A 52-year-old woman was referred to our hospital because of severe dyspnea and the presence of a neck tumor. She had experienced dyspnea for the past 6 months and had recently noticed bloody sputum. A computed tomography examination of the neck revealed a thyroid tumor about 8 cm in size. The tumor had invaded the trachea, obstructing 90% of the tracheal lumen (fig. ). An emergency tracheotomy was performed to maintain an airway through the tumor tissue. On biopsy, the tumor was diagnosed as CASTLE, suggesting a favorable prognosis if a complete resection could be performed. Magnetic resonance imaging and an esophageal fibroscopy examination revealed a low possibility of esophageal invasion (fig. ). Under general anesthesia, a thyroidectomy was initially performed via a neck incision. The invaded portion of the trachea was sharply dissected. A partial sternotomy was performed at the level of the 2nd intercostal space to identify the distal portion of the intact trachea and to mobilize the inferior tracheal segment. The trachea was transversely opened to find the intact portion. The length of the resected trachea was 6 cm (fig. ). Bilateral recurrent nerves were macroscopically preserved. We performed a suprahyoid release to mobilize the superior tracheal segment, but these mobilizations were insufficient to perform an anastomosis. Thus, to allow additional mobilization, we performed a clamshell thoracotomy and incised the pericardium 360° around the hilum, dissecting the pulmonary ligament bilaterally. These procedures allowed an anastomosis. An end-to-end bronchial anastomosis was carried out using running 4-0 PDS II sutures (Ethicon, Somerville, N.J., USA) for the membranous portion and interrupted 4-0 PDS II sutures for the cartilaginous portion. The bronchial anastomosis was wrapped with an omental pedicle flap that was lifted up through a retrosternal route via a laparotomy. A gastrostomy was also performed for postoperative enteral nutrition. For management after surgery, a chin suture was placed. Neck mobilization was restricted for the placement of the chin suture and airway fixation. After confirming an improvement in the laryngeal edema using a laryngoscopy, extubation was performed on postoperative day (POD) 17. The patient exhibited swallowing disturbances and underwent swallowing rehabilitation. Enteral nutrition was provided through the gastrostomy. The patient was discharged on POD 31, and per os feeding was started on POD 51. Radiotherapy (60 Gy in 40 daily fractions of 1.5 Gy) was performed as an adjuvant therapy. Throughout the clinical course, no major complications, including swallowing disturbances, hoarseness or anastomotic problems, were observed. A histopathological examination of the resected specimen revealed the characteristic morphology of CASTLE (fig. ); immunohistochemistry was positive for CD5 (fig. ) but negative for thyroid transcription factor 1 (TTF-1; fig. ).\nEleven months after surgery, lower back pain and right leg numbness developed and led to gait inability. Multiple lung and bone recurrences were observed, but no local recurrence. In order to ease the back pain, palliative radiotherapy (35 Gy in 14 fractions) to the bone metastasis was administered. Twelve months after surgery, drainage of pleural effusion was performed. She died of pleural metastasis 14 months after the initial diagnosis of CASTLE.
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.