© 2013 Wiley Periodicals, Inc.
155
REVIEW ARTICLE _______________________________________________________________
Intracardiac Ectopic Thyroid (Struma Cordis) Josef Besik, M.D., Ph.D.,* Ondrej Szarszoi, M.D., Ph.D.,* Anastazie Bartonova, M.D.,y Ivan Netuka, M.D., Ph.D.,*,z Jiri Maly, M.D., Ph.D.,* Marian Urban, M.D.,* Jozef Jakabcin, M.D., Ph.D.,§ and Jan Pirk, M.D., Ph.D.* *Department of Cardiac Surgery, Institute for Clinical and Experimental Medicine, Prague, Czech Republic; yDepartment of Pathology, Institute for Clinical and Experimental Medicine, Prague, Czech Republic; z2nd Department of Surgery, Department of Cardiovascular Surgery, First Faculty of Medicine, Charles University in Prague, Prague, Czech Republic; and §Department of Cardiology, Masaryk Hospital, Usti nad Labem, Czech Republic ABSTRACT A 67-year-old male with a history of gastrointestinal malignancy was found to have a tumor in the right ventricular outflow tract. The tumor was surgically removed, and the histological diagnosis was thyroid struma. We review the literature on this rare cardiac tumor. doi: 10.1111/jocs.12245 (J Card Surg
2014;29:155–158)
Intracardiac ectopic thyroid (struma cordis) is a rare cardiac neoplasm. The first case of ectopic thyroid tissue in the right ventricular cavity was made during a routine autopsy by Dosch in 1941.1 The first successful surgical removal of an intracardiac goiter was documented by Lo et al. in 1984.2 Worldwide, 33 case reports have been published to date (Table 1), including a case of adenoma and invasive follicular carcinoma.3,4 PATIENT PROFILE A 67-year-old male was admitted with dyspnea on exertion (New York Heart Association functional class II [NYHA II]) 10 months following a sigmoid colon resection for adenocarcinoma found in a polyp (cancer stage T1N0M0). Transesophageal echocardiography showed an oval mass 30 mm 27 mm 24 mm in size, ‘‘gelatinous’’ in character with small cavities, broadly attached to the interventricular septum in the region of the right ventricular outflow tract (RVOT) (Fig. 1). The function of both ventricles as well as all heart valves was normal. Due to suspected adenocarcinoma metastasis, magnetic resonance imaging (MRI) (Fig. 2) and positron emission tomography/computed tomography (PET/CT) examinations were also performed. In both procedures, the tumor showed low contrast medium (glucose) saturation, which Conflict of interest: The authors acknowledge no conflict of interest in the submission. Address for correspondence: Josef Besik, M.D., Ph.D., Department of Cardiac Surgery, Institute for Clinical and Experimental Medicine, Prague, Czech Republic. Fax: 00420236052776; e-mail: [email protected]
provided evidence that it was benign in nature. Tumor marker levels (alpha-1-fetoprotein, CA 72-4, CA 19-9, CEA, PSA) were within normal ranges, as were other laboratory values, including thyroid hormone levels. Abdominal sonography revealed no pathological findings. A coronary angiography showed no coronary lesion. After performing a median sternotomy, extracorporal circulation was established with bicaval cannulation and the heart was arrested with cold blood cardioplegia. After accessing the right ventricle through the right atrium and tricuspid valve, a broadly attached spherical mass 30 mm in diameter with a whitish surface was found in the right ventricular outflow tract (Fig. 3). The mass had an elastic consistency, was well-differentiated from the surrounding tissue, and showed no evidence of invasion. The tumor was excised and sent to histology for examination. The histology was composed of thyroid tissue showing features of a colloid goiter. An immunohistochemical examination using anti-thyroglobulin antibodies and TTF 1 was positive. Proliferation marker Ki-67 showed positivity in about 1% of cells. Significant cellular and nuclear atypia and mitosis were not present. The margins were free of tumor (Fig. 4). The patient tolerated the procedure well, and a predischarge transthoracic echocardiography showed no pathological findings and the function of both ventricles and the valves were normal. Three months after surgery the patient feels very well and his dyspnea resolved. He has normal thyroid function. Ultrasonography showed the thyroid in the normal position and somewhat enlarged with micronodular remodeling, not requiring any intervention at present.
