Intrathyroidal Parathyroid Adenoma

Intrathyroidal parathyroid adenoma

MB, 53/F, 2011632986

• c/o-– Generalized body

ache- 3 years– Progressive proximal

myopathy- 3 years– Low backache

• No history of-– Graveluria/ Renal

stones– Neck swelling– Epigastric pain– Acute abdomen– Mood swings

• No significant family history

Examination

• No neurocutaneous markers

• P/R- 80/min

• BP- 134/84 mm Hg

• Musculo-skeletal examination- Power grade V in all groups of muscles in all limbs

Examination

• Neck-– 3x3 cm midline swelling in left lower neck– Round, soft – Moving well with deglutition

• ? Thyroid• ? Parathyroid• ??? LN

InvestigationsTest Values Normal values

Calcium 10.8-11.3 mg/dl (↑) 8.5-10.8

Phosphorus 2.6- 3.2 mg/dl 2.5-4.5

Creatinine 0.73 mg/dl 0.5-1.6

ALP 577-1082 U/L (↑) 35-150

PTH 235.4 pg/ml (↑) 9-55

25-OH Vit D 8.40 ng/ml (↓) 9-47

• CXR, Neck X ray- WNL

USG neck

• Left lobe thyroid replaced by complex cystic lesion with multiple echogenic septations measuring 3 x 2.2 x 1.6 cm

• Another 6 mm hypoechoic lesion in lower pole of left lobe thyroid

• Right lobe- 1 x 1 cm nodule

Tc99m MIBI Scan • Early images-

Focal area of increased tracer uptake in midzone of left thyroid lobe

• Delayed images- persistent abnormal activity in same site

CECT NECK

CECT NECK

FNAC Thyroid

• Occasional clusters of benign follicular epithelial cells

• Minimal amount of colloid

• Impression- Follicular pattern lesion

Surgery, 14-Mar-2012

• B/L Neck exploration with left hemithyroidectomy, frozen section biopsy, conversion to total thyroidectomy with IOPTH monitoring

• Left superior and left inferior parathyroid glands not localized in normal position

Intrathyroidal parathyroid adenoma

Surgery, 14-Mar-2012

Intrathyroidal parathyroid adenoma

13

Surgery, 14-Mar-2012

IOPTH (pg/ml)

408

179

41 36 280

50

100

150

200

250

300

350

400

450

Preincision

Preexcision

5 min 10 min 15 min

pg/ml

Gross specimen

3 x 2 x 1 cm left thyroid lobe with 1 x 1 cm yellowish nodule

Surgery, 14-Mar-2012

• Left hemithyroidectomy done & sent for frozen section biopsy

• Reported as-– Oncocytic lesion/ Parathyroid adenoma

Histopathology with IHC

Histopathology- Left lobe

• Thin encapsulated tumor• Cells arranged in diffuse sheets• Microfollicles at places• Thin vascular channels• Cells monomorphic with round nucleus and

moderate cytoplasm• No capsular or vascular invasion• IHC- Thyroglobulin was negative in nodule• IMPRESSION- Intrathyroidal parathyroid

adenoma

Histopathology- Right lobe

• Nodular goiter

Post operative course• Symptomatic hypocalcemia

on day 1- given iv calcium and oral calcium with vitamin D supplements

• Infusion tapered and stopped on day 3

• Relief in bodily pains upto 80%

• Discharged on day 5 in normocalcemic state on oral calcium and vitamin D supplements

Follow up visit

• Eucalcemic

• Free of myalgias

• Bony pains relieved by 80%

• On oral Calcium and vitamin D supplements

Review of literature

Definition

Defined as a parathyroid gland, normal or abnormal, situated totally within the thyroid, surrounded on all aspects by thyroid parenchyma

Intra-thyroidal Parathyroid

Embryologic Basis

Wang’s Hypothesis IV branchial pouch

Parathyroid, ultimobrancial body

Fusion with medial lobe thyroid

Intrathyroidal superior parathyroid

Wang CA. Hyperfunctioning intrathyroid parathyroid gland: A potential cause of failure in parathyroid surgery. JR Soc Med 1981

III Pharyngeal pouch

Thymus Inferior parathyroid (Intrathymus gland)

Primordium trapped in thyroid

Intrathyroidal inferior parathyroid

Feliciano DV. Parathyroid pathology in an intrathyroidal position. Am J Surg 1992;164:496–50

Intrathyroidal Parathyroid Adenomas as a cause for PHPT

• 1.4-3.4%- Primary cases

• 0.9% to 27.2%- Persistent/ recurrent cases

INVESTIGATIONS

ULTRASOUND AND COLOR DOPPLER

Ultrasound• Discrete oval nodules that

are homogeneously hypoechoic relative to the thyroid gland

• Discrete from adjacent thyroid gland- echogenic thyroid capsule may be visible separating them

