True posterior mediastinal goiter

TRUE POSTERIOR MEDIASTINAL GOITER* NATHAN

N.

CROHN, M.D. AND MATHEW

W. KOBAK, M.D.

Chicago, Illinois

A

TRUE posterior mediastina1 goiter was recently treated at MichaeI Reese HospitaI. This rare case demonstrated the

IA

been hospitaIized eIsewhere for treatment of a cervical goiter. A chest roentgenogram had revealed a mediastinal tumor. A cervical thy-

2

IB

FIG. I. A, Postero-anterior roentgenogram showing mass in posterior mediastinum; of same patient. Note deviation of trachea and right main bronchus. FIG. 2. Right lateral barium esophagram showing compression.

REPORT

The femaIe, 1947

chest atory sistent

right lateral roentgenogram

roidectomy had been performed and according to the surgeon the mass in the neck was separate from the mediastinal tumor. Tissue removed at this time was reported as adenomas of the thyroid gIand with invoIutiona1 changes. In September, 1949, radioactive iodineIs studies had been performed at the University of Chicago CIinics. It had been noted2 that there was considerabIe IocaIization of iodine in the neck but iodine uptake couId not be deIineated to the mediastinal mass. 1950, after careful studies the In January, patient was referred for surgery. She complained of dyspnea on exertion and aching upper chest pain. Thyroid tissue couId not be paIpated in her neck. Since the cervica1 thy-

foIIowing unusua1 and not generaIIy realized facts: (I) Radioactive iodine as a diagnostic agent may not identify such a deep-seated mass to be thyroid tissue. (2) A direct transthoracic surgica1 approach is the onIy feasibIe means of removing the tumor because of its intimate reIationship to the great vesseIs of the mediastinum. CASE

B,

patient, a fifty-one year old white dated the onset of her symptoms to beginning with occasiona sharp upper pains. She suffered frequent upper respirinfections with cough and later had per1949, she had hoarseness. In February,

* From the Departments of Surgery, Michael Reese Hospital and Northwestern University Medical School. Chicago, III.

August,

1951

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FIG. 3. Photograph of operative fieId during surgery; hemostat points to junction of azygos vein and superior vena cava. A, superior vena cava; B, superior portion of tumor; c, azygos vein; D, tumor mass beneath azygos and vena cava projects into posterior mediastinum.

roidectomy she had gained 35 pounds and now weighed 335 pounds. The basaI metaboIism was minus 5 per cent. Roentgenographic studies (Fig. IA and B) showed a widening of the mediastinum due to a rather homogeneous, we11 defined non-puIsating tumor. The aortic knob was pushed downward and IateraIIy. The trachea was compressed anteriorIy whiIe barium studies (Fig. 2) showed the esophagus compressed posterioriy. The mass did not move upward with swaIIowing. On January 23, 1950, under intratrachea1 anesthesia a right thoracotomy was performed through the bed of the resected fourth rib. The mass (Fig. 3) Iay on the vertebra1 coIumn and was smooth, firm and fairIy we11 encapsuIated. AnteriorIy and mediaIIy it was attached to the superior vena cava, the trachea and the right main bronchus. AnteriorIy the azygos vein crossed the Iower poIe of the mass transverseIy to join the vena cava. The azygos vein was diIated, stretched and thinned so that its caIiber was about three times normaI. It was intimateIy adherent to the capsuIe of the tumor. These reIationships of the azygos are emphasized because tearing and severe hemorrhage wouId seem inevitabIe unIess the vein were dissected and freed under direct vision. The vein may be preserved as in our case by deIivery of the tumor from beneath it or it may be sacrificed. Subsequent pathoIogic examination showed that the tumor was a Iarge (4 by 5 by 6 cm.)

