CARCINOMA OF THE PARATHYROID GLAND

CARCINOMA OF THE PARATHYROID GLAND
Satish R Rao*, Deepak M Parikh**
*Resident; **Consultant Surgeon; Dept. of Surgery, Tata Memorial Hospital, Parel,
Mumbai - 400 012.

We report two cases of carcinoma of the parathyroid gland, which is a rare tumour. Features which make one suspect carcinoma in a case of hyperparathyroidism, and criteria for labelling a parathyroid tumour as carcinoma are discussed.

INTRODUCTION

Carcinoma of the parathyroid gland (CA.PTH) is an extremely rare entity. Thirty-four cases of hyperparathyroidism were seen in our institute during a span of 45 years. Only two were diagnosed as CA.PTH, the rest being parathyroid hyperplasia / adenomas / multiple adenomas. Because of the rarity of the lesion, the correct diagnosis is often missed. We present two such cases where parathyroid carcinomas were mistaken for thyroid nodules.

CASE REPORTS

The first patient was a forty six year old female who presented with a pathological fracture of the right femur for which internal fixation had been done. She also had a painless swelling of the left lower alveolus of two months duration. She had a past history of mental irritability, vomiting and generalized weakness. Her general condition was good except for slight difficulty in walking. Local examination revealed a swelling in a left lower alveolus, 5 x 2 cm with a smooth surface; the mucosa was intact. She also had a nodule in the left lobe of the thyroid gland, size 2 x 1.5 cm. Radiological findings revealed a cystic lesion in the left alveolus and ascending ramus of the mandible (Fig. 1). In addition, there were osteolytic lesions in the occipital and parietal areas of the skull. A thyroid scan was done which was reported as normal. Her pre-operative serum calcium level was 15.1 mg%. A fine needle aspiration cytology of the nodule in the neck was reported as "Carcinoma thyroid" Our clinical diagnosis was carcinoma thyroid associated with hyperparathyroidism. She was operated in May 1990. On exploration of the neck, the intra-operative findings were [1] nodule in the right lobe of the thyroid, [2] no separate parathyroid lesion. Total thyroidectomy was done. The nodule was reported, on frozen section, as carcinoma parathyroid; this was subsequently confirmed by the final histopathology report. There was no plane of cleavage between the parathyroid lesion and the thyroid gland. Post-operative serum calcium level dropped to 9.6 mg% and has remained normal till her last follow-up in 1995, five years after surgery. There was complete regression of the osteolytic lesions in the skull and the mandible, within six months after surgery.

The second patient was a thirty two year old male who presented with a swelling in the right lobe of the thyroid gland and left maxillary swelling with ulceration of five months duration. Fine needle aspiration of the thyroid nodule revealed the lesion to be a cyst with colloid material. Biopsy of the maxillary swelling was reported as giant cell epulis. His pre-operative serum calcium was 12.3 mg%. A thallium - technetium subtraction scan was done which revealed an enlarged right inferior parathyroid gland (Fig. 2). It was decided to explore the neck for a parathyroid lesion. He underwent a right hemithyroidectomy and right inferior parathyroidectomy. The opposite neck was not explored. The final histopathology report revealed a well-differentiated follicular carcinoma of the thyroid gland along with a parathyroid adenoma. Six months later, at the follow-up, we observed that there was no regression in the size of the maxillary swelling. His serum calcium done on this follow-up was 12.3 mg%. It was felt that a second adenoma has been left behind; hence we decided to explore the neck again. On exploration of the neck, the left inferior parathyroid gland was found enlarged with areas of haemorrhage. It was excised along with the left lobe of thyroid gland. It is our policy to do a total thyroidectomy for carcinoma of the thyroid gland. The final histopathology report revealed a parathyroid carcinoma (Fig. 3), and no residual follicular carcinoma in the left lobe of the thyroid. Post operative serum calcium was normal and the patient was asymptomatic till his last follow-up, one year after the operation.

Fig. 1 : CT scan showing an osteolytic lesion in the left side of the left side of the mandible. Fig. 2 : Thallium-technitium subtraction scan showing a lesion in the right inferior parathyroid gland.

DISCUSSION

Shantz and Castleman [1] reviewed seventy cases of carcinoma of the parathyroid gland, collected over a forty year period. They laid down the histological criteria for the diagnosis of parathyroid carcinoma. The principal histological features that distinguish parathyroid carcinoma from adenoma are trabecular pattern, mitotic figures, thick fibrosis, capsular and blood vessel invasion. Although all these criteria are not invariably found in a given case, several are usually present. Evidence of capsular invasion is the single most important criterion, diagnostic of carcinoma parathyroid. More recently, Bondeson [2] studied histopathological variables and DNA cytometry in carcinoma parathyroid. He concluded that a minority of carcinomas had a bland cytological appearance and differed from benign lesion only by their invasiveness. Certain patterns of fibrosis of malignancy. Mitotic activity constituted a prognostic risk factor but was of limited dignostic significance. The presence of macronucleoli was another important feature. Studies of nuclear DNA content by cytometric analysis are promising but not totally conclusive. Obara et al [3] state that aneuploidy was strongly associated with clinical malignancy.

