Expression of glial filament protein (GFP) in nerve sheaths and non-neural cells re-examined using monoclonal antibodies, with special emphasis on the co-expression of GFP and cytokeratins in epithelial cells of human salivary gland and pleomorphic adenomas

We describe two novel monoclonal antibodies specific for glial filament protein (GFP), i.e., GF12.23 and GF12.24 (both IgG2a]. These cross-react over a broad range of species with epitopes located in the alpha-helical rod domain typical of all intermediate filament (IF) proteins. These monoclonal antibodies were used, in conjunction with other monoclonal GFP antibodies, rabbit antiserum to GFP, and various antibodies to other cytoskeletal proteins, to examine the occurrence of GFP in cells outside of the central nervous system of rodents, cows, and humans. We detected some scattered GFP-containing cells in the neural sheaths in some species but not in others, and we obtained different results when comparing the rabbit antisera with the monoclonal GFP antibodies. In the enteric glia of rats, we observed GFP-positive cells with all of the antibodies used, whereas in human intestine, the various monoclonal antibodies showed no reaction with any intestinal cells. Similarly, no GFP was detected in surface cells of the lens of cows and rats using any of the GFP antibodies, whereas some reaction was seen in murine lens tissue. We were also unable to detect GFP-positive cells in human, bovine, or rat liver with any of the monoclonal antibodies, which is in contrast to the reactivity of the rabbit GFP antisera with some stellate perisinusoidal cells of rat but not bovine or human liver. The possible reasons for the discrepancies between the different species and the different antibody preparations used are discussed. In addition, using double-label immunofluorescence microscopy, we showed that normal human parotid glands contain a certain type of epithelial cell that co-expresses cytokeratins and desmosomal proteins with GFP. The histological distribution of these GFP-positive cells suggests that they represent a subset of the myoepithelial cells present in this tissue. Cells co-expressing cytokeratins and GFP - in some cases, apparently together with vimentin as the third IF protein present - were also identified in tumors derived from this salivary-gland epithelium, i.e., pleomorphic adenomas, in which GFP-positive cells were relatively frequent in the myxoid and chondroid components, thus confirming the work of other investigators. Possible implications for the concept of histogenesis of these tumor cells are discussed, as are possible mechanisms resulting in the co-expression of IF proteins.

Epidermal growth factor receptors in parathyroid tumors

Hyperparathyroidism is caused by parathyroid adenomas, hyperplastic parathyroid glands, or rarely parathyroid carcinoma. Membrane receptors to epidermal growth factor (EGF), a growth-stimulating polypeptide, have been shown in other endocrine tissues such as thyroid, breast, and ovary, but not in parathyroid glands. Therefore we studied abnormal parathyroid glands from fourteen patients for the presence of EGF receptors. The binding of radioiodine-labeled EGF to the crude membrane fractions was studied using competitive inhibition with unlabeled EGF. In ten patients with solitary parathyroid adenomas, seven adenomas had no EGF binding, three had low affinity EGF binding with dissociation constants (Kd) of 28 to 148 nM and maximal specific binding (Bmax) of 285 to 1944 fmole/mg protein. In two patients with multiple adenomas, a high affinity EGF binding with Kd of 0.28 to 2.8 nM and Bmax of 6.7 to 43 fmole/mg protein was found. In one patient with hyperplastic parathyroid glands secondary to renal failure, a high affinity EGF binding with Kd of 1.7 nM and Bmax of 18 fmole/mg protein was found. In one patient with persistent hyperparathyroidism following a successful renal transplant (tertiary hyperparathyroidism), a low affinity EGF binding with Kd of 25 nM and Bmax of 219 fmole/mg protein was found. The binding of EGF did not correlate with the preoperative serum calcium or PTH levels. Thus, hyperplastic parathyroid glands (either primary or secondary) have high affinity EGF receptors whereas solitary parathyroid adenomas do not.

