Chromogranin A immunoreactivity compared with argyrophilia, calcitonin immunoreactivity, and amyloid as tumour markers in the histopathological diagnosis of medullary (C-cell) thyroid carcinoma

Exposure to 2.45 GHz radiofrequency modulates calcitonin-dependent activity and HSP-90 protein in parafollicular cells of rat thyroid gland

In this study we analyzed the response of parafollicular cells in rat thyroid gland after exposure to radiofrequency at 2.45 GHz using a subthermal experimental diathermy model. Forty-two Sprague Dawley rats, divided into two groups of 21 rats each, were individually exposed at 0 (control), 3 or 12 W in a Gigahertz Transverse Electro-Magnetic (GTEM) chamber for 30 min. After radiation, we used simple or fluorescence immunohistochemistry to measure calcitonin cells or cellular stress levels, indicated by the presence hyperplasia of parafollicular cells, heat shock protein (HSP) 90. Immunomarking of calcitonin-positive cells was statistically significant higher in the thyroid tissue of rats exposed to 2.45 GHz radiofrequency and cell hyperplasia appeared 90 min after radiation at the SAR levels studied. At the same time, co-localized expression of HSP-90 and calcitonin in parafollicular cells was statistically significant attenuated 90 min after radiation and remained statistically significantly low 24 h after radiation, even though parafollicular cell levels normalized. These facts indicate that subthermal radiofrequency (RF) at 2.45 GHz constitutes a negative external stress stimulus that alters the activity and homeostasis of parafollicular cells in the rat thyroid gland. However, further research is needed to determine if there is toxic action in human C cells.

[Thyroid C cells and their pathology: Part 2: Medullary thyroid carcinoma]

All tumours with C cell differentiation are designated as medullary carcinomas (MTC). MTC occur sporadically (75-80%) or hereditary (20-25%), the latter being part of the multiple endocrine neoplasia type 2. Familial MTC, which is commonly preceded by "neoplastic" C cell hyperplasia, is caused by autosomal-dominant inherited germ line mutation of the RET-protooncogene; dependent on the codon affected by the mutation, patients show substantially different clinical courses. Due to its morphological heterogeneity, the immunohistochemical demonstration of calcitonin is mandatory for the diagnosis of MTC. For early diagnosis of MTC calcitonin screening has been introduced in Germany and Austria approx. 10 years ago in patients with thyroid nodules; however, an increased calcitonin serum level may also be caused by "non-MEN2-associated" C cell, which is not regarded as a precursor of sporadic MTC. Very rarely tumours may show a mixed C cell-follicular cell differentiation.

Histopathology of C Cells and Medullary Thyroid Carcinoma

The human thyroid gland contains less than 0.01-0.1% calcitonin producing and secreting C cells, which in men are almost exclusively situated in an intrafollicular location; the vast majority of C cells are embryologically derived of remnants of the ultimobranchial body and ultimately of the neural crest, a small subset, however, is presumed to originate from endodermal stem cells. Thyroid tumours with C cell differentiation have been named medullary thyroid carcinoma (MTC); calcitonin is also produced and secreted by MTC which makes this peptide hormone a very useful serum marker both for early detection and clinical follow-up of patients with MTC. About 70-80% of MTC are sporadic tumours, whereas 20-30% are familial MTC which are autosomal-dominant inherited and caused by germline mutations of the RET proto-oncogene located on chromosome 10. This article summarizes the histological, immunhistochemical and molecular genetic features of C cells, C-cell hyperplasia (CCH) and MTC, emphasizing the role of diagnostic pathology.

Prevalence and clinical spectrum of nonsecretory medullary thyroid carcinoma in a series of 839 patients with sporadic medullary thyroid carcinoma

BACKGROUND

Medullary thyroid carcinoma (MTC) is characterized by the synthesis and secretion of calcitonin (Ct). MTC without Ct secretion has been reported on rare occasions. The aim of this study was to analyze the prevalence and clinical spectrum of nonsecretory MTC in two tertiary centers that cared for 839 patients with sporadic MTC.

