Evolution and evaluation of lateral cystic neck masses containing thyroid tissue: “Lateral aberrant thyroid” revisited

Evolution and Evaluation of Lateral Cystic Neck Masses Containing Thyroid Tissue: “Lateral Aberrant Thyroid” Revisited C. Rose Rabinov, MD, Paul H. Ward, MD, and Teresa Pusheck, MD

The usual differential diagnosis of a lateral cystic neck mass places emphasis on benign entities. This is particularly true in the evaluation of patients under the age of 40. Generally included in the differential are branchial cleft cyst, lymphangioma, hemangioma, laryngocele, pharyngeal diverticulum, and infectious adenopathy or abcess. While metastatic cervical adenopathy is also included in the differential, it is generally placed quite low on the list. Metastasis from thyroid carcinoma is often not mentioned at all. Delayed or missed diagnosis can occur if malignancy is not considered in the differential. This report reviews the historical evolution of scientific thinking regarding thyroid gland embryology and the origin of lateral neck masses of thyroid histology. An illustrative case is described in which metastatic papillary thyroid carcinoma presented in the typical manner of a branchial cleft cyst. The preoperative evaluation and management of such patients is discussed. BACKGROUND Historically, thyroid carcinoma found in the lateral neck was considered to be a primary tumor rather than a metastatic deposit. In 1906, Schrager’ defined aberrant thyroid as “a mass of tissue having the structure of normal or pathologic thyroid, and situated at some definite distance from the normal thyroid, with which it has no connection whatever.” He described in detail the then ongoing debate over the origin of these masses. It was generFrom the Division of Head and Neck Surgery University of California, Los Angeles, CA. Address reprint requests to C. Rose Rabinov, MD, Division of Head and Neck Surgery, University of California, Los Angeles, 10833 Le Conte Ave, Los Angeles, CA 90024. Copyright Q 1996 by W.B. Saunders Company 0196-0709/96/l 701-0002$5,00/O 12

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ally held that the lateral lobes of the thyroid gland arose separately from, and developed independently of the “median lobe.” The lateral lobes, having come from either an area at the lateral pharyngeal floor or from the epithelium of the fourth branchial cleft, were thought to descend separately from the central aspect of the thyroid gland. During the descent of the lateral lobes, the concurrent normal growth of neck vessels and musculature resulted in pressure on and detachment of segments of thyroid tissue. This was believed to be the origin of the masses of thyroid tissue found laterally in the neck with no apparent connection to the thyroid gland proper. At approximately the seventh intrauterine week, there was medial migration and fusion of the three lobes.‘J Despite misconceptions regarding their embryology, the description of these lateral neck masses was characteristic of that of metastatic papillary thyroid carcinoma. The location of “aberrant” thyroids was described most often as being coincident with the jugular nodal chain or in the anterior cervical triangle. Many were cystic in nature, being filled with “chocolate-colored” fluid,’ and containing microscopically identified thyroid tissue in the surrounding wall. 3 The patients were usually young females, a finding that was attributed to tumor enlargement being secondary to a disturbance in menstruation or “to the endocrine demands of pregnancy.“4 The existence of primary thyroid disease metastatic to the neck continued to be a matter of dispute into the early 1940s. Several reports were published describing patients who had presented with palpable cervical masses and simultaneous thyroid nodules. Despite the fact that the two specimens had identical histology, it was generally believed that “the process originated laterally and medially at the same time.“4 In addition, because of prob-

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able confusion over histologic criteria of malignancy and because of the extremely slow growth of many of these tumors, they were often diagnosed as benign entities, such as papillary adenoma or papillary cystadenoma of the “lateral aberrant thyroid.“2,5 The minority view held that these lateral masses might actually be metastasis from the thyroid gland itself.” Through their review of 54 cases, King and Pemberton” presented the first substantial evidence for the true nature of metastatic cervical deposits of thyroid origin. They deemed 51 of their patients with laterally placed thyroid tissue to have malignant disease, based on the histologic findings of vascular, capsular, and lymphatic invasion. Furthermore, 55% of these “tumors contained lymphoid tissue, usually in the form of a shell around the cancerous tissue with finger-like processes extending into it.” They found support for the “metastatic” theory in the fact that midline thyroid tumors, when present (60%), were histologically identical to the lateral neck tumors. When concurrent, thyroid and cervical masses were always found on the same side of the neck. In addition, most of the cervical tumors were found in locations coincident with those of deep cervical lymph nodes. Between the mid-1940s and the early 1980s intermittent case reports of patients with papillary thyroid carcinoma presenting solely with lateral cervical metastases appeared in the literature. Searls et al7 published a retrospective study spanning 38 years in which they reported 22/260 cases of patients with carcinoma of the thyroid in whom the initial manifestation was that of a lateral neck mass. Crile, having previously reported 13 cases of “lateral aberrant thyroid,“s re-presented this series with 9 additional cases.g With this second publication, however, he wrote in support of the idea that these patients most likely had laterally placed cervical metastases rather then primary tumors of the neck. Neither of these authors described a cystic versus solid nature of their patients’ neck disease, although two of Searls’ cases were given the preoperative diagnoses of branchial cleft cyst. Current teaching describes the thyroid gland as originating from a single site at the pharyngeal floor. From its beginnings at the foramen cecum, the bilobed gland descends in the