Flow cytometry of renal oncocytoma: common occurrence of deoxyribonucleic acid polyploidy and aneuploidy

Flow cytometry was performed on 51 typical specimens of renal oncocytoma. Nuclei were extracted from paraffin-embedded archival material and isolated nuclei were stained with propidium iodide. Of the 51 available tissue blocks 86 per cent were evaluable and 50 per cent of these samples showed a deoxyribonucleic acid (DNA) histogram that was approximately the same as normal renal parenchyma. Of the oncocytoma samples 39 per cent showed a marked increase (more than 10 per cent of the nuclei) in the tetraploid DNA peak, while 11 per cent showed a distinct DNA aneuploid peak. Among 21 evaluable grade 2 oncocytic renal tumors 33 per cent showed a normal DNA histogram, 43 per cent showed a marked increase in the DNA tetraploid peak and 24 per cent showed a DNA aneuploid peak. The common presence of polyploid nuclei containing double quantities of chromosomal DNA may correlate with the long-standing pathological observation that oncocytic tumors often contain a distinct population of large nuclei. Indeed, 86 per cent concurrence was seen between the detection of an abnormal DNA content by flow cytometry and the histopathological presence of large abnormal nuclei in these specimens. Since renal oncocytomas (grade 1 oncocytic tumors) rarely, if ever, metastasize and are relatively noninvasive locally, their markedly abnormal flow cytometry patterns are of considerable interest. Moreover, DNA polyploidy has not been identified previously in renal tumors. The biological significance and mechanism of DNA polyploidy, and the relationship of DNA polyploidy and DNA aneuploidy to the pathogenesis of oncocytic renal tumors require further laboratory investigation. The clinical use of flow cytometry to classify and to predict the behavior of renal tumors will be complicated, since renal oncocytomas commonly have polyploid and aneuploid DNA histograms.

Oncocytic tumours of the salivary gland, kidney, and thyroid: nuclear DNA patterns studied by flow cytometry

Nuclear DNA ploidy studies were performed by flow cytometry on extracted nuclei from 12 oncocytic tumours of the salivary gland, 65 oncocytic tumours of the kidney, and 37 oncocytic tumours of the thyroid gland from the pathology archives of the Mayo Clinic. In order to provide an interesting clinical spectrum, three different classes of well-differentiated oncocytic tumours were selected for examination. Salivary gland oncocytic tumours were chosen for their generally benign behaviour. Oncocytic thyroid cancers exhibiting malignant potential because of local invasion, were thought to represent the opposite extreme of aggressiveness. Renal oncocytic tumours were known to demonstrate an intermediate degree of malignancy. All of the oncocytic salivary gland tumours showed a 'normal' DNA histogram and had a benign clinical course. For the oncocytic tumours of the kidney, 45% of DNA histograms were normal, 40% exhibited a significant increase in the DNA tetraploid/polyploid (4C) peak, and 15% showed a DNA aneuploid peak. Three patients with a DNA tetraploid pattern developed tumour metastasis and two have died from metastatic renal cancer. Among the oncocytic thyroid cancers, 27% were normal, 22% exhibited an increased DNA tetraploid peak, and 51% had a distinct DNA aneuploid peak. None of the thyroid tumour patients with a normal DNA pattern or with an increased DNA tetraploid peak died as a result of thyroid malignancy. In contrast, 58% of patients whose thyroid tumours showed a DNA aneuploid peak subsequently died from thyroid cancer.

DNA content and the adenoma-carcinoma sequence in the colorectum

DNA content was measured in 269 benign adenomas and 203 adenocarcinomas of the large bowel by flow cytometry. Nuclear suspensions were prepared by pepsin digestion of paraffin sections, and an adjacent section was graded histologically by one observer. Aneuploid adenomas included five of 134 (4%) showing mild dysplasia, 19 of 107 (18%) showing moderate dysplasia, and 10 of 28 (36%) showing severe dysplasia. The association between aneuploidy and grade of epithelial dysplasia was highly significant. This gives support to the adenoma (dysplasia)-carcinoma hypothesis. Carcinomas showing aneuploidy included 18 of 29 (62%) well differentiated, 92 of 144 (64%) moderately differentiated, and 19 of 30 (63%) poorly differentiated cases. There was no relation between aneuploidy and grade of carcinoma. These findings indicate an important biological difference between adenoma and carcinoma.

Characterization of immunoreactive corticotropin and corticotropin-releasing factor in human adrenal and ovarian tumours

The distribution of immunoreactive ACTH (I-ACTH) and corticotropin-releasing factor (I-CRF) in the human adrenal was determined and these peptides were indentified in adrenocortical adenomas from patients with primary aldosteronism. Cushing's syndrome, and ovarian tumours and compared with the results in phaeochromocytomas. I-ACTH and I-CRF, mainly localized in the adrenal medulla from patients without endocrine disorders, showed a good correlation with the epinephrine concentrations. I-ACTH and I-CRF were present in all the above-mentioned tumours. Gel filtration of I-ACTH and I-CRF from these tumours showed the presence of large molecular weight forms of these peptides as well as authentic peptides. The trypsinization study of I-CRF from phaeochromocytoma suggested that such large molecular weight forms were the precursors of authentic CRF. High performance liquid chromatography showed I-CRF in these tumours to be similar to hypothalamic CRF. Phaeochromocytoma tissue slices incorporated [3H]leucine into ACTH and CRF. These findings raised the possibility that I-ACTH and I-CRF are synthesized and processed in phaeochromocytoma.