METHODS

Clinical, biochemical, histological, and immunohistological findings, and somatic RET mutations were analyzed, and long-term follow-up was documented.

RESULTS

Seven patients with nonsecretory MTC were identified among 839 patients with sporadic MTC; thus, the prevalence rate of nonsecretory MTC was 0.83%. In these seven patients, Ct and carcinoembryonic antigen (CEA) levels were normal when MTC was initially diagnosed in the patients, despite advanced tumor stage. Ct and CEA levels remained undetectable in four patients; recurrence was indicated in one patient after 10 years of follow-up by routine anatomic imaging and increased CEA levels, and Ct levels became slightly elevated during follow-up, despite massive tumor load, in the remaining two patients. The diagnosis of MTC was confirmed by positive immunohistochemistry for Ct, CEA, and chromogranin A. A high Ki67 proliferation index (PI) (three patients) and a high proportion of RET 918-mutated cells (four patients), as well as poorly differentiated histology, were associated with aggressive biological behavior of the MTC. The prognosis for nonsecretory MTC varied between long-term survival (12.5 years) and rapid progression leading to death within 1.75 years after diagnosis.

CONCLUSIONS

The prevalence of nonsecretory MTC was low (0.83% of patients with MTC). Diagnosis was often made at a clinically advanced tumor stage. The histological and immunohistological characteristics and the clinical course and prognosis of nonsecretory MTC are markedly heterogeneous. A high Ki-67 PI and a large proportion of cells with RET 918 mutations are associated with a poor prognosis.

[Thyroid tumors]

The vast majority of thyroid tumours are epithelial. In contrast to thyroid adenoma, which is a common tumour, thyroid carcinomas make up only 1% of all human malignancies. Routine pathology is regularly confronted with a differential diagnosis involving thyroid adenoma and carcinoma, as well as particular variants of these tumours. This paper deals with the standardised gross and histological examination, as well as the impact of immunohistochemistry and intraoperative frozen sections on thyroid pathology.

Simultaneously occurring liver metastases of pheochromocytoma and medullary thyroid carcinoma--a diagnostic pitfall with clinical implications for patients with multiple endocrine neoplasia type 2a

Malignant pheochromocytoma is an exceptional complication in patients with Multiple Endocrine Neoplasia Type 2a (MEN2a). In this paper, we report on a 53-year-old male patient with an evident RET gene germline mutation, who simultaneously developed hepatic metastases of medullary thyroid carcinoma (MTC) and pheochromocytoma. Comprehensive immunohistochemical investigations were performed to elaborate markers which could be useful for differentiating between MTC metastases and pheochromocytoma, respectively. Calcitonin and CEA, in particular cytokeratins and trefoil factor family 1 (TFF1), were detectable exclusively in MTC, whereas all the other markers revealed a comparable expression in both MTC and pheochromocytoma. The only clues that could indicate a potential malignant course were size, a lack of sustentacular cells and hyaline globules, and a focal spindle cell pattern in pheochromocytoma. Owing to a wide agreement in cellular differentiation and a lack of specific, routinely applicable markers for pheochromocytomas, a comprehensive and goal-directed immunohistochemistry is required to rule out pheochromocytoma metastasis in patients with MEN2a. A misinterpretation could lead to harmful clinical complications, as shown in the present case.

