Medullary Thyroid Carcinoma and Pheochromoeytoma Accompanied with Nodular Hyperplasia in Multiple Endocrine Neoplasia Type 2* Takao OBARA,Yoshihide FUJIMOTO, Atsushi OKA, Masayuki FUKUMITSU, Kaoru ABE, KazuyoshiYAMAGUCHI and Tatsuo WADA A B S T R A C T : Three patients with familial multiple endocrine neoplasia type 2 underwent total adrenalectomy and subsequently near-total or total thyroidectomy. The overt pheochromocytomas were present bilaterally in two patients and unilaterally in another patient. In addition, multiple nodules measuring a few mm in diameter were demonstrated in all adrenal medullas examined. AlI patients exhibited bilateral medullary thyroid carcinomas which varied in size from a few minute nodules accompanied by the microscopic C-cell hyperplasia to distinct large tumors. The thyroid C-cell hyperplasia appeared to be confined to the upper and middle thirds of the lateral lobe, and micronodules of the C-cell hyperplasia enlarged to coalesce, forming one large carcinoma mass. On the other hand, nodular hyperplasia of the chromaffin cells was distributed diffusely throughout the adrenal medulla and each nodule appeared to develop individually into a large pheochromocytorna. These findings suggested that, at least in the family members at a high risk for multiple endocrine neoplasia type 2, the development of both medullary thyroid carcinoma and pheochromocytoma was always preceded by a multicentric nodular hyperplasia. On the basis of the pathogenesis of these tumors, the most rational surgical approach was presented. KEY W O R D S : Multiple endocrine neoplasia type 2, medullary thyroid carcinoma, pheochromocytorna, calcitonin, catecholamine. I NTRODUCTION C a s e s of medullary thyroid carcinoma associated with pheochromocytoma and parathyroid tumors (multiple endocrine neoplasia type 2) have been accumulating since Sipple described it as a distinct clinicopathological entity in 1961 (Sipple's syndrome). 9 This syndrome is clustered within a family and transmitted in an autosomal dominant trait with a high penetrance. The tumors in the thyroid and adrenals were often bilateral, v Medullary thyroid carcinoma is generally thought to be derived from the parafollicular cell (Ccell) and secretes calcitonin. The introduction ofradioimmunoassay to measure the serum calcitonin level has facilitated early recognition of patients in high risk families, even before the clinical manifestation of the thyroid involvement becomes evident. 6,s Recently much attention has been focused on the mode of development of medullary carcinoma and From the Institute of Clinical Medicine, Universily of Tsukuba, Ibaragi ; the Second Department of Surgery, University of Tokyo; Endocrine Division, National Cancer Center Research Institute; and the Department of Pathology, the University of Tokyo, Tokyo, Japan. *Presented at the 141h Annual Congress of the Japan Societyfor Cancer Therapy, Sendai, September 30, 1976. JAPANESEJOURNAL OF SURGERY,VOL. 7, No. 4, pp. 235-245, 1977
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pheochromocytoma in the familial form of multiple endocrine neoplasia type 2. Cases with a slight but significantly high concentration of serum calcitonin and multiple foci of C-cell hyperplasia without tumor formation have been reported, which might represent an early form of medullary thyroid carcinoma. 14 O n the other hand, Carney and his associates 8 documented a case of bilateral hyperplasia of the adrenal medulla indicative of the precursor of pheochromocytoma in patients with bilateral multicentric medullary thyroid carcinoma. We have experienced three cases of familial multiple endocrine neoplasia type 2. In all patients, bilateral multi-nodular proliferations were demonstrated in the adrenal medullae in addition to macroscopically overt pheochromocytomas, and medullary thyroid carcinomas were found bilaterally, varying in size from multiple small nodules to distinct large tumors. The purpose of the present report is to describe the pathological findings observed in these cases that would help clarify the mode of development of multiglandular abnormalities in multiple endocrine neoplasia type 2. The understanding of the pathology is important in the planning the rational surgical approach to the disease. MATERIALS AND METItODS