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midline of the neck to reach its adult positioning in front of the trachea (Fig 1). The term “aberrant thyroid” now refers to the tissue that fails to complete this normal descent, most commonly lingual thyroid (Fig 2).l” Tissue with thyroid histology found lateral to the midline is considered to be malignancy metastatic from the thyroid gland itself. CASE REPORT A. G. is a 34-year-old white male who initially presented with a B-month history of an enlarging right neck mass. He had recently undergone extraction of several right mandibular teeth and was being treated with antibiotics for presumed dental infection without any decrease in the size of the mass. The patient had actually first noted a lump in his right neck several years before this presentation, but sought treatment at this time because of progressive increase in size of the mass. He denied any history of trauma, dysphagia, voice change, or weight loss. He admitted to smoking one pack of cigarettes per day for the preceeding twenty years, as well as being a recovering alcoholic and intravenous drug abuser. His past medical history was also significant for Hepatitis C infection. He denied having had any recent symptoms of upper respiratory tract infection. On examination a 6 X 5-cm, non-tender, fluctuant mass was palpated in the upper right neck just anterior to and partially deep to the sternocleido-

Foromen

Fig 1. Embryologic shown in the midline adult trachea.

from

cecum

descent of the thyroid gland is the tongue base to level of the

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The patient subsequently underwent a total thyroidectomy and right modified neck dissection, with resection of the internal jugular vein and its associated lymph nodes. On gross examination, the thyroid gland appeared entirely normal. A single enlarged high jugulodigastric lymph node was noted. Histopathology revealed 2/21 nodes positive for metastatic thyroid carcinoma in the neck specimen. In addition, a small focus of papillary carcinoma was found in the superior portion of the right thyroid lobe.

DISCUSSION

Fig 2. Possible sites of aberrant thyroid tissue along the line of embryologic descent. Lingual thyroid is most common, being located at the level of the foramen cecum.

mastoid muscle. Additionally, a tender 2-cm submandibular mass was noted. No other neck masses were felt; specifically, the thyroid gland was without nodules or induration. The remainder of head and neck examination, including visualization of the oral cavity, pharynx and an indirect laryngoscopy, was unremarkable. No active dental disease was present. A fine needle aspiration of the mass produced only hemorrhagic cystic fluid. Preoperative laboratory evaluation, including CBC, electrolyte panel, and chest x-ray, were all within normal limits. The patient was taken to surgery for excision of a presumed right branchial cleft cyst. Intraoperatively a 5 x J-cm cystic mass was removed along with several associated lymph nodes from the right anterior neck. No sinus tract was found. The mass itself, however, lay partially between the internal and external carotid arteries. No frozen sections were requested during the procedure. Postoperatively, histopathologic examination of the encapsulated cystic mass revealed a well- differentiated cystic papillary thyroid carcinoma with old hemorrhage. All associated lymph nodes were negative for evidence of malignancy. In light of these unexpected findings, the patient was scheduled for further metastatic evaluation. Thyroid scan showed only normal uptake. Computed tomography (CT) scan with contrast did not reveal any further metastatic deposits in the neck. Thyroid function tests were also within normal limits.

The above case, as well as those outlined in historical review, illustrate the fact that lateral cystic cervical masses should not be presumed benign. Current teaching regarding the work-up of a solitary neck mass mandates full evaluation for possible primary malignant disease before performing any open procedure for diagnostic biopsy. While this teaching is widely accepted for solitary solid cervical masses, lateral cystic neck masses are more commonly assumed to be benign and are often primarily excised with minimal preliminary evaluation. This is especially true in the evaluation of younger patients. Indeed, major otolaryngology texts note that “the immediate removal of an enlarged lymph node for diagnostic purposes is a disservice to the patient with metastatic cervical carcinoma,” but that in the “child, adolescent, and young adult” age groups, “the diagnostic step of preference is the immediate open biopsy with histologic examination, followed later by staging procedures, as necessary.“” Tovilz and Wallace,13 through their reports of 8 separate cases, delineated preoperative evaluation of patients with papillary thyroid carcinoma presenting with a solitary cervical cyst. Their assessments included thyroid function tests (TFTs), chest radiographs (CXR), thyroid scan, and ultrasonography (UTZ). Fine needle aspirate was included in some cases with a yield of “brown-murky fluid” without evidence of malignant cells present on smear.13 CXR and TFTs were found to be normal in all patients. Thyroid scans (99mTc) were normal in the majority, but revealed a cold nodule in the ipsilateral thyroid lobe of one patient and showed “patchy uptake” in another. While UTZ was used to confirm the cystic nature of the tumors in both studies, Wallace also re-