MediastinaI

Goiter

FIG. 4. Photomicrograph

of removed tumor.

thyroid noduIe with minima1 secondary (Fig. 4.)

changes

COMMENTS

During the past few years a number of author@ have cited cases in which thyroid tissue was found in the “posterior mediastinum.” However, in reviewing these reports it became apparent to us that aImost a11 of the goiters were above the true posterior mediastina1 space. CIarity of definition of the boundaries of this region is of more than academic importance because the bordering vascuIar structures determine one choice of surgica1 approach to goiters actuaIIy within this area. AnatomicaIIy the entire mediastinum lies behind the sternum and extends posteriorIy to the spine. Its IateraI borders are the median pIeura1 reffections which act as curtains separating each side of the thorax. This mediastina1 space is divided transverseIy and verticaIIy for descriptive purposes. The transverse Iine separates the superior from the inferior mediastinum and is a Iine drawn at the IeveI of the bifurcation of the trachea. This Iine is aIso at the same plane as the azygos vein in its entry into the superior vena cava.s It extends between the Iower aspects of the manubrium sterni and the body of the fourth thoracic vertebra. OnIy the inferior mediastinum is divided into an anterior, middIe and posterior portion. The true posterior mediastinum therefore can be said to lie onIy below the IeveI of the fourth thoracic vertebra. It extends downward to the

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diaphragm and Iies on the spine behind the pericardium. A true posterior mediastina1 tumor must lie at Ieast in part within the aforementioned prescribed area. FrequentIy a mass is said to be posterior mediastina1 when it is onIy in the superior mediastinum. The error arises from the fact that the tumor may be posteriorIy pIaced. Even in our case, which was as inferiorly situated as any that we couId find reported, the goiter was only partiaIIy within the true posterior mediastinum. We know of no case of a goitrous mass compIeteIy confined to the true posterior mediastinum. In attempting to expIain how thyroid tissue couId come to Iie in this Iow posterior Iocation we have taken a number of factors into consideration: Explanation Based on Embryologic Factors (Aberrant Thyroid). The main mass of the thyroid is derived from the ventra1 floor of the pharynx at the IeveI of the first pharyngea1 pouches.’ According to WeIIer” this primordium contributes the isthmus of the gIand and a smaI1 portion of each lobe. The uItimobranchia1 bodies apparentIy form a great share of the Iobes of the thyroid and are derived from the fifth pharyngea1 pouch. These bodies fuse with the median mass at the seventh week. The uItimobranchia1 bodies Iie deep within the body of the deveIoping embryo adjacent to the posterior pericardium. It is conceivabIe that failure of f&ion of these bodies with the main thyroid anIage or their actua1 attachment to the pericardium might Ieave thyroid tissue in the deveIoping posterior portions of the mediastinum. This concept is given support by the observation that some vertebrate structures which correspond to human uItimobranchia1 bodies form isoIated suprapericardia1 bodies cIose to the pericardium.3 Explanation Based on “Descent” of the Tbyroid (“Plunging” Goiter). Anatomic Considerations: The thyroid gland in the neck is encIosed by the cervica1 visceral fascia which Iikewise covers the trachea and esophagus.6 This fascia is an extension of the viscera1 fascia of the chest and in our concept may pIay a roIe in directing descent of a thyroid into the posterior mediastina1 areas. Such a descending thyroid wouId undoubtedIy proceed downward more readiIy on the right side than on the Ieft where the aortic arch cIoseIy hugs the vertebra1 column. Pathologic Considerations: UsuaIIy