Three patients with a familial form of multiple endocrine neoplasia type 2 (MEN type 2) admitted to the University of Tokyo Hospital between January, 1974 and April, 1975 were included in this study. Cases 1 and 2 were siblings. Case 3 was from another kindred. T h e reseeted specimens of thyroid glands of Cases 1 and 3 were sectioned in a frontal plane, while in Case 2 cross sections at a thickness of 2-4 m m were made in a plane perpendicular to the long axis of the lateral lobes and the isthmus was sectioned in a sagital plane. In Case 2, alternate sections were taken at various levels for determination of the calcitonin content. Tissues for histological study were fixed in 10 per cent buffered formalin solution and processed in usual manner. Microscopic slides of the thyroid and parathyroid tissues were stained with hematoxylin and eosin; congo red for demonstrating amyloid; and Grimelius silver stain for argyrophilic granules. In addition, immunoperoxidase staining was performed on the slides from Case 2, using the technique described by Wolfe and his co-workers. 14 The adrenal tissues were sectioned at 2-4 m m thickness in a plane perpendicular to their long axis and embedded in paraffin. Sections obtained from each block were stained with hematoxylin and eosin, and PAS methenamine silver. Plasma calcitonin levels were determined by the radioimmunoassay using rabbit antisera, raised against synthetic calcitonin M. The details of the method were reported elsewhere.I In the normal subjects, the plasma level of calcitonin (hCT) was less than 0.05 ng/ml. Plasma parathyroid hormone (PTH) levels were determined by the radioimmunoassay as reported previously, lz Normal value is less than 0.5 ng/ml. RESULTS
Clinical Observation Case 1: Ha. M., a 24-year-old female presented a 2 cm nodule in the left thyroid lobe and marked lymph node enlargement in the left side of the neck. A chest X-ray showed a right upper mediastinal lymphadenopathy. A possibility of medullary thyroid carcinoma was strongly suggested on the basis of physical and roentgenologic findings characteristic for this type of thyroid carcinoma. 5 The increased urinary catecholamine excretion was found. In the further studies the presence ofpheochromocytomas was confirmed, though
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they had been clinically silent. Bilateral total adrenalectomy was performed via transabdominal approach. At laparotomy, three minute nodules were found on the surface of the liver, biopsy of which revealed metastases from medullary carcinoma of the thyroid. One month later, near--total thyroidectomy associated with cervical and mediastinal dissection of lymph nodes were performed. The enlarged right superior parathyroid gland was removed, and the left superior parathyroid gland, which appeared to be normal was also biopsied. The plasma before the operation was kept frozen until the assay o f h C T and P T H was feasible. The P T H level was 1.25 ng/ml, and the plasma hCT was 22.4 ng/ml. The plasma h C T level declined to 0.45 ng/ml after the operation. Case 2: Hi. M., a 22-year-old male, a brother of Case 1, gave a past history of an episode of paroxysmal hypertension at the age of 17. The chemical analysis of 24-hour urine specimens showed that the contents of both epinephrine and norepinephrine were markedly elevated. Six months later, the patient developed another attack of hypertension which lasted for 20 hours. On admission, blood pressure was 120/70 and pulse rate was 72. There were no palpable thyroid nodule or cervical lymphadenopathy and no palpable abdominal mass. The basal plasma h C T was 0.07 ng/ml. A four hour infusion of calcium (10 mg/kg of body weight) produced a significant rise in plasma h C T level up to 0.165 ng/ml indicating the presence of medullary thyroid carcinoma, because in normal individuals the maximum value was less than 0.1 ng/ml. Bilateral total adrenalectomy was carried out. One month later total thyroidectomy was done along with bilateral modified neck dissection. No abnormal parathyroid glands were found and a biopsy of one gland was also normal. The patient has been well, taking hydrocortisone and desiccated thyroid daily. The plasma h C T has remained normal. Case 3: K. S., a 30-year-old male was admitted with a thyroid nodule of two year's duration. This patient belonged to another kindred. Two elder sisters had medullary Table 1. The clinical and roentgenological findings in three cases of multiple endocrine neoplasia type 2
Age Sex Initial manifestation Past history Familial history
Thyroid nodule Cervical lymphadenopathy Blood pressure Pulse rate Soft tissue roentgenogram of the neck Nephrotomogram
Case 1
Case 2
Case 3
24
22
30
female
male
A left thyroid nodule and cervical lymphadenopathy none
An episode of paroxysmal hypertension
an episode of paroxysmal hypertension at the age of 17 Siblings Paternal grandfather and father died of acute cardiac failure, at the age of 35 and 32, respectively.
male A right thyroid nodule Urolithiasis at the age of 29 Maternal grandmother had a thyroid nodule. Two elder sisters had bilateral medullary thyroid carcinoma a 2.5 • 3 cm, right moderate
a 2 • 3 cm, left marked
not palpable none
112/70 76 coarse and psammomatous calcification bilateral tumor shadows
120/70 72 no calcification
130/84 72 coarse and psammomatous calcification
a left tumor shadow
normal
Laboratory data of three cases of multiple endocrine neoplasia type 2
T a b l e . 2.