156
BESIK, ET AL. INTRACARDIAC ECTOPIC THYROID
J CARD SURG 2014;29:155–158
TABLE 1 Literature Review of Struma Cordis Pat.
Year
Authors
Journal
Gender
Age
Loc.
1 2 3 4 5 6
1941 1963 1982 1984 1985 1986 1986 1986 1987 1988 1988 1988 1988 1989 1990 1993 1993 1993 1995 1994 1995 1995 1995 1996 1997 1997 1999 2000 2000 2002 2003 2005 2006 2009 2009 2011 2011
Dosch1 Rogers and Kesten7 Zorina Lo et al.2 Shemin et al. Kantelip et al. Peycelon et al. Pollice and Caruso8 Grigg et al. Greco-Lucchina et al. Kon et al. Rieser et al.14 Rose et al.9 Doria et al. Richmond et al. Ansani et al.15 Kerlan et al. Polvani et al. Porqueddu et al.10 Maillette et al. Dresler et al. Dresler et al. Castaldo et al. Fujioka et al. Hirnle et al.4 Archundia et al. Pistono et al. Casanova et al.11 Baykut et al. Chosia et al. Larysz et al. Irvine et al.17 Ruberg et al.12 Comajuan et al. Wu et al.3 Fennira et al. Scrofani et al.
Beitr Pathol Anat J Cardiovasc Surg Arkh Patol Am J Cardiol Am J Cardiol Hum Pathol Ann Chir Arch Pathol Lab Med J Am Coll Cardiol Am Heart J Ann Thorac Surg Clin Nucl Med Am J Cardiovasc Pathol Chest Thorax Am Heart J Ann Endocrinol (Paris) Ann Thorac Surg Cardiology Can J Cardiol Dtsch Med Wochenschr Dtsch Med Wochenschr Arch Mal Coeur Vaiss Chest Eur J Cardiothorac Surg Arch Inst Cardiol Mex Cardiologia Ann Thorac Surg Ann Thorac Surg Pol J Pathol Kardiol Pol Interact Cardiovasc Thorac Surg Am J Cardiol Eur J Echocardiogr Interact Cardiovasc Thorac Surg Ann Cardiol Angeiol (Paris) J Cardiovasc Med (Hagerstown)
F F F F F M M F F M F F F F F F F F F F F F F M F F F F F F F F F F F F F
67 51 60 47 58 25 25 59 57 59 56 56 51 66 63 75 51 66 66 63 34 61 43 50 55 33 64 66 42 48 48 46 62 74 33 50 45
RVOT RVOT RVOT RVOT RVOT RVOT RVOT RVOT RVOT RVOT LVOT LVOT RA RVOT RVOT RVOT RVOT RVOT RVOT RVOT RVOT RVOT RVOT RVOT RVOT IVS RVOT RVOT LVOT RVOT RVOT RVOT RVOT RVOT RVOT RVOT RVOT
7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33
F, female; IVS, interventricular septum; LVOT, left ventricular outflow tract; M, male; RA, right atrium; RVOT, right ventricular outflow tract.
DISCUSSION Ectopic thyroid is defined as the finding of isolated thyroid tissue outside of its usual pretracheal location. Ectopia is caused by a disturbance in early embryonic
Figure 1. Two-dimensional transesophageal echocardiography shows an oval mass attached to the interventricular septum in the right ventricular outflow tract (RA, right atrium; RV, right ventricle; AV, aortic valve; T, tumor).
Figure 2. Cardiac magnetic resonance imaging (2D cine tfi sequence) shows a tumor in the RVOT (Ao, aorta; PA, pulmonary artery; T, tumor).
