in anaplastic carcinomas arising from thyroid papillary carcinomas.

AIM--To study the expression of p53 tumour suppressor gene in anaplastic carcinomas arising from thyroid papillary carcinomas. METHODS--Formalin fixed, paraffin wax embedded tissues from four cases of anaplastic carcinomas associated with thyroid papillary carcinomas were studied by immunohistochemistry with two different p53 monoclonal antibodies. RESULTS--The anaplastic component showed nuclear immunostaining in two cases, but not in the other two. In all cases the papillary carcinoma component was negative. CONCLUSION--The results support the hypothesis that p53 stimulates tumour progression in thyroid tumours.     

Poorly Differentiated Thyroid Carcinoma: Diagnostic Features and Controversial Issues

Poorly differentiated thyroid carcinomas are a heterogeneous group of tumors occupying an area intermediate between well-differentiated follicular or papillary carcinoma and anaplastic carcinomas, from both a histopathogenetic and a clinical point of view. Large tumor series selected on the basis of structural and/or other morphological criteria showed that poorly differentiated carcinomas have a distinct biological behavior, and the classification of these tumors into a separate group appears justified, although strict homogeneous diagnostic criteria should be achieved and widely accepted to better characterize such tumor entity. Moreover, the identification of the prognostic parameters segregating aggressive from indolent cases has important clinical implications. Molecular data in the literature, although limited by the heterogeneous case series analyzed, identify ras alterations as the most common molecular alteration in poorly differentiated carcinomas, thus, depicting a peculiar molecular pathway in this tumor type as compared to well-differentiated follicular and papillary carcinomas. The present paper aims to review the various aspects of this tumor type, from morphology to immunohistochemistry and molecular abnormalities from a practical and daily practice-oriented point of view.     

Distribution of Leu-7 antigen (HNK-1) in thyroid tumors: its usefulness as a diagnostic marker for follicular and papillary carcinomas.

The reactivity of the anti-Leu-7 monoclonal antibody was tested in 39 neoplastic and nonneoplastic thyroid tissue specimens. These included eight colloid goiters, 14 follicular adenomas, nine papillary carcinomas, five follicular carcinomas, two medullary carcinomas, and one metastatic follicular carcinoma in bone. We observed strong cytoplasmic and/or cell membrane positivity in all follicular and papillary carcinomas, in both primary and metastatic tumors. However, the medullary thyroid carcinomas tested were negative. We also observed weak and only occasional staining with anti-Leu-7 antibody in colloid goiter and follicular adenomas. The staining in the benign thyroid lesions was usually focal, less than 10% of the cells; however, in cases of follicular and papillary carcinomas, both in primary and metastatic tumors, the staining was diffuse and strong. Some of the colloid material in colloid goiters and follicular adenomas showed faint homogenous staining with anti-Leu-7 antibody. Our findings suggest that anti-Leu-7 monoclonal antibody is a marker that may facilitate the differentiation between benign and malignant thyroid lesions, with the exception of medullary carcinoma. In addition, caution should be taken when using this antibody to diagnose metastatic lesions, as other metastatic carcinomas have also been reported to be positive. This antibody should be used in conjunction with a panel of antisera to complement a morphologic diagnosis.     

Dipeptidyl aminopeptidase IV in the cytologic diagnosis of thyroid carcinoma

Recently, the demonstration of DAP IV activity in thyroid cells aspirates has been proposed as an useful tool for the diagnosis of malignancy. We have studied the enzymatic activity of DAP IV, using the modified method of Lodja, in a series of 336 selected aspirates of the thyroid gland with the following cytologic diagnosis: 236 nodular hyperplasias, 60 follicular proliferations, eight Hashimoto's thyroiditis, eight Hürthle-cell proliferations, 20 papillary carcinomas, two anaplastic carcinomas, and two medullary carcinomas. The results were subjectively evaluated on the basis of staining intensity and extension in a minimum of 200 cells. Strong-to-moderate enzymatic activity with an extension of more than 40% of the cells were exclusively seen in follicular-cell derived carcinomas (papillary carcinoma, Hürthle-cell carcinoma, and follicular carcinoma). Medullary carcinoma, anaplastic carcinoma, and benign conditions were negative or weakly stained. Cytohistologic correlation in 88 patients operated on showed the following results: 26 nodular hyperplasia (18 nodular hyperplasia and eight follicular adenomas), 36 follicular proliferation (24 nodular hyperplasia, six, adenomas, three papillary carcinomas, three follicular carcinomas), two Hürthle-cell proliferation (one Hürthle-cell adenoma and one Hürthle-cell carcinoma), 20 papillary carcinomas, two medullary carcinomas, and two anaplastic carcinomas. DAP IV staining was moderate to strong and extensive in all malignant tumors initially diagnosed as follicular or Hürthle-cell proliferations. We conclude that DAP IV activity is present in malignant differentiated thyroid tumors of follicular cells (papillary carcinoma, follicular carcinoma, Hürthle-cell carcinoma), but it is identified neither in medullary carcinoma nor in anaplastic carcinoma. Therefore, its usefulness is restricted to the diagnosis of follicular-cell malignancies. Diagn. Cytopathol. 1998;19:4–8. © 1998 Wiley-Liss, Inc.     