Prognostic value of nuclear DNA content in follicular thyroid tumours

The prognostic value of nuclear DNA content in follicular thyroid tumours was studied in 65 patients. Forty-six (20 with follicular carcinoma and 26 with follicular adenoma) were alive at least 10 years after diagnosis, and 19 had died of follicular thyroid carcinoma 2 months to 13 years after diagnosis. DNA was measured in morphologically identified single tumour cells either on material from fine-needle aspiration biopsy or on histologic sections from the primary tumours. Metastases or locally recurrent tumour were also examined in ten cases. The tumours from the surviving patients had cells with DNA content comparable to that in normal cells, whereas the tumours from the nonsurvivors showed higher DNA values. Primary tumours had essentially the same DNA content as metastases or local recurrence in eight of the ten studied cases. The data suggest that DNA measurement in follicular thyroid tumours offers a valuable addition to standard clinical and microscopic analysis.

Immunofluorescence demonstration of tubulin and actin in estrogen-induced rat prolactinoma cells in vitro. Alteration of their distribution after bromocriptine, colchicine and cytochalasin B treatments

Cultured cells in vitro from estrogen-induced rat prolactin-secreting adenomas (prolactinomas) were examined by indirect immunofluorescence microscopy for the distribution of cytoskeletal proteins and alterations of cytoskeleton after treatment with bromocriptine, colchicine and cytochalasin B (CB). After 8 days in culture, prolactinoma cells were well expanded and developed cytoplasmic processes were seen. The cytoplasmic microtubules were observed as fine reticular networks radiating from perinuclear portions toward the cell periphery when decorated with an antibody against tubulin. On the other hand, the actin filaments showed diffuse and spotty distribution when detected with an anti-actin antibody. Contaminated fibroblasts showed a reticular distribution of microtubules and a parallel array of actin cables which corresponds to "stress fibers" throughout the cytoplasm. After treatment with bromocriptine, the reticular distribution of microtubules in prolactinoma cells changed into a coarse and sparse pattern, which was identical with the changes in the distribution of tubulin after treatment with colchicine. On the other hand, distribution of actin was not affected by bromocriptine. Bromocriptine treatment did not alter the distribution of microtubules and actin filaments in fibroblasts, whereas colchicine changed the distribution of microtubules in both prolactinoma cells and fibroblasts. CB treatment changed the localization of actin filaments in both kinds of cells. These in vitro studies indicated bromocriptine would selectively affect the cytoplasmic microtubular system of prolactinoma cells.

Presence of neuron-specific enolase and somatostatin in human parathyroid tissues

The association of parathyroid abnormalities with apudomas prompted us to examine parathyroid tissues for the presence of neuron-specific enolase and somatostatin. Enolase was present in extracts of 29 out of 29 parathyroid specimens; tissue content was significantly higher in adenoma than in hyperplasia tissues (p less than 0.005). Somatostatin was present in 14 of 33 specimens. Immunoreactive somatostatin measured in tissue extracts' fluids coeluted on Sephacryl chromatography along with synthetic somatostatin-14 in studies of two parathyroid carcinoma specimens. Since neuron-specific enolase has been found only in neural and neuroendocrine cells, our results suggest that human parathyroid glands may contain neuroendocrine elements. The differential content of neuron-specific enolase in adenoma versus hyperplasia specimens may be diagnostically useful in selected cases. The significance of the presence of somatostatin in some but not all parathyroid tumors requires further investigation. Taken together with our prior findings of gastrin and pancreatic polypeptide in some human parathyroid glands, we postulate that human parathyroid tumors contain neural crest elements.

Immunohistochemical detection of the ras oncogene p21 product in an experimental tumour and in human colorectal neoplasms

The monoclonal antibody Y13 259 to the ras oncogene protein product p21 was used in an immunohistochemical study of ras expression in human colorectal neoplasms. The ability of the antibody to detect enhanced levels of ras expression was confirmed by its use with an experimental neoplasm known to express ras at high levels. Human colonic adenocarcinomas in general showed a similar staining intensity to that seen in normal mucosa. Adenomas however showed consistently high p21 expression as indicated by staining intensity. This suggests that elevated ras expression may be important in the development of adenomas, but that high levels need not be sustained in the conversion to invasive carcinoma.

