A Malignant Phaeochromocytoma, the Largest Reported from Asia: A Case Report

A large non functioning malignant phaeochromocytoma with extensive lymph node metastases in a 65-yearold female is reported. An incidental colloid nodule of the thyroid was found. This is the largest such tumour reported from the Asian region.


INTRODUCTION
Phaeochromocytomas are rare neuroendocrine tumours derived from chromaffin cells of the adrenal medulla or sympathetic ganglia that secrete catecholamines, with 0.1% prevalence and 10% malignant potential 1 . Paroxysmal or sustained hypertension is commonly associated, while episodic headache, palpitations, blurred vision, excessive truncal sweating and dizziness may also occur. The typical clinical picture may not be present, especially when the tumours are large (>5.5 cm in size) as they are generally nonfunctional 2 . Histological features have a limited role in determining malignancy. The presence of metastases in lymph nodes, bones, lungs, liver etc and local invasion being the only reliable indicators of malignancy 1,3 . Phaeochromocytomas vary in size with an average diameter of 5 to 6 cm while the largest reported was 45 x 25 cm in size 4 . We report a patient with a clinically silent giant malignant phaeochromocytoma, to the best of our knowledge, the sixth largest published in the current literature and the largest reported in Asia.

CASE REPORT
A 65-year-old previously healthy female presented with a large abdominal mass, multiple neck lumps and loss of appetite and weight of one-year duration. She did not complain of chest pain, headache or palpitations. Her blood pressure was 120/70Hgmm. Abdominal examination revealed a large intraabdominal, firm, non ballotable mass occupying the right upper and lower quadrants. Matted left cervical lymphadenopathy and a dominant nodule in a multinodular goitre were noted.
The thyroid function tests, Vanillyl Mandellic Acid (VMA) levels and other biochemical parameters were normal. Cytology of the thyroid nodule showed a benign lesion. Biopsy of the cervical lymph nodes showed metastatic tumour deposits. CECT scan of neck, chest, abdomen and pelvis demonstrated a welldefined heterogeneously contrast enhancing mass with central necrosis in the right side of the abdomen measuring 26cm x 25cm x 11cm ( Figure 1). The right kidney was displaced towards the left and the right adrenal gland was not visualized. Multiple enlarged anterior mediastinal, left deep cervical and posterior triangle lymph nodes were identified. There were no lesions in the liver or lungs. The impression on CECT was a gastrointestinal stromal tumour (GIST) probably arising from the second part of the duodenum with lymph node metastases.
Exploratory laparotomy revealed a right-sided large encapsulated retroperitoneal tumour weighing 3800g ( Figure 2). The tissue of origin was unclear. The tumour was excised without capsular breach. There were no blood pressure fluctuations or complication during surgery and the post-operative period was uneventful. Total thyroidectomy with left cervical block dissection was performed as a second surgery. Histology confirmed the thyroid nodule to be a colloid nodule. There was no evidence of a medullary carcinoma of thyroid or parathyroid adenoma. Reevaluation of the patient excluded the possibilities of associated hereditary forms of phaeochromocytoma.

DISCUSSION
Giant phaeochromocytomas more than 20cm in diameter, are very rare entities with limited numbers of cases reported in the literature (Table 1). These tumours may present without the classical symptoms and 2 . Twenty-four-hour urinary VMA level is commonly used as a screening test to detect phaeochromocytoma but has a low sensitivity (64%) as demonstrated by the normal values seen in our case 4 . Measurements of catecholamine levels and fractionated metanephrine levels in serum and urine has a sensitivity and specificity of 98% 1,5 . Imaging by CT or MRI helps in localization of the tumour with a sensitivity of 90% to 100% where PET scan has better image resolution 6 . In the present case the CECT was non-conclusive, and instead suspected a metastatic GIST arising from the duodenum.
There is no definite histological or cytological feature that can conclusively differentiate between benign and malignant phaeochromocytomas in the absence of metastases or locoregional invasion 3 . Phaeochromocytoma of the Adrenal gland Scaled Score (PASS) can be used to determine the malignant potential with a scor However, high inter-observer and intra-observer variations are limitations of the PASS system. The size of a primary phaeochromocytoma is associated with development of metastatic disease. In our case, the tumour had metastasized to lymph nodes. Complete surgical excision is the gold standard of treatment, which has a 5-year survival rates of 95% for benign and less than 50% for malignant phaeochromocytomas 1,3 .

CONCLUSION
We report a case of a 65-year-old female, with a giant silent malignant phaeochromocytoma, the sixth largest reported in literature and the largest reported in Asia. The possibility of phaeochromocytoma should be considered in tumours involving the anatomical region of supra renal glands even though clinical, biochemical or radiological findings are nonconclusive.