Argyrophilia and chromogranin A and B immunostaining in patients with sporadic medullary thyroid carcinoma. A critical appraisal of their prognostic utility

The purpose of the present study was to evaluate the prognostic utility of tumour argyrophilia and chromogranin A (CgA) and B (CgB) immunocytochemical expression in patients with sporadic medullary thyroid carcinoma. To this end, the histo-immunocytochemical data on a consecutive series of 99 such tumours were submitted to statistical analysis. In univariate analysis, a significantly increased risk of disease progression and death was present in patients with CgA-poor and CgB-poor tumours, respectively. Multivariate analyses were performed by adding the histo-immunocytochemical variables to the final (reference) models obtained in earlier work on the same case series, in which 18 clinicopathological variables had been taken into account. This addition did not change the prognostic impact of the variables considered in the two reference models; it did, however, increase the prognostic information for overall survival, since the adjunctive contribution of CgB immunocytochemical expression (as assessed by the likelihood ratio test) was statistically significant. It is concluded that the chromogranin B immunostaining pattern of the primary tumour allows the distinction of patients with an increased risk of death. Argyrophilia and expression of chromogranin A seem instead to be of no prognostic value in patients with sporadic medullary thyroid carcinoma.

Multihormone-producing islet cell tumor of the pancreas associated with somatostatin-immunoreactive amyloid: immunohistochemical and immunoelectron microscopic studies

Pancreatic islet cell tumors, especially insulinomas, are often associated with amyloid deposition in the tumor tissue. Biochemical analysis has demonstrated that the amyloid protein from insulinoma is derived from islet amyloid polypeptide (or amylin) that is produced by tumor cells originating from beta cells of the islet of Langerhans. We examined a case of malignant pancreatic islet cell tumor with amyloid deposition in the tumor tissue using immunohistochemistry and double-labeling immunogold electron microscopy. The tumors were composed of cells producing multiple hormones, including somatostatin, gastrin, amylin, insulin, calcitonin gene-related polypeptide, and calcitonin. Amyloid deposits reacted with antisomatostatin antiserum but not with other antisera, including antiamylin. The present study demonstrated for the first time that amyloid associated with islet cell tumors is not always derived from amylin and can come from somatostatin.

The Pathology of Medullary Carcinoma of the Thyroid: Review of the Literature and Personal Experience on 62 Cases

The aim of the present review is to analyze the numerous pathological patterns of medullary carcinoma of the thyroid (MCT) and discuss the problems of differential diagnosis with other thyroid and nonthyroid tumors. In addition, morphological parameters and phenotypic features were related to the clinical outcome. The recent literature was reviewed and compared with the features of 62 MCTs observed at our institution. The most common patterns of growth are trabecular, alveolar and spindle cells, but MCT can mimic virtually all other primary thyroid tumors and some nonthyroid neoplasms. This heterogeneity has no proven implications for prognosis, but is of relevance for diagnostic purposes, as the differential diagnosis of MCT can be difficult in nonclassical cases. In agreement also with the literature data, no relationship between histopathological parameters and outcome was found in our series, although clinically aggressive tumors had a more advanced stage at presentation. Immunocytochemica demonstration of calcitonin is apparently the only valid criterion for a correct typing of MCT. Chromogranin A is an additional sensitive marker of MCT and parallels calcitonin expression in the majority of cases.

The value of cytometric DNA analysis as a prognostic tool in neuroendocrine neoplastic diseases