J CARD SURG 2014;29:155–158
Figure 3. Intraoperative photograph shows the tumor (T) in the right ventricle after right atriotomy and retraction of the anterior tricuspid leaflet (not shown).
development. The embryonic thyroid gland begins to develop on approximately the 24th day of gestation as a proliferation of endodermal cells on the base of the primitive pharyngula, at the site of the later foramen caecum linguae, the median anlage. Two lateral anlages and an ultimobranchial body, containing parafolicular cells originating from the neural crest, are formed from the fourth pharyngeal pouch. In this period the thyroid primordium is in close proximity to surrounding structures, including the primitive heart. In subsequent development, the median anlage fuses with the lateral anlage, creating and lengthening what is initially the hollow thyroid diverticulum (later the thyroglossal duct), through which the organ descends to its final location in the neck. The thyroid gland takes its final shape and place in the seventh week of embryonic development. A failure in this descent leads to the ectopic development of all or part of the thyroid gland, which is drawn to another organ or tissue. A failure in the fusion of the medial and lateral anlages then creates a rare lateral goiter, in most cases in the submandibular region.5,6 The overall prevalence of ectopic thyroid is 1 per 300,000 to 400,000; among patients treated and
Figure 4. A histological picture of the excised tumor reveals colloid-filled thyroid tissue with no signs of malignancy (haematoxylin and eosin stain, magnification 100).
BESIK, ET AL. INTRACARDIAC ECTOPIC THYROID
157
monitored for thyroid disease the prevalence is 1 per 4000 to 8000. However, in autopsy studies, prevalence is far greater and reaches up to 10%. Females are affected significantly more often than males. The most frequent form is lingual thyroid (90% of cases). Sublingual placement is less common and includes: suprahyoid and infrahyoid, in the thyroglossal duct, trachea, lungs, mediastinum, aortic arch, or pericardium, including the heart. In extremely rare cases, thyroid tissue is found in the subdiaphragmatic region, such as the gastrointestinal tract, porta hepatis, pancreas, adrenal gland, gall bladder, or urinary bladder.5 The cause seems to be due to aberrant embryonic thyroid tissue migration or heterotopic differentiation of uncommitted endodermal cells. Struma ovarii develops as a part of a monodermal teratoma of the ovary.5 The same pathological processes may develop in ectopic thyroid as in the orthotopic thyroid, including benign and malignant tumors.3,4 Ectopic thyroid in the heart (struma cordis) is a rare finding. Like ectopic tissue in other locations, intracardiac ectopic thyroid arises during embryonic development. It is highly likely that ectopic thyroid is a result of aberrant migration of embryonic thyroid tissue, occurring while the thyroid primordium is in close contact with the embryonic heart, when the posterior part of the primordium is incorporated into the primitive heart.7 The thyroid primordium always comes into contact with the primitive heart at the same site, the bulbus cordis. The outflow tracts of both ventricles are formed from the distal part of the bulbus (infundibulum). The anterolateral part of the infundibulum develops into the right ventricular outflow tract, and the posteromedial part becomes the outflow tract of the left ventricle.8 Only 33 cases of struma cordis have been published worldwide (Table 1). Except for a single finding in the right atrium,9 in every case the ectopic thyroid tissue grew from the interventricular septum and usually spread to the right ventricular outflow tract (29 cases of 33) or, less often, to the left ventricular outflow tract (three cases). Porqueddu et al. suggest that the cause of ectopic thyroid predominantly occurring in the right ventricular outflow tract is most likely due to the persistent contact between the thyroid primordium and anterolateral part of the primitive heart infundibulum, which is the anlage for the development of the right ventricular outflow tract.10 Several authors also mention the possible role of the abnormal migration of neural crest cells.11 The majority of patients are females (30 cases of 33), usually in middle or advanced age. The most common clinical symptoms are varying degrees of shortness of breath after exertion, or sometimes ventricular arrhythmia or pulmonary embolism.12 Some patients are entirely asymptomatic. An echocardiography performed due to cardiac symptomatology or as a routine heart test for an unrelated condition finds a cardiac tumor that is several centimeters in size. The mass almost always originates in the interventricular septum, is usually broadly attached, and protrudes into the right ventricular outflow tract, where it may cause varying degrees of obstruction.
