A 60-year-old gentleman with past medical history of cervical disk herniation presented with a 3-year history of progressive fatigue and bilateral upper extremity weakness. MRI was performed to evaluate the spine and was consistent with cervical spinal stenosis. T2 non-contrast images incidentally revealed an infiltrating mass in the left thyroid that was incompletely visualized. Ultrasound-guided fine needle aspiration showed atypia of undetermined significance. The patient was referred to surgery and was noted to have dysphonia but no stridor or dysphagia. The differential diagnosis was felt to include papillary thyroid carcinoma, follicular thyroid carcinoma, rare thyroid neoplasms including Hurthle cell carcinoma or anaplastic carcinoma, abscess, or autoimmune thyroid disease. He underwent total thyroidectomy with central neck dissection. On exploration, the thyroid mass was seen encasing the left recurrent laryngeal nerve and was shaved off the nerve and the trachea. The nerve was not stimulatable after resection and the patient developed left vocal cord paralysis. The tumor grossly measured 7 cm with extrathyroidal extension. There was lymphvascular space invasion and perineural invasion. Three lymph nodes were identified, and all were negative. Surgical margins had extensive involvement of tumor. Histopathologic analysis of the specimen showed high-grade carcinoma with thymus-like differentiation. Immunohistochemical staining was positive for pan-CK, p63 (cyokeratin and epithelial markers) and negative for chromogranin, thyroglobulin, and calcitonin (neuroendocrine, papillary and follicular thyroid, and medullary makers, respectively).\nThe tumor was arranged in broad, pushing, smooth-bordered islands abutted against a lymphocyte rich stroma. The lobules of tumor were surrounded by lymphocytes and plasma cells (Figures and ). The tumor cells were squamoid and syncytial to spindled, with eosinophilic cytoplasm, and the nuclei show mild pleomorphism with pale vesicular chromatin. The neoplastic cells were strongly immunoreactive for pancytokeratin and p63, as shown in Figures and . These cells were also strongly positive for CD5, which marks background T lymphocytes (Figure ). The neoplastic cells were non-reactive with TTF1 and thyroglobulin.\nPostoperative staging surveillance with PET scan was performed for systemic staging and due to positive margins. It showed no abnormal FDG uptake at distant sites and increased uptake at the operative bed, indeterminate between residual disease and postoperative changes. The patient underwent adjuvant treatment with radiation therapy to 64 Gy in 32 fractions with intensity modulated radiotherapy. Concurrent chemotherapy was given based on his extensive positive margins for radiosensitization. A dose of 60 Gy was delivered to the bilateral neck including paratracheal nodes into the upper mediastinum, with a 4 Gy sequential boost to the operative site. A coronal section of the radiotherapy plan is shown in Figure . Six cycles of intravenous concurrent cisplatin 35 mg/m2 were infused. During therapy, he developed grade 2 skin reaction characterized by dry desquamation and moderate erythema of the neck and upper chest. Skin moisturizer was used for therapy. He experienced grade 2 esophagitis and mucositis of the oropharynx and grade 2 nausea requiring topical analgesics, oral narcotics, antiemetics, and intravenous fluid administration. Weight decreased from 108 to 95.5 kg by the end of therapy. Nutritional counseling by dietician and oral nutritional supplementation were provided. With chemotherapy, the patient developed a tinnitus grade 1. Toxicities are reported per the Common Terminology Criteria for Adverse Events ().\nAfter treatment, the patient initially experienced continued weight loss, and as a result underwent percutaneous endoscopic gastrostomy tube placement. Five months after end of treatment, the tube was removed after the patient was able to gain significant weight and completely obtain nutrition per oral route for 6 weeks. Dysphagia to solid foods is improving. He experienced persistent dysphonia secondary to left vocal cord paralysis since surgery and underwent left medialization thyroplasty 1 year later. He displayed improvement in voice quality. At 3-years follow-up after completion of radiotherapy, our patient is without evidence of locally recurrent or distant disease.
A 60-year-old woman, who was diagnosed with cancer of the thyroid gland in 2015, was treated with total thyroidectomy and lymph node dissection. Her postoperative pathology showed carcinoma showing thymus-like differentiation (CASTLE). She was discharged on Levothyroxine 100 mg/day. She did not attend her follow-up appointments. After 2 years, the patient found a lump in the left side of her neck. The tumor grew very slowly and did not cause any symptoms; hence, she did not seek medical advice. In May 2020, about 3 years after the appearance of her left neck tumor, the patient was admitted to our hospital with shortness of breath due to tracheal compression from the tumor. Clinical examination showed enlarged solid painless cervical lymph nodes at levels III and IV, stuck in a block size of 3 × 6 cm in diameter. There was no involvement of the hypopharynx, and her vocal cords were intact. CT scan of her neck revealed a 16 × 54 mm lesion compressing the trachea, and several enlarged left cervical lymph nodes with the size of about 25 mm (Fig. ). The patient was offered a tracheostomy and tracheal stent before undertaking further investigations.\nHer subsequent fluorine-18-labeled fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) scan revealed previous total thyroidectomy, no evidence of recurrence in the surgical bed, enlarged left cervical lymph nodes at levels III and IV, and extranodal extension into sternocleidomastoid muscle measuring 29 × 43x59 mm, with the maximum standardized uptake value (SUV max) of 6.8. Her thymus measured 19 × 31x37mm, with increased metabolism of FDG (SUV max 3.6). There was a 33 × 39x49 mm mass on the left side of the anterior mediastinum, showing an undefined margin with neighboring organs in the trachea and the thorax (SUV max 6.0). It also showed multiple lymph nodes near the lower trachea, next to the superior vena cava, posterior thymus, and aortic loop; the largest node was 26 × 40 mm, with increased metabolism of FDG (SUV max 7.9). The other organs were unaffected. There was no metastasis in other organs (Fig. ).\nThyroid function tests showed TSH: 0.00726 mIU/L[0,4-5], FT4: 22.34 pmol/L [12-22] and FT3: 4.0 pmol/L [1, 3-3, 1]. We reviewed the pathology of the current cervical lymph node specimen and that of the thyroid specimen from 5 years ago (2015). This showed that the thyroid tumor consisted of invasive cells which were poorly differentiated with squamous cell morphology, different from conventional thyroid carcinoma. The immunohistochemistry (IHC) analysis showed positive staining with CK5, CK7, p63, C-kit, CD5 and negative with TTF-1, Thyroglobulin, GATA3, ER, CD99, and NKX2.2, confirming CASTLE pathology in both the specimens.\nThe patient was diagnosed with a recurrence of the CASTLE thyroid gland in cervical lymph nodes. She was assessed by thoracic, and head and neck surgeons for the possibility of removing the maximum of recurrent tumors. However, it was considered a difficult, high-risk procedure; she and her family declined to go ahead with the surgery. Then, we offered the patient treatment with palliative radiotherapy. However, she and her family declined the treatment and got the patient discharged from the hospital. She was followed up without intervention and is currently stable 15 months after the recurrence.