[Comparative studies on immunological property of thyroglobulins obtained from the thyroid tumor and the adjacent tissue]

The immunological properties of thyroglobulins (Tg) of individual patients, obtained from a thyroid tumor and its adjacent tissue were compared, using conventional or monoclonal antibodies against human Tg. The thyroid tumors studied were non-functioning thyroid carcinomas and functioning thyroid adenomas. In contrast to non-functioning tumors, Tg from the functioning tumors was generally iodinated at a level close to that of normal tissue, and Tg from the tissue adjacent to the tumors had a very low iodine content. The conventional antiserum and monoclonal antibodies, B2F, seemed to recognize the conformation of Tg, while C6G showed a high affinity to Tg even when unfolded or denatured. In most cases, Tg isolated from the tissue adjacent to a tumor showed a higher affinity to antibodies than Tgs of the tumor tissue, as determined by the inhibitional effect of these Tgs against the binding of standard Tg and antibody. Furthermore, the Tg of the adjacent tissue was immunologically different in nature from the standard Tg obtained from a normal thyroid gland. From these results, Tgs of tumor and the adjacent tissue in individual patients were heterogeneous in immunological property, regardless of iodine content.

Pituitary gonadotroph adenomas in old Sprague-Dawley rats

Light microscopic and immunocytologic investigation revealed focal or diffuse pituitary gonadotroph hyperplasia in 3/27 male and 3/39 female Sprague-Dawley rats over 2 years of age. Three male and 2 female rats exhibited proliferation of morphologically abnormal gonadotrophs which were described as nodules, and 4 male and 5 female rats possessed gonadotroph adenomas which contained both immunoreactive beta-LH and beta-FSH. On plastic sections at the ultrastructural level, a further female rat was found to possess focal gonadotroph hyperplasia, 2 male and 2 female rats, gonadotroph nodules and 2 male and 2 female rats gonadotroph adenomas. While extensive gonadotroph and thyrotroph hyperplasia was observed in the nontumorous portion of the 2 pituitaries harboring thyrotroph adenoma, widespread gonadrotroph hyperplasia was noted in only 2 of 13 pituitaries with gonadotroph adenoma. Gonadotroph adenomas appeared to develop from discrete foci of morphologically altered gonadotrophs. These foci probably then progressed to form nodules and subsequently adenomas. Gonadotrophs within the nodules were often similar in morphology to adenomatous gonadotrophs whereas the earlier, smaller lesions were pleomorphic or more commonly trabecular in appearance. Serum LH levels were measured in some animals. As a group, rats displaying changes in gonadotroph morphology had a higher mean serum LH level than those without these changes, however, the values ranging from 23-249 ng/ml were well within the normal serum LH levels reported in aging rats. Gonadotroph adenomas in human patients have only recently been identified with accuracy and are relatively uncommon. As in the case of rats, they do not appear to arise from a pre-existing end organ hypofunction or pre-existing gonadotroph hyperplasia. A suitable animal model, in the form of spontaneously occurring gonadotroph adenomas in aging rats, might be useful in establishing the etiology, biochemical properties and appropriate therapy for these tumors.

Bromocriptine effects on cultured human prolactin-producing pituitary adenomas: in vitro ultrastructural, morphometric, and immunoelectron microscopic studies

In an effort to better characterize the ultrastructural, morphometric, and immunocytochemical changes induced by 10(-8) M bromocriptine (BR), tumor cells from three surgically removed PRL-producing pituitary adenomas were cultured on an extracellular matrix in serum-free medium. In each instance, the treated cultures were compared to control cells at the end of 24 h and 16 days. PRL RIAs were performed on culture medium. A decrease in cell and nucleus surface area was found on day 16 in two cultures. This supports the well known shrinkage of BR-treated PRL-producing adenomas. BR induced no change in these parameters in the tumor from a third patient who was partly resistant to the drug. Changes in the secretory process were discernible as of day 1 in all three tumors, with a dramatic reduction of exocytosis and intracellular accumulation of PRL-immunoreactive granules. This induced delayed inhibition of protein synthesis, demonstrated by preembedding immunocytochemistry on day 16. These results, obtained for the first time in human PRL-producing adenomas, are informative as to the subcellular events subsequent to short term BR treatment and illustrate that secretory inhibition and tumor shrinkage are not necessarily linked.