158
BESIK, ET AL. INTRACARDIAC ECTOPIC THYROID
Various types of abnormal masses may occur in the right ventricle—blood clots, benign tumors (usually myxoma, lipoma, papillary fibroelastoma, or rhabdomyoma), malignant primary tumors (sarcoma), and malignant secondary tumors (metastasis).13 When a tumor is found in the right ventricular outflow tract, especially in middle-aged women, intracardiac ectopic thyroid should be considered. If this possibility is suspected, thyroid scintigraphy may be performed to confirm the diagnosis before cardiac surgery.14 We believe it can modify the surgical strategy. Removal of an unknown tumor would be potentially dangerous— there is a risk of iatrogenous interventricular septum injury in case of extensive resection, which is not necessarily needed in cases of struma cordis. Ansani et al. also mention that the right ventricular outflow tract is a frequent site of metastasis. Thyroid carcinoma in particular frequently metastasizes to the heart and it has been suggested that a preoperative thyroid scan might be useful in patients with echocardiogram showing a right ventricular mass partially obstructing the outflow tract.15 If one entertains the possibility of a thyroid nodule within the heart, a neck ultrasound could be useful to identify primary thyroid pathology, such as a follicular tumor that has conceivably metastasized to the heart. Complete removal of struma cordis is usually a safe procedure. Histological diagnosis normally does not represent a problem. It is always very important to rule out the possibility of cardiac metastasis of highly differentiated follicular thyroid cancer.16 It is recommended to perform thyroid function test several weeks after the operation to rule out potential hypothyroidism. No case of thyroidectomy in patients after struma cordis removal was reported. The long-term prognosis for patients is good.17 REFERENCES 1. Dosch F: U¨ber einen Fall von Glandula thyroidea accessoria intracardialis. Beitr Pathol Anat 1941;105: 244–255.
J CARD SURG 2014;29:155–158
2. Lo HM, Tseng YZ, Tseng CD, et al: Intracardiac goiter: A cause of right ventricular outflow tract obstruction and successful operative therapy. Am J Cardiol 1984;53:976– 978. 3. Wu Z, Zhou Q, Wang DJ: An intracardiac ectopic thyroid adenoma. Interact Cardiovasc Thorac Surg 2009;8:587– 588. 4. Hirnle T, Szymczak J, Ziolkowski P, et al: Ectopic thyroid malignancy in the right ventricle of the heart. Eur J Cardiothorac Surg 1997;2:147–149. 5. Noussios G, Anagnostis P, Goulis DG, et al: Ectopic thyroid tissue: anatomical, clinical, and surgical implications of a rare entity. Eur J Endocrinol 2011;165:375–382. 6. Ibrahim NA, Fadeyibi IO: Ectopic thyroid: etiology, pathology and management. Hormones (Athens) 2011; 10:261–269. 7. Rogers WM, Kesten HD: A thyroid mass in the ventricular septum obstructing the right ventricular outflow tract and producing a murmur. J Cardiovasc Surg 1963;4:175– 180. 8. Pollice L, Caruso G: Struma cordis: Ectopic thyroid goiter in the right ventricle. Arch Pathol Lab Med 1986;110:452– 453. 9. Rose AG, Novitzky D, Price SK: Heterotopic thyroid tissue in the heart. Am J Cardiovasc Pathol 1988;1:401–404. 10. Porqueddu M, Antona C, Polvani G, et al: Ectopic thyroid tissue in the ventricular outflow tract: Embryologic implications. Cardiology 1995;86:524–526. 11. Casanova JB, Daly RC, Edwards BS, et al: Intracardiac ectopic thyroid. Ann Thorac Surg 2000;70:1694–1696. 12. Ruberg FL, McDonnell ME, Trabb J, et al: An intracardiac accessory thyroid gland. Am J Cardiol 2006;97:926– 928. 13. Chitwood WR Jr: Cardiac neoplasms: Current diagnosis, pathology, and therapy. J Card Surg 1988;3:119–154. 14. Rieser GD, Ober KP, Cowan RJ, et al: Radioiodide imaging of struma cordis. Clin Nucl Med 1988;13:421–422. 15. Ansani L, Percoco G, Zanardi F, et al: Intracardiac thyroid heterotopia. Am Heart J 1993;125:1797–1801. 16. Kasprzak JD, Religa W, Krzeminska-Pakula M, et al: Right ventricular outflow tract obstruction by cardiac metastasis as the first manifestation of follicular thyroid carcinoma. J Am Soc Echocardiogr 1996;9:733–735. 17. Irvine RW, Ramphal PS, Hall C, et al: Struma cordis in a Jamaican woman. Interact Cardiovasc Thorac Surg 2005; 4:83–84.