Serum chemistry Total protein (g/100 ml) Albumin (g/100 ml) Calcium (mg/100 ml) Phosphorus (mg/100 ml) Alkaline phosphatase (KA unit) Plasma calcitonin (ng/ml) Basal After calcium infusion Plasma PTH (ng/ml) Urinary catecholamine VMA (mg/24-hours) Epinephrine (mcg/24-hours) Norepinephrine (mcg/24-hours) Metanephrine (mcg/24-hours) Normetanephrine (mcg/24-hours) T a b l e 3.
Case 1
Case 2
Case 3
7.14 4.38 8.97 3.36 7.5
7.46 4.34 9.48 4.02 7.6
8.2 4.2 9.2 3.5 5.7
22.4 -1.2
0.07 0.165 less than 0.3
3.4 300 less than 0.3
-81.7-172.8 40.8 ---
negative 141.4-282.2 155.6-185.1 ---
7.6-9.1 32.9 88.6 74.5-108.6 0.28-0.32 0.38-0.53
Pathological findings in the cases of multiple endocrine neoplasia type 2 Case 1
Medullary thyroid carcinoma
Metastasis of medullary thyroid carcinoma Parathyroid
Adrenal medulla Right
Left
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Case 2
Case 3
Bilateral Bilateral 3• cm and 0.7• 1 mm in diameter with mm (left). Multiple foci of C-cell prolifersmall nodules up to 4 ation (both lobes) mm (right) Cercival and mediastinal None lymph nodes and liver
Bilateral 4 • 4 cm (right) and 1.5 • 1.5 cm (left)
A chief cell adenoma (right superior), Biopsy of one gland
Biopsy of one gland normal
Biopsy of one gland normal
2 pheochromocytomas (15 g and 13 g) and nodular hyperplasia 2 pheochromocytomas (78 g in total) and nodular hyperplasia
Nodular hyperplasla
1 pheochromocytoma (0.7 cm in dia.) and nodular hyperplasia 1 pheochromocytoma (1 cm in dia.) and nodular hyperplasia
1 pheochromocytoma (34 g) and nodular hyperplasia
Cervical lymph nodes
t h y r o i d c a r c i n o m a a n d u n d e r w e n t t h y r o i d operations 16 a n d 15 years previously. Past history i n d i c a t e d t h a t he h a d occasional episodes of p a l p i t a t i o n u n r e l a t e d to either exe r t i o n a l or e m o t i o n a l stress. O n physical e x a m i n a t i o n , b l o o d pressure was 130/84 a n d pulse r a t e 72. T h e p l a s m a basal level of h C T was 3.4 n g / m l a n d m a r k e d l y increased u p to 300 n g / m l after c a l c i u m infusion (4.5 m g / k g in 10 min.). T h e u r i n a r y c h e m i c a l a n a l y sis showed e l e v a t e d c a t e c h o l a m i n e excretions. I n spite of the negative findings of n e p h r o t o m o g r a m , these l a b o r a t o r y d a t a p r o v i d e d the necessity of a b d o m i n a l e x p l o r a t i o n for p h e o c h r o m o c y t o m a s p r i o r to t h y r o i d e c t o m y . A t l a p a r o t o m y , small p h e o c h r o m o c y t o m a s were f o u n d in b o t h a d r e n a l glands. Bilateral total a d r e n a l e c t o m y was performed. T h r e e
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months later, total thyroidectomy associated with a dissection of bilateral cervical lymph nodes was carried out. The left superior parathyroid gland was biopsied and found to be normal. Other parathyroid glands were not identified. The plasma h C T has been at the normal level after thyroidectomy.
R ~ X ,
~
0
L ~ 2 X 3 e m
.
7 • Case 1
0.1•
0'1• Case2
4
•
1'5•
Case 3 Fig. 1. Schematic localization of medullary thyroid carcinoma in three cases. In all cases, nodules were located in the upper and middle thirds of the lateral lobes bilaterally. While in Case 1 an additional lesion was encountered in the lower third of the left lobe, which seemed to represent the intraglandular metastasis.
Fig.2.
Section of the thyroid from Case 2. Note minute nodules of medullary carcinoma with amyloid and calcification (A and B) and proliferation of the parafollicular cells (C-cell) (arrows). Hematoxylin and eosin, • 7,
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T h e details of clinical a n d l a b o r a t o r y findings are given in T a b l e s 1 a n d 2.