The relationship between serum prolactin and immunocytochemical staining for prolactin in patients with pituitary macroadenomas

We have studied the relationship between mean pretreatment levels of serum prolactin and the presence of positive immunohistochemical staining for prolactin in the pituitary tumours of 55 patients. Pretreatment serum prolactin was significantly higher in patients with tumours showing many prolactin immunostaining cells than in those with none (P less than 0.001). When the pretreatment serum prolactin exceeded 6000 mU/l, the tumours contained over 90% of prolactin positive cells; one patient was an exception who had received long-term high dose bromocriptine therapy, and her tumour showed only occasional cells with positive staining. When the pretreatment serum prolactin level was under 2500 mU/l, a tumour was found which showed either no cells or fewer than 1% of cells which stained for prolactin. There was no significant difference in pretreatment serum prolactin levels between 11 patients with craniopharyngiomas and 34 patients with pituitary macroadenomas showing no prolactin immunostaining. Seventy-one percent (32) of the 45 patients with craniopharyngiomas or tumours with negative immunostaining for prolactin, had raised pretreatment serum prolactin levels (above 360 mU/l) although this was usually only slightly elevated; the levels exceeded 2500 mU/l in six (13%) of them (two craniopharyngiomas, four pituitary tumours) but in none did the levels exceed 6000 mU/l. Four of the 55 pituitary tumours showed occasional cells (less than 1%) that stained positively for growth hormone. In none of the patients with these tumours was there evidence of acromegaly or pathologically elevated circulating growth hormone levels.

Properties of thyroglobulins from normal thyroid and thyroid tumor on a concanavalin A-sepharose column

Affinity chromatography on a concanavalin A (con A)-Sepharose column is a potentially useful for the isolation of whole thyroglobulin (Tg) at least from normal thyroid tissue. In addition to being a simple procedure for the isolation of Tg, large amounts of Tg can be applied to the column and recovered in good yield with a buffer containing MeG. In gradient elution with buffer containing increasing amounts of MeG, a single but broad peak was obtained, without separation into subfractions. However, a hemagglutination-inhibition test showed that the Tg preparation eluted early from the column had less affinity for con A than the Tg preparation eluted later, suggesting a heterogeneous distribution of carbohydrate moieties among Tg preparations. When human Tg from thyroid tumor was applied to the column, tumor Tg partly passed through the column without being adsorbed. This unadsorbed Tg showed a very low affinity for lectins, con A and wheat germ agglutinin (WGA), as determined by a double diffusion reaction in agar gel. In contrast to this fraction, the Tg adsorbed on the con A-gel column showed a very strong affinity for WGA, differing from Tg of normal thyroid tissue. Therefore, tumor Tg preparation appears to have an abnormally modified carbohydrate structure, at least in part. The higher affinity for WGA (with a specificity for N-acetylglucosamine) seen in adsorbed Tg could be due to a larger amount of GlcNAc residues which bind irregularly in the carbohydrate moiety of tumor Tg.

Flow cytometry of human colorectal tumors: nuclear isolation by detergent technique

A simple one-step technique for detergent isolation and DNA staining of nuclei from mouse colon and from human colorectal tumors was investigated. Nuclear yield increased with treatment time, up to 24 h. There were only minor differences when detergent concentrations from 0 to 0.6% were used. The lowest (0.03%) concentration was most effective. No loss of nuclei was effected by cell lysis and no selectivity was observed for isolation of certain cell-cycle phases or ploidy classes from heterogeneous tumors. The nuclei were stable in the stain-detergent solution for 24 h, but lymphocytes were sensitive to the possible proteolytic activity of one of the two commercial RNase preparations. Of the total number of parenchymal nuclei in mouse liver, as estimated by a stereological method, approximately 60% were isolated by the procedure (approximately 0.9 X 10(8) nuclei/g tissue). From mouse colon the average nuclear yield was 1.8 X 10(8)/g, and from human colorectal tumors 0.9 X 10(8)/g (ranges 0.3-1.9 X 10(8]. Microscopic examination of undissolved tissue fragments from the preparation of tumors and mouse colon showed a high selectivity for isolation of epithelial and neoplastic nuclei, leaving the stroma with its nuclei almost intact.