155
REVIEW ARTICLE _______________________________________________________________
Intracardiac Ectopic Thyroid (Struma Cordis) Josef Besik, M.D., Ph.D.,* Ondrej Szarszoi, M.D., Ph.D.,* Anastazie Bartonova, M.D.,y Ivan Netuka, M.D., Ph.D.,*,z Jiri Maly, M.D., Ph.D.,* Marian Urban, M.D.,* Jozef Jakabcin, M.D., Ph.D.,§ and Jan Pirk, M.D., Ph.D.* *Department of Cardiac Surgery, Institute for Clinical and Experimental Medicine, Prague, Czech Republic; yDepartment of Pathology, Institute for Clinical and Experimental Medicine, Prague, Czech Republic; z2nd Department of Surgery, Department of Cardiovascular Surgery, First Faculty of Medicine, Charles University in Prague, Prague, Czech Republic; and §Department of Cardiology, Masaryk Hospital, Usti nad Labem, Czech Republic ABSTRACT A 67-year-old male with a history of gastrointestinal malignancy was found to have a tumor in the right ventricular outflow tract. The tumor was surgically removed, and the histological diagnosis was thyroid struma. We review the literature on this rare cardiac tumor. doi: 10.1111/jocs.12245 (J Card Surg
2014;29:155–158)
Intracardiac ectopic thyroid (struma cordis) is a rare cardiac neoplasm. The first case of ectopic thyroid tissue in the right ventricular cavity was made during a routine autopsy by Dosch in 1941.1 The first successful surgical removal of an intracardiac goiter was documented by Lo et al. in 1984.2 Worldwide, 33 case reports have been published to date (Table 1), including a case of adenoma and invasive follicular carcinoma.3,4 PATIENT PROFILE A 67-year-old male was admitted with dyspnea on exertion (New York Heart Association functional class II [NYHA II]) 10 months following a sigmoid colon resection for adenocarcinoma found in a polyp (cancer stage T1N0M0). Transesophageal echocardiography showed an oval mass 30 mm 27 mm 24 mm in size, ‘‘gelatinous’’ in character with small cavities, broadly attached to the interventricular septum in the region of the right ventricular outflow tract (RVOT) (Fig. 1). The function of both ventricles as well as all heart valves was normal. Due to suspected adenocarcinoma metastasis, magnetic resonance imaging (MRI) (Fig. 2) and positron emission tomography/computed tomography (PET/CT) examinations were also performed. In both procedures, the tumor showed low contrast medium (glucose) saturation, which Conflict of interest: The authors acknowledge no conflict of interest in the submission. Address for correspondence: Josef Besik, M.D., Ph.D., Department of Cardiac Surgery, Institute for Clinical and Experimental Medicine, Prague, Czech Republic. Fax: 00420236052776; e-mail: [email protected]
provided evidence that it was benign in nature. Tumor marker levels (alpha-1-fetoprotein, CA 72-4, CA 19-9, CEA, PSA) were within normal ranges, as were other laboratory values, including thyroid hormone levels. Abdominal sonography revealed no pathological findings. A coronary angiography showed no coronary lesion. After performing a median sternotomy, extracorporal circulation was established with bicaval cannulation and the heart was arrested with cold blood cardioplegia. After accessing the right ventricle through the right atrium and tricuspid valve, a broadly attached spherical mass 30 mm in diameter with a whitish surface was found in the right ventricular outflow tract (Fig. 3). The mass had an elastic consistency, was well-differentiated from the surrounding tissue, and showed no evidence of invasion. The tumor was excised and sent to histology for examination. The histology was composed of thyroid tissue showing features of a colloid goiter. An immunohistochemical examination using anti-thyroglobulin antibodies and TTF 1 was positive. Proliferation marker Ki-67 showed positivity in about 1% of cells. Significant cellular and nuclear atypia and mitosis were not present. The margins were free of tumor (Fig. 4). The patient tolerated the procedure well, and a predischarge transthoracic echocardiography showed no pathological findings and the function of both ventricles and the valves were normal. Three months after surgery the patient feels very well and his dyspnea resolved. He has normal thyroid function. Ultrasonography showed the thyroid in the normal position and somewhat enlarged with micronodular remodeling, not requiring any intervention at present.