Color Doppler• Prominent feeding artery (a

branch of superior or inferior thyroid artery) that courses along the periphery of the gland before penetrating deeper at one of the poles of leading to a vascular arc

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Sensitivity: 86%, specificity: 100%

USG IN DETECTION OF INTRA THYROIDAL PARATHYROID ADENOMA

MIBI SCAN

Tc99m MIBI Scan• Early-phase uptake- Hyper/ Iso intense

within abnormal parathyroid- focus of activity separate from the thyroid gland/ a bulge or asymmetry of the thyroid contour can help

• Late phase uptake- Differential washout of radiotracer, with retention of contrast in parathyroid tissue

False positive studies

• Thyroid adenoma/ carcinoma/ Hürthle cell lesion• Multinodular goiter• Reactive lymph node• Ectopic thyroid tissue• Thymus, brown fat

MIBI Scan

• 81% sensitivity for ectopic adenomas

• 82% in general

- Castellani et al. Role of Tc-99m sestamibi scintigraphy in the diagnosis and surgical decision making process in primary hyperparathyroid disease. Clin Nucl Med 2001;26:139-144

- Erbil et al. Impact of Adenoma Weight and Ectopic Location of Parathyroid Adenoma on Localization Study Results. World J Surg 2008;32:566-571

SPECT CT

• Sestamibi SPECT CT- Improves localization of ectopic tumors

FNAC• Easily confused with thyroid due to overlap

in cytomorphologic features of the aspirated cells

• No single cytomorphologic feature is diagnostic

• A combination raises the possibility of a parathyroid lesion

• Immunostaining for PTH on destained Pap smears or cell block sections can confirm a lesion's parathyroid origin

Haytham et al. Ultrasound guided fine needle aspiration biopsy of parathyroid gland and lesions. Cyto Journal 2006

Parathyroid hormone assay in needle aspirates

• PTH assay using needle aspirates

• Should be performed only if localization of the adenoma is missed by non-invasive study

Marcocci et al. Preoperative localization of suspicious parathyroid adenomas by assay of parathyroid hormone in needle aspirates. Eur J Endocrinology 1998;139:72-77

Marcocci et al. Preoperative localization of suspicious parathyroid adenomas by assay of parathyroid hormone in needle aspirates. Eur J Endocrinology 1998;139:72-77

OTHER MODALITIES

CECT• An avidly enhancing soft

tissue nodule in a characteristic location in a patient with primary hyperparathyroidism should raise the index of suspicion

• Sensitivity- 46% to 87%.• Studies that have

combined sonography and CT for preoperative localization purposes show only a small improvement in sensitivity over ultrasonography

• The MR signal characteristics of parathyroid tissue vary depending on the histology of the gland

• Mostly adenomas are T2 hyperintense and T1 iso- to hypointense relative to skeletal muscle

• D/D- lymph node

MRI

Operative approach

no

Thyroidectomy

nono

yes

Intraoperative Ultrasound

Norton et al. Intraoperative Ultrasound and Reoperative Parathyroid Surgery: An Initial Evaluation. World J Surg 1986;10:631-639

Intraoperative Frozen Section

Typical adenoma Oncocytoma

Sources of error

• Frozen section artifact, sampling error, judgmental error contributed to deferred or incorrect diagnoses

• The coexistence of parathyroid and nodular thyroid disease- Intrathyroidal parathyroid glands showing conspicuous follicle formations or abundant oncocytic cells and thyroid nodules with fatty stroma

Additional pathological features

• Examination for oxalate crystals

• Argyrophilia

• Electron microscopy for secretary granules

• Immunohistochemistry for thyroglobulin

PERSISTENT PHPT

Persistent PHPT-Sites of ectopic glands

• Tracheo esophageal groove (27%)• Thymus (17%)• Intrathyroidal (10%)• Undescended glands (8.6%)• Carotid sheath (3.6%)• Retroesophageal space (3.2%)

Jaskowiak N et al. A Prospective Trial Evaluating a Standard Approach to Reoperation for Missed Parathyroid Adenoma. Ann Surg 224:308-322

Investigations in persistent cases

Investigation True positive% False positive%

USG 48 21

MIBI scan 67 0

CT 52 16

MRI 48 14

FNAC for PTH 69 0

Angiography 59 9

Venous sampling 76 4

Management approach

Non invasive studies- USG, MIBI, CT, MRI

ASPIRATION ANGIOGRAPHY VENOUS SAMPLING

SURGICAL EXPLORATION

2 or more positives

negative

neg neg

Yes

Take home message

• Rare entity

• High degree of suspicion pre- and intra-operatively

• Careful search for ectopic locations in suspicious cases

• Intraoperative ultrasound, FNA for PTH aspirate, frozen- useful adjuncts

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