Case ReportCarcinoma showing thymus-like differentiation (CASTLE) withneuroendocrine differentiation
Manabu Yamazaki,1 Satoshi Fujii,1 Hiroyuki Daiko,2 Ryuichi Hayashi2 and Atsushi Ochiai11Pathology Division, Research Center for Innovative Oncology and 2Department of Head and Neck Surgery, NationalCancer Center Hospital East, Chiba, Japan
Carcinoma showing thymus-like differentiation (CASTLE) isa rare malignant neoplasm that histologically resemblesthymic carcinoma and arises in the thyroid gland oradjacent soft tissue of the neck. Herein is reported thecase of a 62-year-old male patient with CASTLE exhibitingneuroendocrine differentiation, who was treated with totalpharyngolaryngo-esophagectomy and total thyroidectomy.Gross examination of the surgical specimen showed agrayish-white, solid, lobulated tumor, mainly locatedbetween the trachea and esophagus, and involving thelower part of the left thyroid lobe. Histologically, the tumorconsisted of epithelial cell nests separated by thick fibroussepta. The tumor cells were polygonal in shape, and con-tained pale cytoplasm and a vesicular nucleus with promi-nent nucleoli. There were few mitotic figures. Rosette-likearrangements that suggested neuroendocrine differentia-tion were observed in part of the tumor. The tumor cellswere positive for CD5 and neuroendocrine markers includ-ing synaptophysin and chromogranin A.
Key words: carcinoma showing thymus-like differentiation,CASTLE, neuroendocrine differentiation
Carcinoma showing thymus-like differentiation (CASTLE) is arare malignant tumor of the neck that histologically resemblesthymic carcinoma.1 Miyauchi et al. first reported three casesof intrathyroidal tumor that resembled primary squamous cellcarcinoma of the thyroid gland but which had a favorableoutcome, as intrathyroidal epithelial thymoma,2 and Chanand Rosai later designated this type of tumor as CASTLE.3CASTLE has been postulated to originate from cervicalectopic thymus or branchial pouch remnants. The majority of
tumors occur in the thyroid gland, usually in the lower portion,but they rarely arise in extrathyroidal soft tissue of the neck.1The histopathology of CASTLE is characterized by an expan-sive growth pattern, thick fibrous bands dividing the tumornests, the presence of lymphocytes, and rare or infrequentmitoses.4 Although, to our knowledge, approximately 30cases of CASTLE have been reported in the English-language literature,217 neuroendocrine differentiation inCASTLE has not been described in detail. We report a caseof CASTLE with neuroendocrine differentiation that waslocated in cervical soft tissue and involved adjacent organs,and which required differential diagnosis from other tumorsderived from the thyroid gland and upper aerodigestive tract.
A 62-year-old Japanese man who had a 6 month history ofcough and sputum consulted a physician, and a lump in hisneck was detected. The patient had never experienced painor dysphagia. He was referred to the Department of Headand Neck Surgery, National Cancer Center Hospital East. CTindicated a well-demarcated cervical mass located on the leftdorsal aspect of the trachea that was connected to the infe-rior portion of the left lobe of the thyroid gland, and thetrachea was displaced to the right (Fig. 1). Radiological evi-dence suggested thyroid cancer. The results of laboratoryexamination were unremarkable. Fine-needle aspirationcytology showed a few clusters of epithelial cells containinglarge nuclei and scant cytoplasm against a clear background,suggesting malignant tumor, but these findings wereinsufficient for cytological evidence indicating papillarythyroid carcinoma or follicular neoplasms. A preoperativeclinical diagnosis of thyroid cancer was made, and totalpharyngolaryngo-esophagectomy combined with total thy-roidectomy was performed and followed by reconstructionwith a free jejunal graft.
Correspondence: Atsushi Ochiai, MD, PhD, Pathology Division,Research Center for Innovative Oncology, National Cancer CenterHospital East, 6-5-1 Kashiwanoha, Kashiwa, Chiba 277-8577,Japan. Email: email@example.com
Received 23 April 2008. Accepted for publication 22 July 2008. 2008 The AuthorsJournal compilation 2008 Japanese Society of Pathology
Pathology International 2008; 58: 775779 doi:10.1111/j.1440-1827.2008.02310.x
Macroscopically the specimen was a grayish-white, solid,lobulated tumor measuring 55 45 40 mm in size that wasmainly located between the trachea and esophagus andinvolved the inferior portion of the left lobe of the thyroid gland(Fig. 2). The tumor protruded into the tracheal lumen in amembranous portion, but was not exposed on the mucosalsurface of the esophagus.