Pathological Findings T h e p a t h o l o g i c a l findings of the thyroid, a d r e n a l a n d p a r a t h y r o i d in these cases o b t a i n e d at o p e r a t i o n were s u m m e r i z e d in T a b l e 3. Thyroid: I n all cases, macroscopically, the t u m o r nodules o f v a r y i n g size r a n g i n g from 1 m m to 4 c m in d i a m e t e r were f o u n d in the u p p e r a n d m i d d l e thirds of the l a t e r a l lobe bilaterally, while in Case 1 a n a d d i t i o n a l n o d u l e was e n c o u n t e r e d in the lower t h i r d of the
Fig. 3.
Section of medullary thyroid carcinoma from Case 1. Note sheets of tumor cells divided by fibrous septa and normal thyroid follicles remained between them. Hematoxylin and eosin, x 35.
Fig. 4.
Section of medullary thyroid carcinoma from Case 3. Note two different compartments; a nest of polyhedral cells with solid alveolar arrangement (right) and spindle cells with perivascular arrangement (left), bound with each other. Hematoxylin and eosin, x 70.
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Fig. 5.
Multiple slices through the right adrenal from Case 2. Note multinodular proliferation in the medulla.
Fig. 6.
Figurative reconstruction of distribution of intramedullary nodular hyperplasia on multiple sliced of the adrenals in three cases (light shaded area). Dark shaded areas showed overt pheochromoeytomas. Note no predilection of nodules in the particular region of the adrenal.
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left lobe (Fig. 1). Histology in Case 2 showed that clusters of polyhedral cells with granular acidophilic cytolplasm were stained with hematoxylin and eosin adjacent to the minute nodules (Fig. 2). Immunoperoxidase staining confirmed the proliferation of calcitonin-positive cells, predominantly in the upper third of the both lateral lobes in Case 2. In the upper part of the right lobe in Case 1, there were multiple small nodules. The histology of the large nodules in Cases 1 and 3 showed lobular architecture divided by fibrous septa and clusters of a few thyroid follicles inbetween (Fig. 3). The cancer nodule of the left lobe of Case 3 consisted of two parts; a nest of polyhedral cells with solid-alveolar arrangement and that of spindle cells with perivascular arrangement, both were bound with each other (Fig. 4). The Grimelius silver stain demonstrated argyrophilic intracytoplasmic granules in a portion of tumor cells in all cases. The amyloid was stained with congo red and it showed the presence of green birefringense in polarized light in all three cases. Metastases to the cervical lymph nodes were identified by histology in Cases 1 and 3, but was most extensive in Case I, involving the mediastinal lymph nodes. Adrenal: Grossly, multiple bilateral pheochromocytomas were found in Case 1. The size of the tumors ranged from 1 to 7 cm in diameter and three large tumors weighed 13, 15, and 78 g, respectively. In Case 3, also, adrenal tumors were bilateral, 0.7 and 1 cm in diameter each. In Case 2, an unilateral pheochromocytoma weighing 34 g was found in the left adrenal. The right adrenal gland appeared normal. Serial blocks examined at interval of 2 to 4 mm, however, disclosed multiple nodular proliferation of the medullary tissue ranging from 0.5 to 5 m m in diameter (Fig. 5). On further histological examination of the adrenal tissues in Cases 1 and 3 which appeared grossly normal, a number of tiny intramedullary nodules ranging from 0.5 to 4 m m were found. These nodular proliferations were encountered in the different parts of the adrenal medulla and showed no predilection for any particular region (Fig. 6). Microscopically, these hyperplastic nodules fused imperceptibly with those of the adjacent apparently normal medulla (Figs. 7 and 8). The cytoplasmic appearance of the nodular hyperplastic cells resembled normal medullary cells, while the tumor cells were larger than those of normal adrenal medulla
Fig. 7.
Section of nodular proliferation in the adrenal medulla. PAS methenamine silver, x 5.
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Fig. 8.
Higher magnification of Fig. 7. The normal adrenal medullary cells are on the left, imperceptibly separated from the tumor cells on the right. Hematoxylin and eosin, x 70.
Fig. 9.
A nodular proliferation with light and dark cells. The cells with dark granular cytoplasm tend to have pyknotic and bizarre nuclei.
243
a n d showed more pleomorphism. T h e prevailing cells in most nodules showed polyhedral configuration with either fine-light or coarse-dark basophilic granular cytoplasm and twisted cord-like arrangement. Those with coarse granules tended to have pyknotic a n d bizarre nuclei (Fig. 9). Parathyroid: I n Case 1, a right superior parathyroid t u m o r was removed. Histology revealed it was a chief cell a d e n o m a . All biopsies of parathyroid gland obtained in Cases 2 and 3 were normal.
