Occult Metastatic Papillary Thyroid Carcinoma Presenting as an Isolated Lateral Cervical Cyst

Objective | To discuss the clinical, radiologic, and cytopathologic features of papillary thyroid carcinoma (PTC) presenting as an isolated lateral cervical cyst. Methods | Retrospective case series of five adult patients presenting with isolated lateral cervical cysts that were eventually found to represent cystic metastases from PTC. Results | All but one patient were younger than 40 years of age (range 19 62). Three of the 5 were asymptomatic at presentation, and 2 presented with complaints of local discomfort or pain. Fine-needle aspiration (FNA) of the lesions was grossly abnormal in all patients, findings ranged from greenish-black, to dark-brown, to scant but hemorrhagic fluid. In three cases attention was directed towards the thyroid gland only after excisional biopsy and intraoperative histopathological examination revealed cystic lymph node metastasis from an occult PTC. In the other two cases permanent histopathological diagnosis revealed PTC and the patients were subsequently treated. Conclusion | Although the majority of isolated (occurring in the absence of a localizing primary lesion) lateral cervical cysts are benign, distinguishing these masses from metastatic carcinoma within a lymph node that has undergone cystic degeneration can be difficult. Head and neck surgeons should be mindful of the potential for malignancy in their approach to these lesions, as they often mimic benign cysts. Surgical management for definitive treatment should be dictated by the results of preoperative diagnostic imaging, FNA, and frozen-section analysis at the time of excisional biopsy. Appropriate contingency consent should be obtained in cases where preoperative workup suggests the possibility of occult malignancy. CASES CONCLUSIONS BACKGROUND Although the majority of isolated (i.e., occurring in the absence of a localizing primary lesion) lateral cervical cysts are benign, distinguishing these masses from metastatic carcinoma within a lymph node that has undergone cystic degeneration can be difficult. The diagnostic evaluation of all isolated lateral cervical cysts should include a complete clinical history, physical examination of the head and neck, imaging, FNA cytology, and excisional biopsy. In select cases, analysis of the thyroglobulin concentration in the fine-needle aspirate, and frozen-section analysis of the excised specimen are recommended. The presence of an atypical cystic pattern on imaging or a chocolate/coffee-like aspirate on FNA warrants imaging of the thyroid gland, and FNA of any suspicious thyroid lesions. Head and neck surgeons should be mindful of the potential for malignancy in their approach to these lesions, as they often mimic benign cysts. Surgical management for definitive treatment should be dictated by the results of preoperative diagnostic imaging, FNA, and frozen-section analysis at the time of excisional biopsy. Appropriate contingency consent should be obtained in cases where preoperative workup suggests the possibility of occult malignancy. Recommendations | A suspicion of malignancy should be raised in any adult who presents with a lateral cervical cyst. If history and complete head and neck physical examination, including flexible nasopharyngolaryngoscopy fails to reveal a primary site of malignancy, the lesion can be considered an isolated lateral cervical cyst. Patients are usually referred after computed tomography with contrast has already been performed. The scan should be carefully reviewed to look for an atypical/complex cystic pattern, and a primary lesion, especially in Waldeyer’s ring and thyroid gland. If no imaging has been performed, an US of the lesion is a reasonable initial diagnostic imaging modality. Evidence of an atypical/complex cystic pattern on imaging or thyroid abnormality on computed tomography warrants further investigation of the thyroid gland. Thyroid US and fine‐needle aspiration of any thyroid lesions is recommended, however, as discussed, both computed tomography and thyroid US may fail to reveal an underlying occult PTC. Fine‐needle aspiration should be performed on all isolated lateral cervical cysts. Analysis of the thyroglobulin concentration in the aspirate is recommended if the aspirate is dark or hemorrhagic. Aspiration of a chocolate/coffee‐like fluid should alert the physician to the possibility of thyroid pathology, and also warrants further investigation of the thyroid gland with thyroid US. Occasionally, cytopathological examination may reveal malignancy. More often, the results are negative or consistent with cyst contents. These negative results are considered inconclusive and do not eliminate the possibility of malignancy. Some authors suggest the use of US to examine the thyroid gland in any adult presenting with a lateral cervical cyst (14). A reasonable approach, as outlined, is to strongly consider the possibility of an occult thyroid malignancy in patients presenting with an