In several traditionally non-endocrine, common, human, neoplastic diseases, it has become well established during the last few years, that cytometric analyses of the DNA distribution pattern of the nuclei of tumour cells can be an excellent supplement to the conventional prognostic tools, (such as clinical staging and histopathologic malignancy assessments). When analogous studies of the value of DNA analysis by means of flow cytometry and/or image cytometry are made in neuroendocrine (NE) neoplastic diseases, the ensuing results often become rather disappointing. Thus, clear-cut aneuploid DNA histograms can be found in the neoplastic cell nuclei of clinically and histopathologically completely benign NE adenomas (and even hyperplastic nodules). In contrast, highly aggressive NE carcinomas not seldom reveal themselves to be composed of tumour cells with nuclei, displaying an euploid, i.e. normal, DNA pattern. Statements of this kind have been based on the results of comprehensive investigations in several laboratories, analysing such NE tumours as insulomas/insular carcinomas, bronchial/gastrointestinal carcinoids, phaeochromocytomas, paragangliomas, neuroblastomas, adenomas of the anterior pituitary gland, parathyroid adenomas, medullary carcinoma of the thyroid and Merkel-cell tumours of the skin. Thus, the prognostic value of the cytometric DNA ploidy pattern of the nuclei of neoplastic parenchymal cells is definitely lower in NE tumours than in most of the traditionally non-endocrine carcinomas and sarcomas. Data from published and unpublished series of these kinds of NE tumours, and those of prostatic and breast carcinomas with NE differentiation, are given. By means of a new, consecutive double staining technique, it was shown that in idiopathic nesidioblastosis, the hyperinsulinism is caused by beta cells with a nuclear DNA ploidy pattern of euploid type. By the same technique, it can be shown that in the pathogenesis of the hypergastrinaemia-induced ECL-cell carcinoids of the stomach, a switch from an euploid to an aneuploid nuclear DNA distribution pattern occurs in the ECL-cells when they pass from a state of hyperplasia to that of a genuine neoplasia. In neuroblastomas, a triploid (i.e. aneuploid) DNA pattern is part of an algorithm capable of predicting a 96% survival rate, whereas a diploid/tetraploid (i.e. euploid) DNA pattern predicts a 0% survival.

Diagnostic problems in medullary carcinoma of the thyroid

Medullary carcinoma of the thyroid (MCT), the tumor entity related to parafollicular C cells of the thyroid gland, is characterized by peculiar morphological, functional and behavioral features. Apart from the constant finding of calcitonin production by MCT, heterogeneous patterns of growth as well as different associations with other lesions in the setting of MEN II syndrome have been observed. This review addresses these points, as were discussed at the 1992 European School of Pathology courses. Heterogeneity of histological patterns of MCT suggests caution in the interpretation of any thyroid tumor. Immunohistochemical demonstration of calcitonin is apparently the only valid criterion for a differential diagnosis. A correct identification of MCT is important for the individual patient (to plan proper therapy) but also for patient's relatives to screen other familiar cases in the setting of MEN II syndromes.

Fatal sporadic medullary carcinoma of the thyroid

Thirteen cases of fatal sporadic medullary carcinoma of the thyroid (MCT) that killed the patient within 1 year after diagnosis were compared with 12 nonfatal MCTs with excellent prognosis. Males predominated in fatal cases whereas the reverse was true in MCTs with good prognosis. The two groups of tumors showed generally similar cytoarchitectural features. Outstanding features of fatal MCTs, as compared with nonfatal ones, included more cellular atypia, less frequent amyloid stroma and calcification, higher mitotic rate, tumor necrosis, and a generally lower proportion of neoplastic cells stained for calcitonin. We believe that the morphological features based on routine histological studies, together with immunohistochemistry, should be reported by the pathologist since they could be useful for the management and follow-up of patients with MCT.

Secretogranin IV immunoreactivity in medullary thyroid carcinoma: an immunohistochemical study of 62 cases

