|Year : 2015 | Volume
| Issue : 2 | Page : 178-181
Functioning lipoadenoma of parathyroid in ectopic location
Ranjeetha Shenoy, Arun Behl
Department of Surgical Oncology, Fortis Hospital and Cancer Institute, Mulund, Mumbai, Maharashtra, India
|Date of Web Publication||6-May-2015|
#3308/1G, 13th Main Road, MCC B Block, Davangere - 577 004, Karnataka
Parathyroid adenoma is the most common cause of primary hyperparathyroidism. Parathyroid lipoadenoma is a rare and well-documented clinico-histological variant of parathyroid adenoma which owing to its bulky nature is found at aberrant locations and generally extends into the mediastinum, thus posing difficulty in diagnosis and surgical exploration. Here we present a young lady with classical signs and symptoms of primary hyper-parathyroidism who underwent excision of the single adenoma, and histologically diagnosed as a lipoadenoma. Here, we discuss the presentation and management of this rare variant.
ملخص البحث :
يعتبر ورم الغدة حول الدرقية الحميد اكبر مسبب لمرض فرط الغدة حول الدرقية. ويعتبر الورم الغدي الشحمي للغدة حول الدرقية من الأمراض النادرة ولكنه نوع موثق سريريًا ونسيجيًا لورم الغدة حول الدرقية الحميد. وبسبب حجمه يوجد هذا الورم في أماكن غير معتادة من الجسم وربما يمتد إلى المنصف مما يشكل صعوبة في التشخيص والاستكشاف الجراحي. يعرض الباحثون حالة لشابة تعاني من فرط الغدة حول الدرقية. تم استئصال الورم الحميد وتم تشخيصه نسيجيًا كحالة ورم غدي شحمي. يناقش الباحثون أعراض وعلامات وعلاج هذا النوع من الأورام.
Keywords: Hyperparathyroidism, lipoadenoma, parathyroid gland
|How to cite this article:|
Shenoy R, Behl A. Functioning lipoadenoma of parathyroid in ectopic location. Saudi J Med Med Sci 2015;3:178-81
| Introduction|| |
Lipoadenoma of parathyroid gland is an unusual type of parathyroid adenoma in which the glandular elements are associated with mature adipose tissue characterized by intermingling of chief/oxyphil cells with abundant mature adipose cells, the latter comprising 20-90% of the tumour. This variant has also been reported as parathyroid lipohyperplasia, parathyroid hamartoma, and parathyroid adenoma with myxoid stroma. Most cases are associated with hyperparathyroidism. Lipoadenoma of parathyroid gland poses difficulty in diagnosis as a cause of hyperparathyroidism, because of rarity of these lesions and overlap with normal parathyroid tissue on microscopic examination. In this report a case of a young lady with classical signs and symptoms of primary hyper-parathyroidism associated with lipo-adenoma is presented.
| Case report|| |
A 31-year-old female patient presented with a history of recurrent nephrolithiasis of 6 years duration. She consulted urologist for the same for which she was treated with six sittings of lithotripsy. She had recurrence of kidney and ureteric stones year later for which she underwent four sittings of lithotripsy and basketting. She also had episodic joint pain and swelling affecting both hands and feet past of 2 years duration, for which she used to take analgesics. Based on her complaints and serum calcium levels, a provisional diagnosis of hyperparathyroidism was made by a physician and referred to us. Physical examination was essentially normal and no swelling was palpable in the neck. Her serum calcium was 10.5 mg/dL and serum parathormone parathyroid hormone (PTH) level was 1227.7 pg/mL (normal reference range: 11-54 pg/mL). X-ray of hand showed sclerosis at the upper ends of the proximal phalanx of index and middle fingers of right hand, shaft of the proximal phalanx of left ring finger [Figure 1]. Ultrasound imaging of neck was done and revealed mixed echogenic mass with solid and cystic component measuring 4.6 cm × 2.1 cm in size seen posterior to right lobe of thyroid. Sestamibi-single-photon emission computed tomography scan was done; there was evidence of uptake in nodular mass posterior to right lobe of thyroid, mass measuring 5 cm in long axis [Figure 2]. Patient was thoroughly evaluated for medical fitness and surgical excision of parathyroid adenoma was planned. Preincision serum PTH was measured, which was 938 pg/mL. Using skin crease incision one finger-breadth above sternal notch, skin flaps were raised and right lobe of thyroid mobilized, no parathyroid enlargement could be found posteriorly. Intrathyroidal parathyroid was suspected and right hemithyroidectomy done. On sectioning the specimen, it was uniform, without any nodules. On further neck exploration, an aberrant tissue was found abutting prevertebral fascia extending inferiorly into mediastinum. It was suspected to be aberrant thyroid tissue with enlarged parathyroid. The specimen measured 5 cm × 3 cm × 2 cm. It was sent for frozen section evaluation and confirmed to be parathyroid gland. Intra-operatively the PTH assay done 10 min after excision of gland and PTH levels dropped to 125.6 units (Decay 87%), which compared to the preincision levels was considered significant decay, confirming successful parathyroidectomy. After thorough hemostasis closure was done [Figure 3]. Postoperative period was uneventful. Strict attention was given to fluid, electrolytes and calcium homeostasis. Drain was removed on the 3 rd postoperative day and patient discharged on the same day. Histopathological examination revealed it to be a rare variant "Lipomatous parathyroid adenoma (parathyroid lipo-adenoma)". Postoperative period was uneventful and there was no hypocalcemia. On follow up, the serum PTH levels returned to baseline and the patient is normocalcemic and symptom free until date.