Fujimoto and Obara [4] have found that serum calcium was more than 14 mg% in 39-75% of parathyroid carcinomas. Similar observation has been made by other workers. [1], [5,6] Thallium-technetium subtraction scan is useful in localizing parathyroid lesions. However in our case, thallium - technetium scan, done before the first operation, did not detect the parathyroid carcinoma on the left side.

Cohn et al [6] have stressed the importance of intra-operative recognition of parathyroid carcinoma at the time of initial operation. They mention that parathyroid carcinoma should be suspected in a hypercalcaemic patient with a palpable neck mass, tumour with a firm texture, grey appearance and adherence to surrounding tissues. They recommend an en bloc resection to include ipsilateral thyroid lobe and dissection of the tracheo oesophageal groove. A radical neck dissection should be done for extensive cervical node metastases. Nodes in the central compartment should be routinely excised.

They suggest that parathyroid carcinoma patients should be evaluated carefully by serumcalcium level, once in three months. The serum calcium is the most reliable indicator of tumour recurrence. Recurrence of carcinoma parathyroid is accompanied by hypercalcaemia, which is progressive and may require palliative resection. Sandelin et al. [7] felt that surgical resection proved most effective in some of the patients for both local recurrence and distant metastases. They have suggested other palliative measures, that include biphosphonates and gallium nitrate, which have been found to be effective in controlling hypercalcaemia. Intravenous saline followed by injection frusemide also helps to lower serum calcium level.

Carcinomas of the thyroid with parathyroid lesions are known to occur in cases with multiple endocrine neoplastic syndromes (MEN). Our case is unique because both the lesions in thyroid and parathyroid were carcinomas.

Fig. 3 : History appearance of carcinoma parathyroid showing invasion of adjacent thyroid capsule.

SUMMARY

Based on the review of literature, we recommend that one should suspect a carcinoma in a case of hyperparathyroidism, if there is:

A palpable swelling in the neck.

A gland more than 3 cm in diameter as measured on ultrasound.

Serum calcium more than 14 mg%.

Intra-operatively one should inspect all four glands. Parathyroid carcinoma can be suspected if it is a hard, fibrotic greyish lesion, or there is evidence of invasion of adjacent structures or lymph node metastases.

Histological criteria to label a lesion as parathyroid carcinoma are extraglandular and capsular invasion, mitotic figures and presence of macronucleoli.

Treatment recommended is en bloc resection of the gland with ipsilateral lobectomy along with central compartment clearance. One may have to sacrifice the recurrent laryngeal nerve or strap muscles, if they are found to be involved. Adequate surgery offers the best chance of cure.

Metastases from parathyroid gland can be managed by modified neck dissection, mediastinal clearance, and excision of pulmonary metastases.

Hypercalcaemia is a known complication which is managed by debulking surgery, i.v. saline with frusemide and biphosphonates.

REFERENCES

Schantz A, Castleman B. Parathyroid carcinoma. A study of seventy cases. Cancer March 1973; 31 : 600-5.

Bondeson L, Sandelin K, Grimelius L. Histopathological variables and DNA cytometry in parathyroid carcinoma. American Journal of Surgical Pathology 1993; 17 (8) : 820-9.

Obara T, Okamoto T, Kanbe M, et al. Functioning parathyroid carcinoma : Clinico-pathologic features and rational treatment. Seminars in Surgical Oncology 1997; 13 : 134-41.

Fujimoto Y, Obara T. How to recognise and treat parathyroid carcinoma. Surg Clinics of North America April 1987; 67 (2) : 343-57.

Wang C, Gaz RD. Natural history of parathyroid carcinoma. Diagnosis, treatment and Results. American Journal of Surgery April 1985; 149 : 522-7.

Cohn K, Silverman M, Corrado J, et al. Parathyroid carcinoma : Lahey clinic experience. Surgery Dec. 1985; 98 (6) : 1095-100.

Sandelin K, Thompson NW, Bondeson L. Metastatic parathyroid carcinoma : Dilemmas in management. Surgery Dec. 1991; 110 (6) : 978-96.

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Fig. 1 : CT scan showing an osteolytic lesion in the left side of the left side of the mandible.	Fig. 2 : Thallium-technitium subtraction scan showing a lesion in the right inferior parathyroid gland.