August, 1951

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when a thyroid enIarges it does so in an anterior direction and in growing or “descending” downward comes to Iie in the anterior portion of the superior mediastinum or in the anterior mediastinum. In other cases in the more rare posterior projection growth of the gIand is directed toward the posterior portion of the superior mediastinum and “descent” from here wouId be toward the true posterior mediastinum.O The use of radioactive iodine may be instrumenta1 in the diagnosis of some intrathoracic thyroids. Touroff lo has stated that in his experience an aImost’ IOO per cent accuracy of diagnosis can be obtained by this means. In our case this method proved faIIibIe. Uptake of iodine’31 was observed in the neck but it was not possibIe to say that the mass in the mediastinum IocaIized the iodine. Many of these tumors are non-functioning coIIoid adenomas or other types of goiter not predisposed to iodine uptake.4 CuriousIy, even morphoIogicaIIy simiIar adjacent foIIicIes containing abundant coIIoid may show marked variation in uptake of radioactive iodine.4 Thus normaIIy functioning thyroid may exist in the neck and a non-functioning adenoma in the chest. In addition with masses cIoseIy associated, as in our case, it may not be possibIe to determine which mass is taking up the iodine.2 FinaIIy a question of bIood suppIy to the thyroid tissue may be a factor of importance in determining uptake.2 In concIusion it wouId appear to us that once the diagnosis of a true posterior mediastina1 goiter has been established the onIy feasibIe surgica1 approach wouId embody transthoracic exposure. This wouId be necessary because of the intimate attachment of the azygos vein to the majority of these tumors. This vein must frequentIy be divided in order to remove the growth. Any procedure through a cervica1 approach aIone wouId run the risk of severe hemorrhage in a deep cavity. The use of an anterior sternum-spIitting incision to reach a tumor pIaced behind the great vesseIs simiIarIy does not appear IogicaI. ControI of the bIood suppIy to the gIand can aIso usuaIIy be accomplished better with the transthoracic technic as in most cases the main vesseIs are derived from the subclavian and inferior thyroid sources within the chest. SUMMARY

An instance of goiter entering the true posterior mediastinum has been presented. This

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case iIIustrated the facts that (I) radioactive iodine as a diagnostic too1 may not disclose the etioIogy of such a mass, and (2) a transthoracic exposure is necessary to remove such a deepIy situated thyroid. REFERENCES

I. AREY, L, B. DeveIopmental Anatomy. Philadelphia, 1940. W. B. Saunders Co. 2. CLARK, D. W. Personal communication to the authors. 3. CUNNINGHAM, D. J. Revised and rewritten by AppIeton, A. B. Ductless, Glands. In: Cunningham’s Textbook of Anatomy. New York, 1937. Oxford University Press. 4. FITZGERALD, P. J., FOOTE, F. W. and HILL, R. F.

5. 6. 7.

8.

g.

IO.

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Concentration of Ii*, in thyroid cancer as shown by radioautography. Can&, 3: 86-105, 1950. GRAY, H. Edited by Goss, C. M. Gray’s Anatomy, p. 676. PhiIadeIphia, 1948. Lea & Febiger. Ibid., p. 370. KEYNES, G. Thyroid surgery fifty years ago with a contribution on intrathoracic noitre. &it. M. J.. I : 621-626, 1950. MORA, J. M., ISAACS, H. J., SPENCER, S. H. and EDIDIN, L. Posterior media&ml goiter. Surg., Gynec. @? Obst., 79: 314-317, 1944. SWEET, R. H. Intrathoracic goiter located in the posterior mediastinum. Surg., Gynec. TV Obst., 89: 57-66, 1949. TOUROFF, A. S. W. In discussion of Adams, H. D. Transthoracic Thyroidectomy. J. Tboracic Sup.,

19: 741-754. 1950. I I. WELLER. Quoted by Cunningham, D. J. Revised and rewritten by AppIeton, A. B.8

IN treating hernias instead of using fascia Iata or prepared beef fascia one can use cutis grafts (skin with the epidermis removed) or whoIe skin grafts. ZavaIta et a1. have used whoIe skin in aImost 300 cases of hernia (primary or recurrent, inguinal, femora1, nava1 or incisional) with exceIlent results. So Iong as the grafts of ful1 thickness skin are cIeared of fat tabs and are sutured tautIy the incidence of infection remains very Iow and ex&IIent resuIts are obtained. Besides, it is a convenient procedure because the skin can be taken from the margin of the hernial incision, hence two scars are unnecessary. (Richard A. Leonardo, M.D.)

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