Bcl-2 and p53 expression in insular and in well-differentiated thyroid carcinomas with an insular pattern

Expression of p53 and bcl-2 oncogenes was investigated in poorly differentiated, so-called insular carcinomas of the thyroid gland and also in the follicular and papillary carcinomas with an insular component. Hematoxylin-eosin sections of 217 thyroid carcinomas were reevaluated for insular carcinoma and also for thyroid carcinomas with an insular component. Immunohistochemical staining method was used for detecting p53 and bcl-2 expression on paraffin blocks of three pure insular, five follicular or papillary thyroid carcinomas with a major insular component (more than 50%) and six with a minor insular component (20–50%). Flow cytometry was also performed in these cases. None of the cases showed p53 immunoreactivity. Bcl-2 expression was observed in all cases and the most intense staining was seen in insular areas. All the cases were diploid. We suggest that bcl-2 plays a role in loss of differentiation of thyroid carcinomas.     

P63 expression in papillary and anaplastic carcinomas of the thyroid gland: lack of an oncogenetic role in tumorigenesis and progression

P53 is considered one of the most important tumor suppressor genes and is mutated in up to 50% of all neoplasms. Well-differentiated thyroid carcinomas (WDTCs) only infrequently harbor p53 mutations. In contrast, these genetic alterations have been described in approximately 85% of anaplastic thyroid carcinomas and are considered a fundamental event in the malignant progression of WDTCs. However, alternative mechanisms to overcome p53 tumor suppressing properties in WDTCs and anaplastic carcinomas (ACs) have not been clarified to date. p63, a p53-homologue, has been recently characterized. In contrast to p53, p63 gene encodes six isoforms, three with transactivating and three with dominant negative (deltaN-p63) activities on p53 reporter genes. We hypothesized that overexpression of deltaN-p63 isoforms might constitute an alternative mechanism to overcome p53 tumor suppressing properties in WDTCs and ACs lacking p53 alterations. We semiquantitatively evaluated p53 and p63 immunoexpression in 12 papillary carcinomas (PC) and 11 anaplastic carcinomas. Only nuclear expression was considered specific. All PCs lacked p53 expression; at variance, nine ACs showed p53 immunoreactivity (+: 1 case; ++: 6 cases; +++: 2 cases). In PCs, p63 expression was restricted to scattered neoplastic cells juxtaposed to the basement membrane of papillary projections and to foci of squamous metaplasia. In ACs, p63 expression was observed in three cases, one of which lacked concurrent p53 immunoexpression. Our results do not support the hypothesis that p63 might constitute an alternative mechanism to overcome p53 tumor suppressing properties in thyroid neoplasms.     

Galectin-3, a marker of well-differentiated thyroid carcinoma, is expressed in thyroid nodules with cytological atypia

AIMS: The distribution of galectin-3, a widely recognized marker of well-differentiated thyroid carcinoma, was investigated in 95 thyroid lesions including nodules with foci of cytoarchitectural atypia. METHODS AND RESULTS: Twenty-eight papillary carcinomas, five follicular carcinomas, one Hurthle cell carcinoma, three poorly differentiated carcinomas, one anaplastic carcinoma, 25 nodular hyperplasias and 27 follicular adenomas, including nodules with atypical features, three neoplasms of undetermined malignant potential and two thyroiditis cases were examined. By immunohistochemistry, galectin-3 was consistently found in carcinomas; otherwise benign nodules exhibited galectin-3-positive clusters of cells with poorly developed features of differentiated carcinoma (mainly of papillary type) such as nuclear chromatin clearing, nuclear clefting, pseudoinclusions, which, in each case, were not histologically sufficient to warrant a definitive diagnosis of malignancy. In other nodules galectin-3 staining was negative. The latter were either clearly benign or showed constantly a minor degree of chromatin clearing and of other atypical features when compared with galectin-3-positive cases. CONCLUSIONS: Galectin-3, a reliable marker of differentiated thyroid carcinoma as confirmed in our series of malignant neoplasms, appears expressed in nodules with an overall benign appearance but with focal areas suspicious for malignancy. The significance of such findings needs to be further investigated.     