The presence and intracellular distribution of secretogranin IV (Sg IV) was determined on light microcop by the avidin-biotin peroxidase complex method with the monoclonal antibody (mAb) Hisl-19 in normal and hyperplastic C-cells, in 62 primary medullary thyroid carcinomas (MTCs) and in 17 MTCs in tissue from synchronous and/or metachronous lymph node metastases and in one liver metastasis. Sg IV immunoreactivity was present in almost all normal-looking and hyperplastic C-cells, in 59 of 62 (96%) of the primary tumours, in 18 of 26 (69%) lymph node metastases and in distant metastasis. Sg IV reactivity ranged from small foci of positive tumour cells to a reaction in virtually every malignant cell. Two different staining patterns were obvious: a granular cytoplasmic reactivity and a perinuclear cluster-type signal. Normal-appearing and hyperplastic C-cells were characterized by a uniform granular staining often coexisting with discrete cluster-type immunoreactivity. Various combinations of these staining patterns were observed in C-cell carcinomas. The pure cluster-type reactivity was restricted to malignant C cells and was not detected in normal-appearing and hyperplastic C-cells. In serial sections immunohistochemical results for Sg IV, calcitonin (Ct) and chromogranin A (Cg A) showed only partial correlation. Depending on the area of the tumour chosen, immunohistochemical reactivity for Ct and Cg A might not be demonstrated in neoplastic C-cells, while staining for Sg IV was retained. The amount and type of Sg IV reactivity of MTCs was not correlated with the biological behaviour of the tumours. These results indicate that mAb Hisl-19 is an excellent marker for normal, hyperplastic and neoplastic C-cells. MAb Hisl-19 is especially useful in cases with weak or questionable reactivity for Ct and Cg A. The switch from the granular pattern to the perinuclear distribution seems to indicate a malignant transformation of C-cells and might prove useful an an additional diagnostic clue.

Medullary carcinoma of the thyroid with carcinoid-like features

AIMS

To show that medullary carcinomas of the thyroid are morphologically indistinguishable from gut carcinoids: the value of histochemistry in their identification and differential diagnosis from metastatic carcinoid tumours to the thyroid and some follicular cell neoplasms.

METHODS

15 thyroid medullary carcinomas with features of gut carcinoids were histochemically studied for the presence of argyrophil and argentaffin granules, and calcitonin, thyroglobulin, and serotonin immunoreaction.

RESULTS

Histological features of midgut (classic) carcinoids were observed in two tumours, foregut carcinoids in 12, and hindgut carcinoids in one. All tumours showed, to a greater or lesser extent, a calcitonin immunoreaction and argyrophilia. These markers were present only in a small area showing a classic pattern of thyroid medullary carcinoma in the hindgut carcinoid-like neoplasm. Argentaffin granules and serotonin immunostaining occurred in occasional cells from four foregut carcinoid-like tumours. Thyroglobulin was not expressed in all cases and amyloid stroma was expressed in three.

CONCLUSIONS

In some cases a diagnosis of metastatic carcinoid tumour to the thyroid can be considered only after ruling out clinically and histochemically medullary carcinoma of the thyroid. Immunolocalisation techniques are also essential for the differentiation between medullary carcinoma and thyroid follicular cell neoplasms that resemble carcinoid tumours. It is proposed that this tumour variant to be incorporated into current classifications as another histological subtype of C cell carcinoma.

Relationship of CD15 immunoreactivity and prognosis in sporadic medullary thyroid carcinoma

Immunoreactivity with monoclonal antibody CD15 (Leu-M1) was investigated in the primary tumours, the metastases and local recurrences of 47 cases of sporadic medullary carcinoma of the thyroid (MTC). Of these tumours, 36.5% showed a varying degree of CD15 immunostaining; in 7 carcinomas the CD15 immunoreactivity was found to be significant (greater than 15% tumour cells positively stained). Staining of the amyloid stroma was observed in 3 tumours. Significantly higher epithelial CD15 positivity was seen more frequently in the group with larger tumours (greater than 4 cm) and was found exclusively in the presence of lymph node metastases. No substantial difference in the percentage of immunostained cells was seen between primary tumours and metastatic or recurrent lesions, except for two cases that revealed a significant increase in the number of CD15-immunostained cells in metastatic and recurrent lesions. Five of 7 patients with recurrences showing significant CD15 immunostaining died of cancer, while in the absence of significant CD15 staining all patients with recurrences were still alive at the conclusion of the study. The prognostic value of CD15 immunoreactivity, found by univariate analysis, becomes weaker after adjustment for the size and stage of tumour. Particularly in patients with tumour recurrences CD15 immunostaining may be of clinical relevance for the selection of patients in whom a more radical surgical approach would be justified.