156
BESIK, ET AL. INTRACARDIAC ECTOPIC THYROID
J CARD SURG 2014;29:155–158
TABLE 1 Literature Review of Struma Cordis Pat.
Year
Authors
Journal
Gender
Age
Loc.
1 2 3 4 5 6
1941 1963 1982 1984 1985 1986 1986 1986 1987 1988 1988 1988 1988 1989 1990 1993 1993 1993 1995 1994 1995 1995 1995 1996 1997 1997 1999 2000 2000 2002 2003 2005 2006 2009 2009 2011 2011
Dosch1 Rogers and Kesten7 Zorina Lo et al.2 Shemin et al. Kantelip et al. Peycelon et al. Pollice and Caruso8 Grigg et al. Greco-Lucchina et al. Kon et al. Rieser et al.14 Rose et al.9 Doria et al. Richmond et al. Ansani et al.15 Kerlan et al. Polvani et al. Porqueddu et al.10 Maillette et al. Dresler et al. Dresler et al. Castaldo et al. Fujioka et al. Hirnle et al.4 Archundia et al. Pistono et al. Casanova et al.11 Baykut et al. Chosia et al. Larysz et al. Irvine et al.17 Ruberg et al.12 Comajuan et al. Wu et al.3 Fennira et al. Scrofani et al.
Beitr Pathol Anat J Cardiovasc Surg Arkh Patol Am J Cardiol Am J Cardiol Hum Pathol Ann Chir Arch Pathol Lab Med J Am Coll Cardiol Am Heart J Ann Thorac Surg Clin Nucl Med Am J Cardiovasc Pathol Chest Thorax Am Heart J Ann Endocrinol (Paris) Ann Thorac Surg Cardiology Can J Cardiol Dtsch Med Wochenschr Dtsch Med Wochenschr Arch Mal Coeur Vaiss Chest Eur J Cardiothorac Surg Arch Inst Cardiol Mex Cardiologia Ann Thorac Surg Ann Thorac Surg Pol J Pathol Kardiol Pol Interact Cardiovasc Thorac Surg Am J Cardiol Eur J Echocardiogr Interact Cardiovasc Thorac Surg Ann Cardiol Angeiol (Paris) J Cardiovasc Med (Hagerstown)
F F F F F M M F F M F F F F F F F F F F F F F M F F F F F F F F F F F F F
67 51 60 47 58 25 25 59 57 59 56 56 51 66 63 75 51 66 66 63 34 61 43 50 55 33 64 66 42 48 48 46 62 74 33 50 45
RVOT RVOT RVOT RVOT RVOT RVOT RVOT RVOT RVOT RVOT LVOT LVOT RA RVOT RVOT RVOT RVOT RVOT RVOT RVOT RVOT RVOT RVOT RVOT RVOT IVS RVOT RVOT LVOT RVOT RVOT RVOT RVOT RVOT RVOT RVOT RVOT
7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33
F, female; IVS, interventricular septum; LVOT, left ventricular outflow tract; M, male; RA, right atrium; RVOT, right ventricular outflow tract.
DISCUSSION Ectopic thyroid is defined as the finding of isolated thyroid tissue outside of its usual pretracheal location. Ectopia is caused by a disturbance in early embryonic
Figure 1. Two-dimensional transesophageal echocardiography shows an oval mass attached to the interventricular septum in the right ventricular outflow tract (RA, right atrium; RV, right ventricle; AV, aortic valve; T, tumor).
Figure 2. Cardiac magnetic resonance imaging (2D cine tfi sequence) shows a tumor in the RVOT (Ao, aorta; PA, pulmonary artery; T, tumor).