Immunohistochemical detection of p53 in differentiated, poorly differentiated and undifferentiated carcinomas of the thyroid

In an attempt to find whether or not p53 immunoreactivity in the thyroid gland is restricted to undifferentiated carcinomas and to evaluate the putative prognostic usefulness of its detection, we investigated p53 immunoreactivity in a series of 14 benign thyroid lesions and 65 thyroid carcinomas (12 papillary; six minimally invasive follicular; four widely invasive follicular; 31 poorly differentiated and 12 undifferentiated tumours). Unequivocal nuclear immunostaining for p53 was observed in two widely invasive follicular carcinoma (20.0%), five poorly differentiated carcinomas (16.1%) and in 10 undifferentiated carcinomas (83.3%). The percentage of immunoreactive cells was much smaller in the former groups than in undifferentiated carcinomas. Despite a trend to a more aggressive behaviour of the p53 immunoreactive cases no significant differences in the outcome of patients with positive and negative tumours was found when the comparison was made within each category of carcinomas. We conclude that p53 immunoreactivity can be detected both in undifferentiated carcinomas and in some differentiated and poorly differentiated thyroid carcinomas. Larger series of cases are necessary to evaluate the prognostic usefulness of this finding.     

BRAF mutations in anaplastic thyroid carcinoma: implications for tumor origin, diagnosis and treatment.

Anaplastic thyroid carcinoma is a highly aggressive neoplasm. Affected patients typically present with advanced disease where there is little hope for cure using conventional therapeutic modalities. Understanding the genetic alterations underlying the development of anaplastic thyroid carcinoma, such as mutational activation of BRAF, could help clarify its relationship with well-differentiated forms of thyroid carcinoma (ie follicular and papillary carcinoma) and could help select patients most likely to benefit from novel therapeutic strategies targeting BRAF. We tested 16 anaplastic thyroid carcinomas for the thymine (T) --> adenine (A) missense mutation at nucleotide 1796 in the BRAF gene using a newly developed assay that employs a novel primer extension method (Mutector assay). Seven of these anaplastic thyroid carcinomas arose in association with a well-differentiated thyroid carcinoma, and these were also evaluated. The 1796T --> A mutation was detected in eight (50%) of the anaplastic thyroid carcinomas, in four of five (80%) associated papillary thyroid carcinomas, and in zero of two (0%) associated follicular carcinomas. In all seven cases where anaplastic thyroid carcinoma arose in association with a well-differentiated thyroid carcinoma, BRAF status in the two components was concordant. Like papillary thyroid carcinoma, a significant percentage of anaplastic thyroid carcinomas also harbor BRAF mutations. Indeed, when papillary thyroid carcinoma and anaplastic thyroid carcinoma occur together, they consistently share the same BRAF profile, supporting the notion that many anaplastic thyroid carcinomas actually represent progressive malignant degeneration of a pre-existing well-differentiated thyroid carcinoma. The high frequency of BRAF mutations in a tumor that is generally regarded as uniformly fatal justifies evaluation of the potential benefits of anti-BRAF therapy for patients with anaplastic thyroid carcinoma.     

Immunohistochemical localization of metal binding proteins in thyroid tissues and tumors

Positive immunohistochemical staining for three metal binding proteins, ceruloplasmin, lactoferrin, and transferrin, has been suggested to be a reliable diagnostic marker of malignant but not benign thyroid neoplasms. We tested this hypothesis on a series of 9 nodular hyperplasias, 17 follicular adenomas, 54 papillary carcinomas, 20 follicular carcinomas, and 3 anaplastic carcinomas of thyroid using formalin-fixed paraffin-embedded tissues. We found focal staining for ceruloplasmin and lactoferrin in approximately 25% of follicular adenomas examined; focal ceruloplasmin positivity was also seen in nonneoplastic tissues surrounding thyroid neoplasms. No staining for these markers was found in malignant neoplasms or hyperplasias. Transferrin was found in 55% of papillary carcinomas, but more follicular adenomas (20%) than follicular carcinomas (11%) were positive using this antiserum. These findings show that immunostaining for these antigens is not a reliable method to distinguish benign from malignant thyroid lesions of follicular cell origin.