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DISCUSSION
The three cases, presented here, apparently belonged to the familial form of multiple endocrine neoplasia type 2 (Sipple's syndrome). O u r experience confirmed the findings of others that the plasma calcitonin level was a very sensitive indicator for the presence of medullary thyroid carcinoma and an enhanced response to the calcium infusion could facilitate early recongition of the clinically occult carcinoma in the members of affected families. 6,8,14 We observed the very early stage of development of medullary thyroid carcinoma in Case 2, in which minute nodules of t m m or less in diameter were accompanied by C-cell hyperplasia. The histology in our cases showed that the familial form of medullary carcinoma is characterized by the bilateral involvement of the thyroid gland and the lesions arose predominantly in the upper and middle thirds of the lateral lobes. 14 The nodules in the right lobe of Case 1 and those in both lobes of Case 2 demonstrated the evidence of multicentric occurrence of medullary carcinoma. Moreover, the section of the large thyroid carcinoma showed that the tumor was composed of two or three compartments, each having different tumor cell cytology and cell arrangement. Between the neighboring compartments, there were small amount of definitely normal thyroid tissue remnant. All these findings suggest that minute nodules originated multifocally from Ccell hyperplasia grow and coalesce to form a large tumor. The nodule in the lower third of the left lobe in Case 1 could be intra-grandular metastasis rather than multicentric occurrence of the carcinoma, in view of the aggressive lymphatic and hematogenous metastasis as evidenced by extensive bilateral involvement of cervical lymph nodes as well as metastasis to the liver. These mode of spread clearly indicates the necessity of total thyroidectomy in patients with the familial form of medullary thyroid carcinoma, even when an unilateral tumor is felt clinically. I f these patients with an unilateral thyroid nodule undergoes subtotal thyroidectomy, the occult lesions in the residual upper part of the opposite thyroid lobe would grow later and the second operation would be necessitated. Pheochromocytomas occurring in patients of multiple endocrine neoplasia type 2 were bilateral in by far higher percentages compared to sporadic cases. 7 In the cases described here, only a single large pheochromocytoma was found in the left adrenal in Case 2, while there were bilateral grossly noticeable pheochromocytomas in the other two cases. It is noteworthy that multiple sections of the seemingly normal right adrenal of Case 2 revealed multiple tiny intramedullary nodules. Further examination disclosed similar findings in the " n o r m a l " remnant part of both adrenals in Case 1, which had not been histologically examined initially. In Case 3, bilateral nodular hyperplasia of the adrenal glands was confirmed. The occurrence of multicentric nodular enlargement of the adrenal medulla had not been generally mentioned in more than 200 cases reported previously. To our knowledge, Dyson 4 reported a case of Cushing's disease associated with a carcinoma of the thyroid, showing nodular proliferation of the adrenal medulla bilaterally. The author described the thyroid lesion as undifferenciated carcinoma, but later Williams et al. 13 revised it as medullary thyroid carcinoma. Sjoerdosma and his associates 11 documented the same findings in patients with familial pheochromoeytoma including those with Sipple's syndrome. Recently Beaugie et al. 2 also described the cases of familial Sipple's syndrome in this regard. As to the mode of development of pheochromocytoma in multiple endocrine neoplasia type 2, Carney and his associates 3 reported a case in which only bilateral diffuse medullary hyperplasia of the adrenal was noted without forming nodules or pheochromocytomas and proposed that diffuse hyperplasia would
