Quantitative analysis of stromal fat content of human parathyroid glands associated with thyroid diseases using computer image analysis

The Parathyroid Gland: An Overall Review of the Hidden Organ for Radiologists

Parathyroid glands are small endocrine glands that regulate calcium metabolism by producing parathyroid hormone (PTH). These are located at the back of the thyroid gland. Typically, four glands comprise the parathyroid glands, although their numbers may vary among individuals. Parathyroid diseases are related to parathyroid gland dysfunction and can be caused by problems with the parathyroid gland itself or abnormal serum calcium levels arising from renal disease. In recent years, as comprehensive health checkups have become more common, abnormal serum calcium levels are often found incidentally in blood tests, after which several additional tests, including a PTH test, ultrasonography (US), technetium-99m sestamibi parathyroid scan, single-photon-emission CT (SPECT)/CT, four-dimensional CT (4D-CT), and PET/CT, are performed for further evaluation. However, the parathyroid gland remains an organ less familiar to radiologists. Therefore, the normal anatomy, pathophysiology, imaging, and clinical findings of the parathyroid gland and its associated diseases are discussed here.

Establishing the clinical utility of autofluorescence spectroscopy for parathyroid detection

BACKGROUND

The inability of surgeons to identify parathyroid glands accurately during cervical endocrine surgery hinders patients from achieving postoperative normocalcemia. An intrinsic, near-infrared fluorescence method was developed for real-time parathyroid identification with high accuracy. This study assesses the clinical utility of this approach.

METHODS

Autofluorescence measurements were obtained from 137 patients (264 parathyroid glands) undergoing parathyroidectomy and/or thyroidectomy. Measurements were correlated to disease state, calcium levels, parathyroid hormone, vitamin D levels, age, sex, ethnicity, and body mass index. Statistical analysis identified which factors affect parathyroid detection.

RESULTS

High parathyroid fluorescence was detected consistently and showed wide variability across patients. Near-infrared fluorescence was used to identify 256 of 264 (97%) of glands correctly. The technique showed high accuracy over a wide variety of disease states, although patients with secondary hyperparathyroidism demonstrated confounding results. Analysis revealed body mass index (P < .01), disease state (P < .01), vitamin D (P < .05), and calcium levels (P < .05) account greatly for variability in signal intensity. Age, sex, parathyroid hormone, and ethnicity had no effect.

CONCLUSION

This intrinsic fluorescence-based intraoperative technique can detect nearly all parathyroid glands accurately in real time. Its discrimination capacity is largely unlimited by patient variables, but several factors affect signal intensity. These results demonstrate potential clinical utility of optical guidance for parathyroid detection.

Parathyroid invasion, nodal recurrence, and lung metastasis by papillary carcinoma of the thyroid

AIMS

Parathyroid invasion by papillary thyroid carcinoma (PTC) is found in a small proportion of surgical specimens, but the clinicopathological relevance of this phenomenon is not well understood. This study investigated the possible prognostic relevance of parathyroid invasion in PTC.

METHOD

Parathyroid involvement was seen in 14 patients with PTC, and the clinicopathological characteristics and follow up data of these patients were analysed and compared with 164 patients without parathyroid involvement, in whom histological parathyroid examination had been undertaken, and 177 other patients without parathyroid examination (341 patients without parathyroid involvement in total).

RESULTS

Parathyroid invasion was found in older patients and there were more male patients in this group than in those without parathyroid invasion. These patients had more extrathyroid extension and were frequently in an advanced stage of disease. Lung metastasis was seen in two of the 14 patients, which was significantly more than that seen in control cases. Moreover, male patients with parathyroid invasion and those who were older than 55 years had reduced disease free survival compared with those without parathyroid invasion.

CONCLUSION

Parathyroid invasion seen in thyroid carcinoma may be an important histological feature indicating a greater chance of nodal recurrence and lung metastasis.