J CARD SURG 2014;29:155–158
Figure 3. Intraoperative photograph shows the tumor (T) in the right ventricle after right atriotomy and retraction of the anterior tricuspid leaflet (not shown).
development. The embryonic thyroid gland begins to develop on approximately the 24th day of gestation as a proliferation of endodermal cells on the base of the primitive pharyngula, at the site of the later foramen caecum linguae, the median anlage. Two lateral anlages and an ultimobranchial body, containing parafolicular cells originating from the neural crest, are formed from the fourth pharyngeal pouch. In this period the thyroid primordium is in close proximity to surrounding structures, including the primitive heart. In subsequent development, the median anlage fuses with the lateral anlage, creating and lengthening what is initially the hollow thyroid diverticulum (later the thyroglossal duct), through which the organ descends to its final location in the neck. The thyroid gland takes its final shape and place in the seventh week of embryonic development. A failure in this descent leads to the ectopic development of all or part of the thyroid gland, which is drawn to another organ or tissue. A failure in the fusion of the medial and lateral anlages then creates a rare lateral goiter, in most cases in the submandibular region.5,6 The overall prevalence of ectopic thyroid is 1 per 300,000 to 400,000; among patients treated and
Figure 4. A histological picture of the excised tumor reveals colloid-filled thyroid tissue with no signs of malignancy (haematoxylin and eosin stain, magnification 100).
BESIK, ET AL. INTRACARDIAC ECTOPIC THYROID
157
monitored for thyroid disease the prevalence is 1 per 4000 to 8000. However, in autopsy studies, prevalence is far greater and reaches up to 10%. Females are affected significantly more often than males. The most frequent form is lingual thyroid (90% of cases). Sublingual placement is less common and includes: suprahyoid and infrahyoid, in the thyroglossal duct, trachea, lungs, mediastinum, aortic arch, or pericardium, including the heart. In extremely rare cases, thyroid tissue is found in the subdiaphragmatic region, such as the gastrointestinal tract, porta hepatis, pancreas, adrenal gland, gall bladder, or urinary bladder.5 The cause seems to be due to aberrant embryonic thyroid tissue migration or heterotopic differentiation of uncommitted endodermal cells. Struma ovarii develops as a part of a monodermal teratoma of the ovary.5 The same pathological processes may develop in ectopic thyroid as in the orthotopic thyroid, including benign and malignant tumors.3,4 Ectopic thyroid in the heart (struma cordis) is a rare finding. Like ectopic tissue in other locations, intracardiac ectopic thyroid arises during embryonic development. It is highly likely that ectopic thyroid is a result of aberrant migration of embryonic thyroid tissue, occurring while the thyroid primordium is in close contact with the embryonic heart, when the posterior part of the primordium is incorporated into the primitive heart.7 The thyroid primordium always comes into contact with the primitive heart at the same site, the bulbus cordis. The outflow tracts of both ventricles are formed from the distal part of the bulbus (infundibulum). The anterolateral part of the infundibulum develops into the right ventricular outflow tract, and the posteromedial part becomes the outflow tract of the left ventricle.8 Only 33 cases of struma cordis have been published worldwide (Table 1). Except for a single finding in the right atrium,9 in every case the ectopic thyroid tissue grew from the interventricular septum and usually spread to the right ventricular outflow tract (29 cases of 33) or, less often, to the left ventricular outflow tract (three cases). Porqueddu et al. suggest that the cause of ectopic thyroid predominantly occurring in the right ventricular outflow tract is most likely due to the persistent contact between the thyroid primordium and anterolateral part of the primitive heart infundibulum, which is the anlage for the development of the right ventricular outflow tract.10 Several authors also mention the possible role of the abnormal migration of neural crest cells.11 The majority of patients are females (30 cases of 33), usually in middle or advanced age. The most common clinical symptoms are varying degrees of shortness of breath after exertion, or sometimes ventricular arrhythmia or pulmonary embolism.12 Some patients are entirely asymptomatic. An echocardiography performed due to cardiac symptomatology or as a routine heart test for an unrelated condition finds a cardiac tumor that is several centimeters in size. The mass almost always originates in the interventricular septum, is usually broadly attached, and protrudes into the right ventricular outflow tract, where it may cause varying degrees of obstruction.