|Figure 2: Single-photon emission computed tomography showing evidence of uptake in right side of neck|
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|Figure 3: Intra-operative photograph showing the adenoma (pointed with an artery forceps)|
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| Discussion|| |
Parathyroid adenoma is the most common cause of primary hyperparathyroidism and as much as 85% are single adenomas.  Before the advent of the serum channel autoanalyzer, patients with parathyroid adenoma were generally seen with the clinical manifestations of hypercalcemia, including painful bones, kidney stones, abdominal groans, psychic moans, and fatigue overtones. Until the 1970s, 75% of patients initially presented with nephrolithiasis. Today, however, a biochemical diagnosis is usually made before the appearance of symptoms, and many patients are asymptomatic or minimally symptomatic.  However, the same phenomenon is not observed in India. In India, asymptomatic presentation is virtually unheard of. Even the symptomatic disease is picked up late after a series of management for fractures and renal stones by the orthopedic surgeons and the urologist. Most patients present with symptomatic disease, whereas very few are screen-detected cases. This may be because of the fact that, in India, screening of the healthy population for hypercalcemia is not a routine practice and there is limited access to medical treatment, especially in the rural areas.  Widely prevalent vitamin D deficiency may be the reason for exaggerated musculo-skeletal manifestations.
Parathyroid lipoadenoma is a rare and well documented variant of parathyroid adenoma. It may occur with hyperparathyroidism and present as a neck mass. Approximately, 35 cases have been reported previously.  A parathyroid lipoadenoma is defined clinically as a single adenoma with more than 50% fat on histologic examination in conjunction with primary hyperparathyroidism and resolution of hypercalcemia postoperatively.  Lipoadenomas vary in weight and measure up several centimeters. The first reported tumor case weighed 420 g and was called "hamartoma."  Grossly, the tumors are round, oval, or lobular in shape with a smooth external surface, and show a yellow tan appearance depending upon the mount of fatty tissue component which varies from 20% to 90%, respectively. Lipoadenomas are composed of chief cells, with or without oxyphil cells, arranged in solid, trabecular, and glandular patterns, or an admixture, surrounded by prominent fatty tissue component resembling the normal adult parathyroid gland. Pure oxyphil lipoadenoma may occur. The stroma of parathyroid lipoadenomas may show inflammatory cells, calcium deposits, and myxomatous changes, which occasionally could be prominent with little interspersed lipomatous component (myxoid lipoadenoma).
Clinically most lipoadenomas of parathyroid are hyperfunctional and present with classical hyperparathyroidism, although asymptomatic and patients with questionable symptoms have been reported in series.  The tumor shows no predilection for sex, with a 1:1 female-to-male ratio, and has occurred in a wide range of ages from 41 to 92 years. Unlike parathyroid adenoma, there are no reported cases associated with multiple endocrine neoplasia.  In general, lipoadenomas are much larger than adenomas and because of their size have commonly been described as extending into the mediastinum. ,, The high fat content of the lipoadenoma makes it difficult to distinguish from normal adipose tissue with diagnostic imaging or even at the time of surgery. If the surgeon is not aware of this entity, it can easily be missed during neck exploration and result in the failure to cure the patient. 
Parathyroidectomy is the preferred management for all symptomatic primary hyperparathyroidism. Preoperative localization of parathyroid adenomas is generally not necessary before a careful neck exploration by an experienced endocrine surgeon, but it is imperative before primary exploration if unilateral exploration is desired.  Bilateral neck exploration has been traditionally performed where routine identification of all enlarged (involved) and normal parathyroid is mandatory and only enlarged gland(s) is/are excised. Of late, focused approaches for excision of single gland pathology are gaining popularity. Various techniques have been described-open minimally invasive parathyroidectomy, videoendoscopic parathyroidectomy, minimally invasive video-assisted parathyroidectomy, minimally invasive radioguided parathyroidectomy.
| Conclusion|| |
Our patient described above presented with classical renal and bone involvement. Sestamibi scan revealed right inferior parathyroid adenoma. On surgical exploration, it was atypically located just anterior to prevertebral fascia and extending into the mediastinum. There was marked fall of PTH levels intra-operatively, and tissue was confirmed parathyroid on frozen section. The histopathological examination revealed it to be a rare variant, lipomatous parathyroid adenoma (parathyroid lipoadenoma). The postoperative period was uneventful. She was followed-up regularly, and her serum calcium and PTH levels were within normal limits.
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[Figure 1], [Figure 2], [Figure 3]