Microscopically, the tumor was composed of epithelial cellnests that were separated by dense fibrous septa (Fig. 3a).The polygonal-shaped tumor cells were arranged in sheetsand there was moderate lymphoplasmacytic infiltration(Fig. 3b). Rosette-like arrangements were observed in part ofthe tumor (Fig. 3c). There were some glandular structurescontaining mucinous material that was positively stained byAlcian blue (pH 2.5)/PAS staining (Fig. 3d). The tumor cells
contained pale cytoplasm, a vesicular nucleus, and promi-nent nucleoli. Apoptotic features were seen frequently, butmitoses were rare (average 1/10 high-power fields). No clearkeratinization or Hassalls corpuscle-like structures wereobserved. There were no histological findings that suggestedtypical thyroid tumor, including papillary carcinoma, follicularadenoma/carcinoma, medullary carcinoma, or undifferenti-ated carcinoma.
The immunohistochemistry results are listed in Table 1.The tumor cells were positive for CD5 (Fig. 3e) and exhibiteda predominantly membranous pattern. Diffuse staining forpan-cytokeratin and high-molecular-weight cyotkeratin(HMWCK) was observed. The tumor cells stained positive forCEA (Fig. 3f) and p63, but were negative for thyroglobulin,thyroid transcription factor-1 (TTF-1) and calcitonin, whichare markers of thyroid-derived tumors. There were smallclusters of tumor cells positive for synaptophysin (Fig. 3g),which accounted for
or trachea. Metastases were found in three of the 17 cervicallymph nodes dissected. The entire specimen was examined,but no ectopic thymic tissue was detected. There was noevidence of recurrence for 5 months after surgery.
We have reported a case of CASTLE that was mainly locatedin the cervical soft tissue between the trachea and esopha-
Figure 3 Histopathology of carcinoma showing thymus-like differentiation (CASTLE). (a) The tumor cell nests are separated by thick fibroussepta. (b) Polygonal tumor cells are arranged in a sheet-like pattern. Many lymphocytes have infiltrated the tumor nest. (c) Rosette-likearrangements and (d) glandular structures are observed in part of the tumor (d, Alcian blue, pH 2.5/PAS staining). Immunohistochemistry for(e) CD5, (f) CEA, (g) synaptophysin, and (h) chromogranin A. Bars: (a) 1 mm; (bh) 50 mm.
2008 The AuthorsJournal compilation 2008 Japanese Society of Pathology
gus. Primary squamous cell carcinoma or undifferentiatedcarcinoma of the thyroid gland, squamous cell carcinoma ofthe upper aerodigestive tract, and metastatic carcinoma fromother organs, in addition to CASTLE were included in thedifferential diagnosis on histopathology. Squamous cell car-cinoma and undifferentiated carcinoma of the thyroid glandwere less probable because clear keratinization is generallyobserved in squamous cell carcinoma of the thyroid glandand cytological pleomorphism is more prominent in un-differentiated carcinoma of the thyroid gland. Moreover,these carcinomas have a more aggressive clinical course.The distinctive growth pattern, lacking a connection with theesophageal mucosa despite extensive involvement of theesophagus by the tumor, ruled out primary esophageal car-cinoma. Metastatic carcinoma was ruled out based on theresults of the systemic examinations. Although the histologi-cal architecture of this CASTLE tumor apparently resembledthat of orthotopic type B3 thymoma, nuclear atypia observedin this tumor was prominent and there was no involvementof CD99-positive immature lymphocytes. CASTLE was firstreported as intrathyroidal epithelial thymoma by Miyauchiet al.2 Chan and Rosai have noted that CASTLE had a morehistological resemblance to thymic carcinoma (so-called typeII malignant thymoma) than thymoma in view of its markednuclear atypia.3
CASTLE tumors are relatively indolent, and grow lessrapidly compared with squamous cell carcinoma of the thy-roid.2 A recent clinicopathological study of 22 patients whounderwent curative surgery found 5 and 10 year cause-specific survival rates of 90% and 82%, respectively.18 Butsome cases involving locoregional recurrence and/or distantmetastasis pursued a rapid fatal course.911 These reportsindicate variation in the malignancy of CASTLE. A meta-analysis suggested that patients with nodal metastasis havea high risk of recurrence.6 Nodal metastasis and extrathyroi-dal extension appear to be predictors of a poorer outcome.18The outcome of orthotopic thymic carcinoma is known to belargely dependent on the histological subtype.19 Tumors with
low-grade histology, such as squamous cell carcinoma andbasaloid carcinoma, have a better prognosis than tumorswith high-grade histology, including lymphoepithelial-like car-cinoma.19 Further investigation is needed to elucidatewhether there are any histological variations in CASTLErelated to the malignancy.
Immunohistochemistry using several markers was helpfulin making the differential diagnosis between CASTLE andother tumors of the thyroid gland and upper aerodigestivetract. CD5 is a surface glycoprotein expressed on mature Tcells and a subset of B cells.20 Thymic carcinoma ce