Parathyroid gland involvement by papillary carcinoma of the thyroid gland

OBJECTIVE

To describe the phenomenon of parathyroid gland involvement by thyroid carcinoma and to explore its clinicopathologic significance.

DESIGN

We reviewed the clinicopathologic features and described the histopathologic characteristics of 20 cases of parathyroid involvement found in a series of 911 papillary thyroid carcinomas.

RESULTS

Parathyroid involvement occurred in 3 patterns: (1) direct invasion from the main tumor with an infiltrative growth, (2) invasion of the parathyroid gland with an expansive growth and formation of a pseudocapsule between the carcinoma and the parathyroid gland, and (3) metastatic deposition within the parathyroid gland itself. Among the 20 cases, 6 (30%) had primary tumors measuring 1 cm or less, and 14 (70%) had primary tumors measuring more than 1 cm. The cases with smaller primary tumors had a comparatively lower rate of nodal metastasis (50% vs 100%, P =.02). Furthermore, none of the cases with smaller primary tumors had invasion of extrathyroid structures other than parathyroid gland, but such invasion was common among the cases with larger primary tumors (0% vs 71%, P =.01).

CONCLUSION

To the best of our knowledge, this is the first report showing that parathyroid involvement occurs in papillary thyroid carcinomas even in the early stage of the disease.

Inactivating mutations of calcium-sensing receptor results in parathyroid lipohyperplasia

Familial hypocalciuric hypercalcemia (FHH) is an autosomal dominant disease characterized by mild hypercalcemia, an inappropriately high parathyroid hormone level, and absence of hypercalciuria. Heterozygous inactivating mutations of calcium-sensing receptor (CaSR) are found in about two thirds of patients with FHH. Histologic examination of parathyroid glands in FHH is reported to show normal histology or chief cell hyperplasia. Thus, histologic features of the parathyroid glands in FHH vary, and there is no clear histologic criterion that indicates FHH. The authors have encountered three hypercalcemic patients with characteristic histologic features of enlarged parathyroid glands. Clusters of parenchymal cells were mixed with fat cells, and the area of fat cells was 33% to 49% of the total area. These features are similar to those described as parathyroid lipohyperplasia. Postoperative evaluation showed that fractional excretion of calcium was low in these patients. Direct sequencing of the polymerase chain reaction product showed that the first patient was heterozygous for an already reported inactivating mutation of CaSR (P55L). The second patient was also heterozygous for a novel inactivating mutation (R220W). The third was homozygous for an inactivating mutation (Q27R). These results indicate that histologic features of parathyroid lipohyperplasia suggest the presence of inactivating mutations of CaSR.

Comparative analysis of clonality and pathology in primary and secondary hyperparathyroidism

Parathyroid adenoma and hyperplasia are the most common causes for hyperparathyroidism, and distinction between them is controversial based on the current criteria for pathological diagnosis. We studied the clonality of hyperparathyroidism and its correlation with the pathological features, analysing 39 female patients with hyperparathyroidism. Clonality was successfully detected in 12 heterozygous cases by PCR amplification of PGK-1 gene. The 12 cases yielded 14 hypercellular glands, 8 affected by primary and 6 by secondary hyperparathyroidism. The results revealed that 7 of the 8 glands with primary hyperparathyroidism showed monoclonal proliferation. Only 1 gland pathologically diagnosed as adenoma showed a polyclonal pattern. In the 4 cases with secondary hyperparathyroidism, at least one monoclonal tumour was detected in each case. Our data indicate that monoclonal tumours are more common than expected in both primary and secondary hyperparathyroidism. Monoclonal tumours and polyclonal hyperplasia can co-exist in the same patient. Comparative study of the clonality and the pathological features showed that the clonality was consistent with the diagnosis of parathyroid adenoma, whereas it was in conflict with the diagnosis of hyperplasia with multigland involvement. One of the reasons for this is that we are ignorant of the true natures of hyperparathyroidism with multigland involvement.