atypical/complex cystic configuration on imaging or a chocolate/coffee‐like aspirate on FNA. Ultimately, unless the pre‐operative diagnostic work‐up reveals a primary site, excisional biopsy is required for diagnosis. Histopathological evaluation of the specimen should include meticulous examination of the cyst walls to detect minute foci of malignancy.9 It has been suggested that frozen‐section analysis of the gross specimen invariably provides the correct diagnosis, and may be a reasonable technique to guide treatment (1‐4,6,8,15,19,22,24). Intraoperatively, cystic metastic lymph nodes from PTC often demonstrate a dark pigmentation. Brown, black, blue and even purple pigmentation has been described. Clear, transluscent cysts have also been reported. A review of the literature reveals that in the reported cases of metastatic PTC presenting as a lateral cervical cyst, frozen‐section analysis correctly diagnosed carcinoma in 78% (7/9) of cases (3,4,6,8,15,19,22,24). On gross inspection, 67% of reported cases demonstrated pigmentation (Ab10,10,Ab19,9,Ab22). In the current series, frozen‐section analysis of the cyst was performed in three cases. A definitive diagnosis of metastatic PTC was made in two cases, and a suggestion of a papillary lesion in one. In all five cases, the cysts demonstrated pigmentation on gross inspection. Frozen‐section should be performed if the patient is older than 40 years of age, diagnostic imaging reveals an atypical/complex cystic pattern, FNA demonstrates a chocolate/coffee‐like aspirate or if gross examination during excision reveals a pigmented lesion. A diagnosis of squamous cell carcinoma on frozen‐section analysis warrants panendoscopy with directed biopsies of Waldeyer’s ring, and selective neck dissection. A diagnosis of PTC requires exploration of the thyroid gland, total or partial thyroidectomy, and selective neck dissection. If frozen‐section analysis demonstrates no evidence of malignancy, surgical excision of the cyst and closure of the wound is recommended. A second operation for definitive treatment is recommended if permanent histolpathological examination subsequently reveals malignancy. To avoid a second operation, many authors propose that consent be obtained for a contingency plan pending the results of the frozen‐section analysis (2‐4,6,16). This allows for definitive treatment at the time of excisional biopsy, and eliminates the risks of anesthesia associated with a second surgery. However, unless findings from the preoperative diagnostic evaluation alert the head and neck surgeon to the diagnosis prior to frozen‐section analysis, it may be difficult to determine which contingency consent to obtain. As discussed, patient characteristics and history are not always reliable predictors of the presence or type of malignancy. Nevertheless, we recommend that all adult patients who present with an isolated lateral cervical cyst be consented for excisional biopsy, possible triple endoscopy with directed biopsies, and possible neck dissection. This is especially relevant in patients older than 40 years of age, and if imaging reveals the cyst to demonstrate an atypical/complex pattern. Furthermore, if the preoperative work‐up reveals a thyroid mass or FNA demonstrates a murky, chocolate/coffee‐like aspirate, the patient should also be consented for total thyroidectomy. The excisional biopsy incision should be planned to permit neck dissection and/or total thyroidectomy should frozen‐section reveal malignancy. Finally, in the event that the pre‐operative diagnostic evaluation fails to elicit a suspicion of malignancy (i.e. complete cyst degeneration without an atypical/complex pattern on imaging and clear fluid on FNA), but frozen‐section analysis reveals metastatic PTC, a second operation is can be performed for definitive treatment after consent for total thyroidectomy is procured. Case Age/Sex Lesion duration Size Location Symptoms Radiographic findings FNA Pre-op. diagnosis 1 37 M 10 years 4.7 cm II, III None Contrast CT—round, complex cystic mass with septations and solid components lining cyst walls Dark brown fluid; no malignant cells BCC 2 30 F 6 mos. 6.0 cm II, III, IV Local pain Contrast CT—complex cystic lesion with septations, solid components within and attached to cyst wall, and areas of intermittent wall thickening with minimal peripheral enhancement Greenish-black fluid; no malignant cells BCC, lymphangioma 3 29 F 2 mos. 3.0 cm II, III Local discomfort Contrast CT—complex, well-circumscribed, heterogenous cyst with enhancing solid components and internal calcification. MR with gad—hyperintense T1 (slight) and T2 (marked); heterogenous enhancement with focus of intense enhancement. SPECT and octreotide scan within normal limits Scant hemorrhagic fluid; evidence of thyroiditis Unknown 4 19F 2 years 4.0 cm II, IV Asymptomatic, vague fullness of right thyroid lobe Noncontrast CT—confluence of three heterogeneous, complex cystic lesions with solid components Greenish‐black fluid; atypical cells of epith