Immunohistochemical demonstration of S-100 protein in salivary gland neoplasms

A peroxidase-antiperoxidase technique for S-100 protein has been applied to 68 salivary glands. These included 17 pleomorphic adenomas, seven adenoid cystic carcinomas, 23 adenolymphomas and a number of other neoplasms. In addition, five specimens of myoepithelial sialadenitis ('benign lymphoepithelial lesion') and five normal parotid glands were included. Consistent results were obtained, myoepithelial cells and cells in myxoid and chondroid areas in pleomorphic adenomas staining intensely. In adenoid cystic carcinoma, on the other hand, there was no staining. The adenolymphomas possessed intensely S-100 protein-positive cells in the interfollicular lymphoid areas; these were probably interdigitating reticulum cells. In addition, branching structures, probably corresponding to Langerhans' cells, were observed in the epithelium of adenolymphomas.

Transsphenoidal surgery for acromegaly--long-term results in 100 patients

A series of 100 patients with acromegaly who were operated on using the transsphenoidal microsurgical approach is presented along with a review of the literature. Emphasis is placed on long-term follow-up to assess the value of the technique. The authors caution against early normalization of growth hormone as a criterion for biologic cure in that cases of late recurrence are presented. It is proposed that 5 ng/mL baseline growth hormone values with normal dynamic testing is the most reliable way to ascertain biologic cure. Using these criteria, a cure rate of 78% for enclosed and 33% for invasive adenomata was obtained. No long-term recurrence was seen in patients considered cured along these lines.

Characterization of microheterogeneity of human thyroglobulin from different thyroid disorders

Human thyroglobulin (Tg) was isolated to apparent purity from various thyroid tissue samples obtained after surgery. Iodine and iodothyronine content of Tg was determined. Isoelectric focussing (IEF) was performed on thin layer agarose gels. Tg revealed a microheterogeneity of 6 bands in the range between pH 4.2 and 4.6. The intensity of the single bands depended on the iodothyronine content of Tg. With increasing degree of iodination, the bands with a lower pI (pI 4.35, 4.40) became more prominent, whereas the bands with higher pI (pI 4.55, 4.60) diminished. This typical change in microheterogeneity pattern could be confirmed by kinetic in vitro iodination and consecutive iodothyronine formation of low iodinated Tg (0.05% iodine). After in vitro desialylation, the bands shifted to a higher pH range (pH 4.60 to pH 4.90), but no reduction of the number of bands occurred. Even in desialylated Tg microheterogeneity is still dependent on iodine content. These results suggest, that the microheterogeneity of Tg is influenced, but not caused by different iodine and NANA content. Different polypeptide composition may be responsible for the microheterogeneity of Tg. In thyroid diseases without disturbance in Tg synthesis (endemic, diffuse and nodular goitre, Graves' disease) variations in relative intensity of single bands could be related to differences in iodine content. In thyroid cyst fluid and cold nodules in addition to low iodinated Tg, further bands were found with pI-values comparable to desialylated Tg.

Determination and characterization of hexokinase in thyroid cancer and benign neoplasms

Hexokinase (ADP: D-hexose-6-phosphotransferase, EC 2.7.1.1) was studied in human thyroid carcinomas (n = 11), follicular adenomas (n = 32), and normal thyroid tissue (n = 21). The specific activity was significantly increased in carcinoma (0.163 +/- 0.083 U/mg protein) compared with normal tissue (0.030 +/- 0.010 U/mg protein) (P less than 0.001). Specific activities of follicular adenomas are rather heterogeneous, but when subdivided into three groups according to histopathologic criteria, a significant difference was found between follicular adenomas group I and II and follicular adenomas group III. A lesser cellular differentiation of adenomas is indicated by the lower degree or even absence of colloid production and follicle formation. A higher proliferation rate may be assumed on the grounds of the irregularities in outline, the often defective pseudocapsule, and signs of compression of the surrounding tissue. The highest specific activity in adenomas was found in the group with the highest proliferative activity, i.e., group III, whereas the lowest specific activities were found in adenomas with the lowest grade of proliferation, i.e., group I; the former was comparable with values found in carcinomas and the latter was comparable with values found in normal thyroid tissue. An interesting difference was found when the compartmentation of hexokinase was compared in carcinomas of different degree of differentiation. In papillary carcinomas a significantly lower proportion of hexokinase (HK) is present in the cytosol in comparison to follicular and undifferentiated carcinomas. In carcinomas more HK II and less HK I was found in comparison with normal thyroid tissue. In contrast hexokinase isozyme composition and compartmentation in adenomas were not different from normal thyroid tissue.