158
BESIK, ET AL. INTRACARDIAC ECTOPIC THYROID
Various types of abnormal masses may occur in the right ventricle—blood clots, benign tumors (usually myxoma, lipoma, papillary fibroelastoma, or rhabdomyoma), malignant primary tumors (sarcoma), and malignant secondary tumors (metastasis).13 When a tumor is found in the right ventricular outflow tract, especially in middle-aged women, intracardiac ectopic thyroid should be considered. If this possibility is suspected, thyroid scintigraphy may be performed to confirm the diagnosis before cardiac surgery.14 We believe it can modify the surgical strategy. Removal of an unknown tumor would be potentially dangerous— there is a risk of iatrogenous interventricular septum injury in case of extensive resection, which is not necessarily needed in cases of struma cordis. Ansani et al. also mention that the right ventricular outflow tract is a frequent site of metastasis. Thyroid carcinoma in particular frequently metastasizes to the heart and it has been suggested that a preoperative thyroid scan might be useful in patients with echocardiogram showing a right ventricular mass partially obstructing the outflow tract.15 If one entertains the possibility of a thyroid nodule within the heart, a neck ultrasound could be useful to identify primary thyroid pathology, such as a follicular tumor that has conceivably metastasized to the heart. Complete removal of struma cordis is usually a safe procedure. Histological diagnosis normally does not represent a problem. It is always very important to rule out the possibility of cardiac metastasis of highly differentiated follicular thyroid cancer.16 It is recommended to perform thyroid function test several weeks after the operation to rule out potential hypothyroidism. No case of thyroidectomy in patients after struma cordis removal was reported. The long-term prognosis for patients is good.17 REFERENCES 1. Dosch F: U¨ber einen Fall von Glandula thyroidea accessoria intracardialis. Beitr Pathol Anat 1941;105: 244–255.
J CARD SURG 2014;29:155–158
2. Lo HM, Tseng YZ, Tseng CD, et al: Intracardiac goiter: A cause of right ventricular outflow tract obstruction and successful operative therapy. Am J Cardiol 1984;53:976– 978. 3. Wu Z, Zhou Q, Wang DJ: An intracardiac ectopic thyroid adenoma. Interact Cardiovasc Thorac Surg 2009;8:587– 588. 4. Hirnle T, Szymczak J, Ziolkowski P, et al: Ectopic thyroid malignancy in the right ventricle of the heart. Eur J Cardiothorac Surg 1997;2:147–149. 5. Noussios G, Anagnostis P, Goulis DG, et al: Ectopic thyroid tissue: anatomical, clinical, and surgical implications of a rare entity. Eur J Endocrinol 2011;165:375–382. 6. Ibrahim NA, Fadeyibi IO: Ectopic thyroid: etiology, pathology and management. Hormones (Athens) 2011; 10:261–269. 7. Rogers WM, Kesten HD: A thyroid mass in the ventricular septum obstructing the right ventricular outflow tract and producing a murmur. J Cardiovasc Surg 1963;4:175– 180. 8. Pollice L, Caruso G: Struma cordis: Ectopic thyroid goiter in the right ventricle. Arch Pathol Lab Med 1986;110:452– 453. 9. Rose AG, Novitzky D, Price SK: Heterotopic thyroid tissue in the heart. Am J Cardiovasc Pathol 1988;1:401–404. 10. Porqueddu M, Antona C, Polvani G, et al: Ectopic thyroid tissue in the ventricular outflow tract: Embryologic implications. Cardiology 1995;86:524–526. 11. Casanova JB, Daly RC, Edwards BS, et al: Intracardiac ectopic thyroid. Ann Thorac Surg 2000;70:1694–1696. 12. Ruberg FL, McDonnell ME, Trabb J, et al: An intracardiac accessory thyroid gland. Am J Cardiol 2006;97:926– 928. 13. Chitwood WR Jr: Cardiac neoplasms: Current diagnosis, pathology, and therapy. J Card Surg 1988;3:119–154. 14. Rieser GD, Ober KP, Cowan RJ, et al: Radioiodide imaging of struma cordis. Clin Nucl Med 1988;13:421–422. 15. Ansani L, Percoco G, Zanardi F, et al: Intracardiac thyroid heterotopia. Am Heart J 1993;125:1797–1801. 16. Kasprzak JD, Religa W, Krzeminska-Pakula M, et al: Right ventricular outflow tract obstruction by cardiac metastasis as the first manifestation of follicular thyroid carcinoma. J Am Soc Echocardiogr 1996;9:733–735. 17. Irvine RW, Ramphal PS, Hall C, et al: Struma cordis in a Jamaican woman. Interact Cardiovasc Thorac Surg 2005; 4:83–84.