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ported that UTZ revealed “internal echoes” within these cysts. More recently, the use of UTZ in the evaluation of cystic neck masses has been supported. Loughran14 reported on a 1%year-old patient with a presumed right-sided branchial cleft cyst. UTZ examination revealed a cystic mass with an internal lining that was “thickened and irregular.” In addition, “occasional incomplete septa were noted within it.” Levy15 reported similar findings in a 4%year- old female. Both of these patients were ultimately diagnosed as having cystic cervical metastasis from occult papillary thyroid carcinoma. As branchial cleft cysts are characteristically smooth-walled, echo-free lesions on UTZ, it is recommended that a high index of suspicion for alternate diagnosis be kept when findings vary from this classic description. It has been further suggested that UTZ of the thyroid gland itself be added to this examination and that FNA be carried out on any solid lesion detected.12 CONCLUSION Cystic masses in the neck may be malignant thyroid tissue. An understanding of the embryology of the thyroid gland helps to explain these unusual tumors. We recommend that all patients undergoing evaluation of a cystic neck mass be evaluated for the possibility of malignancy. Preoperative evaluation should include fine needle aspiration of any fluid within the cyst, with repeat aspiration of any palpable mass remaining. Atypical findings on ultrasound or CT scan may increase suspicion of malignancy and be used to help guide needle biopsy. If definitive diagnosis is unknown preoperatively, surgeons should have

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patients sign appropriate consent forms such that, if intraoperative frozen section of any solid component found reveals malignancy, definitive surgical therapy may be carried out without delay. REFERENCES 1. Schrager VL: Lateral aberrant thyroids. Surg Gynecol Obstet 3:465-475,1906 2. Frantz VK, Forsythe R, Hanford JM, et al: Lateral aberrant thyroids. Ann Surg 115:161-183,1943 3. King WM, Pemberton J deJ: So called lateral aberrant thyroid tumors. Surg Gynecol Obstet 74:991-1001,1942 4. Ward R: Relation of tumors of lateral aberrant thyroid tissue to malignant disease of the thyroid gland. Arch Surg 40:606-645,194O 5. Smith MK: Papillary adenoma of aberrant thyroid. Ann Surg 113:77-81,1941 6. Pemberton J deJ: Ann Surg 100:906-923, 1934, in King WM, Pemberton J deJ: So called lateral aberrant thyroid tumors. Surg, Gyenecol Obstet 74:991-1001, 1942 7. Searls HH, Davies 0: Metastatic carcinoma of the thyroid gland as the initial manifestation of the disease. California Medicine 76:62-65,1952 8. Crile G: Tumors of lateral aberrant thyroid origin. J Am Med Assoc, 113:1094-1097,1939 9. Crile G: Papillary carcinoma of the thyroid and lateral cervical region: So called “lateral aberrant thvraid.” Surg, Gynecol Obstet, 85:757-766,1947 10. Sadler TW: Head and neck. in Lanaman’s Medical Embryology (ed 5). Baltimore, MD, Williims & Wilkins, 1985, pp 293-295 11. McGuirt WF: Neck mass: Patient examination and differential diagnosis, in Cummings CW, Schuller DE (eds): Otolaryngology-Head and Neck Surgery CV Mosby, St Louis, MO, 1986, pp 1587-1595 12. Tovi F, Zirkin H: Solitary lateral cervical cyst: Presenting symptom of papillary thyroid adenocarcinoma. Ann Otol Rhino1 Laryngol92:521-524, 1983 13. Wallace MP, Betsill WL: Papillary carcinoma of the thyroid gland seen as lateral neck cyst. Arch Otolaryngol 110:408-411,1984 14. Loughran CF: Case report: Cystic lymph node metastasis from occult thyroid carcinoma: A sonographic mimic of a branchial cleft cyst. Clinical Radiology 43:213214, 1991 15. Levy I, Barki Y, Tovi F: Giant cervical cyst: Presenting symptom of an occult thyroid carcinoma. J Laryngol Otol105:863-864, 1991