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be followed b y m u l t i p l e n o d u l a r e n l a r g e m e n t l e a d i n g to the final manifestation o f pheoc h r o m o c y t o m a . This concept was s u p p o r t e d b y L j u n g b e r g 7 w h o described two cases with u n i l a t e r a l m u l t i n o d u l a r e n l a r g e m e n t of the a d r e n a l m e d u l l a . O u r cases give further evidence to s u p p o r t this view. N o d u l a r e n l a r g e m e n t of the a d r e n a l m e d u l l a d i s t r i b u t e d diffusely in the a d r e n a l g l a n d a n d no predilection was n o t e d in the p a r t i c u l a r region. T o t a l a d r e n a l e c t o m y , therefore, m a y offer b e t t e r c h a n c e for cure. W e took this policy in o u r cases. However, controversy still exists in this respect. S h i m a a n d his associates t0 s t a t e d t h a t r e m o v a l o f m a c r o s c o p i c a l p h e o c h r o m o c y t o m a s was the t r e a t m e n t o f choice r a t h e r t h a n total a d r e n a l e c t o m y , because almost all p h e o c h r o m o c y t o m a s in Sipple's synd r o m e were benign a n d it usually took m o r e t h a n I0 years until these tiny nodules m i g h t develop to the clinically manifest disease, while patients could a v o i d the s u p p l e m e n t thera p y o f corticosteroid. I n a p a t i e n t with m e d u l l a r y t h y r o i d c a r c i n o m a , it is m a n d a t o r y to rule out the possible association of p h e o c h r o m o c y t o m a , because t h y r o i d e c t o m y p e r f o r m e d on patients with unsuspected p h e o c h r o m o c y t o m a m a y be followed b y a fatal outcome. M o r e o v e r , it is necessary to follow patients for m a n y years who were o p e r a t e d for m e d u l l a r y t h y r o i d c a r c i n o m a alone or along with u n i l a t e r a l a d r e n a l lesion for the d e v e l o p m e n t o f other p h e o c h r o m o c y t o m a s w h i c h m a y occur later in life. (Received for publication on April 4, 1977)
References 1. Abe, K. and Adachi, I.: Radioimmunoassay of human calcitonin and clinical assessment, Naika (Internal Medicine) 37: 299-304, 1976. (in Japanese) 2. Beaugie, J.M., Belchetz, P.E., Brown, C.L., Frankel, R.J. and Lloyd, M.H. : Report of a family with inherited medullary carcinoma of the thyroid and pheochronmcytoma, Brit. J. Surg. 62: 264-268, 1975. 3. Carney, J.A., Sizemore, G.W. and Tyce, G.W. : Bilateral adrenal medullary hyperplasia in multiple endocrine neoplasia, type 2--The precursor of bilateral pheoehromocytoma, Mayo Clin. Proc. 50: 3-10, 1975. 4. Dyson, B.C. : Cushing's disease--Report of a case associated with carcinoma of the thyroid gland and cryptococcosis, New Engl. J. Med. 261: 169-172, 1959. 5. Fujimoto, Y., Oka, A., Fukumitsu, M., Obara, T., Akisada, M. and Yamaguchi, K.: Physical and radiological findings specific medullary carcinoma of the thyroid gland, Endocrinol. Japon. 22: 225-232, 1975. 6. Jackson, C.E., Tashjian, A.H. and Block, M.A. : Detection of medullary thyroid cancer by caleitonin assay in families, Ann. Int. Med. 78: 845452, 1973. 7. Ljungberg, O. : On medullary carcinoma of the thyroid, Acta Path. Microbiol. Scand. [A] Supp. 231: 1-57, 1972. 8. Melvin, K.E.W., Miller, H.H. and Tashjian, A.H.: Early diagnosis of medullary car-
cinoma of the thyroid gland by means of calcitonin assay, New Engl. J. .IVied. 285: 1115-1120, 1973. 9. Sipple, J.H. : The association of pheochromocytoma with carcinoma of the thyroid gland, Amer. J. Med. 31: 163-166, 1961. 10. Shima, M., Watanabe, H., Igarashi, D., Tanahashi, Y., Harada, K., Sato, T. and Kobayashi, K.: Six cases of Sipple's syndrome, Shindan-to-Chiryo (Diagnosis and Therapy),
62: 1059-1068, 1974. (in Japanese) 11. Sjoerdosma, A, Engelman, K., Waldman, T.A., Cooperman, L.H. and Hammond, W., G.: Pheochromocytoma: Current concepts of diagnosis and treatment, Ann. Int. ivied. 65: 1302-1326, 1966. 12. Tanaka, M., Abe, K., Adachi, I., Miyakawa, S. and Kumaoka, S. : Radioimmunoassay of parathyroid hormone in human plasma and tissue using commercially available antiserum and modified iodination, Endocrinol. Japon. 21 : 173-178, 1974. 13. Williams, E.D., Morales, A.E. and Horn, R.C.: Thyroid carcinoma and Cushing's syndrome, J. Clin. Path. 21 : 129-135, 1968. 14. Wolfe, H.J., Melvin, K.E.W., Cervi-Skinner, S.J., AI Saadi, A.A., Juliar, J.F., Jackson, E. and Tashjian, A.H., Jr.: C-cell hyperplasia preceding medullary thyroid carcinoma, New Engl. J. Med. 289: 437-441, 1973.
