Thymic carcinoma: update of current diagnostic criteria and histologic types

Thymic Carcinoma Invading Bilateral Internal Thoracic Artery Bypass Grafts: Diffuse Stenosis Suggesting Extravascular Compression

Thymic carcinoma, a rare but aggressively growing malignancy that tends to invade nearby structures, requires early intervention and is often associated with poor prognosis. A 73-year-old man presented with vague chest pain. Imaging studies coincidently revealed an anterior mediastinal mass invading bilateral internal thoracic artery bypass grafts. Angiography showed diffuse stenosis due to tumor compression and numerous feeding arteries. Positron emission tomography scans led to the clinical diagnosis of thymic carcinoma, stage IVb. We reported an extremely rare and complicated case of unresectable thymic carcinoma invading coronary artery bypass grafts, aiming to discuss the complex features challenging the diagnostic approach and management of the disease. Diffuse stenosis on angiography may suggest extravascular compression by coincident mediastinal tumors. Complicated cases of mediastinal neoplasm with invasion of vital structures require individualized diagnostic approaches and treatment strategies.

Insulinoma-Associated Protein-1 Expression in Lymphoepithelial Carcinoma of the Thymus: A Potential Pitfall for Diagnosis With Neuroendocrine Carcinomas of the Thymus

CONTEXT.—

Insulinoma-associated protein-1 (INSM1) is a recently developed immunohistochemical marker claimed to be highly specific and sensitive for the diagnosis of neuroendocrine malignancies. Recent studies, however, have demonstrated that this marker can also be expressed in non-neuroendocrine neoplasms including squamous cell carcinoma of the thymus.

OBJECTIVE.—

To examine INSM1 expression in lymphoepithelial thymic carcinomas.

DESIGN.—

Thirty-four cases of lymphoepithelial carcinoma of the thymus were examined by immunohistochemistry or in situ hybridization for INSM1, synaptophysin, chromogranin, CD5, CD117, Epstein-Barr virus-encoded small ribonucleic acid (EBER), and Ki-67. Basic clinical information was abstracted from the medical record.

RESULTS.—

The patients were 14 women and 20 men, aged 20 to 85 years. The tumors arose in the anterior mediastinum without any previous history or evidence of malignancy at other sites. Immunohistochemical staining showed moderate to strong positivity of the tumor cells for INSM1 in 65% of cases (22 of 34), focal weak positivity in 20% (7 of 34), and negative staining in 5 cases. Chromogranin staining was focally and weakly positive in 1 case, and synaptophysin showed only focal weak positivity in scattered tumor cells in 12 cases. No significant correlation could be identified between the pattern and intensity of staining for INSM1 and staining for CD5, CD117, and Ki-67.

CONCLUSIONS.—

INSM1 positivity in lymphoepithelial carcinoma of the thymus may represent a pitfall for diagnosis, particularly in small biopsy samples. Awareness of this finding may be of importance to avoid misdiagnosis of neuroendocrine malignancy.

Pleural recurrence 21 years after complete resection of thymic mucoepidermoid carcinoma: a case report

BACKGROUND

Thymic mucoepidermoid carcinomas (MECs) are extremely rare malignant neoplasms. We describe a rare case of a MEC with a high histological grade in a patient who survived for more than 20 years after the initial surgery, focusing on the clinical course and recurrence pattern.

CASE PRESENTATION

A woman underwent surgical resection of a high-grade thymic MEC at another hospital 21 years ago. At the age of 79, she was referred to our hospital with an abnormal opacity incidentally found on her chest radiograph during a health check-up. After the percutaneous biopsy diagnosed thymic MEC, surgical resection was planned based on imaging findings, considering pulmonary metastasis. Intraoperatively, a large tumor and several nodules were detected within the parietal pleura; furthermore, pleural dissemination of the MEC was diagnosed by intraoperative rapid histological evaluation. We completed an exploratory thoracoscopic procedure without performing resection. She did not wish to undergo adjuvant therapy after surgery. Currently, the tumor is growing slowly, but the patient is asymptomatic and is being followed up without treatment intervention.

CONCLUSION

We encountered a rare case of pleural recurrence 21 years after complete resection of thymic MEC. Whether surgical resection, including volume reduction surgery, should be used as a treatment strategy for thymic carcinoma with dissemination requires further discussion.

Clinicopathologic features, tumor immune microenvironment and genomic landscape of EBV-related and EBV-unrelated poorly differentiated nonkeratinizing squamous cell carcinoma of the thymus

OBJECTIVES

Knowledge regarding thymic EBV-related poorly differentiated nonkeratinizing squamous cell carcinoma (PDNKSCC), also known as lymphoepithelial carcinoma (LEC), is extremely limited due to its rarity.

MATERIALS AND METHODS

This multi-institutional study enrolled 85 patients with thymic PDNKSCC. DNA in situ hybridization was performed to evaluate the EBV status of all 85 cases. Immunohistochemistry and next generation sequencing were performed to compare the differences in the clinicopathological and molecular features between EBV-related and EBV-unrelated PDNKSCC. Tumor-infiltrating lymphocytes (TILs) were also analyzed by these methods.

RESULTS

The 85 cases were classified into 27 EBV-related PDNKSCCs (31.8 %) and 58 EBV-unrelated PDNKSCCs (68.2 %) according to the EBV status, and 35 Lymphoepithelioma pattern (LP) (41.2 %) and 50 desmoplastic pattern (DP) (58.8 %) according to the histological characteristics. Compared to the EBV-unrelated PDNKSCC, EBV-related PDNKSCC showed a younger patient predominance and more commonly displayed a LP subtype. Additionally, LP-type cases were divided into two groups: Group 1 (EBV-related, 20/85) and Group 2 (EBV-unrelated, 15/85); the DP-type cases were divided into Group 3 (EBV-unrelated, 43/85) and Group 4 (EBV-related, 7/85). The four Groups showed a significant association with patients' OS and PFS. EBV-related PDNKSCC had significantly higher PD-L1 + tumor cells (TCs) and PD-L1 + and CD8 + immune cells (ICs) than EBV-unrelated PDNKSCC. The tumor microenvironment immune type (TMIT) I (PDL1-Tumor+/CD8-High) was more common in EBV-related PDNKSCC, especially in Group 1(LP and EBV related) with more than 90 % cases belonged to TMIT I. Molecular analysis demonstrated that EBV-related PDNKSCC had a significantly higher tumour mutational burden and frequency of somatic mutations than EBV-unrelated cases.

CONCLUSIONS

EBV-related PDNKSCC, especially the Group 1, could be a candidate for immunotherapy and EBV positivity may provide an indication for the selection of targeted therapy due to their high tumour mutational burden.

Desmoplastic Adamantinoma-like Thymic Carcinoma: Clinicopathologic, Immunohistochemical, and Molecular Study of 5 Cases

Five cases of a heretofore unreported rare variant of thymic carcinoma characterized by a striking resemblance to adamantinoma of the mandible are described. The tumors occurred in 4 women and 1 man aged 58 to 76 years (mean: 67.8 y); they arose in the anterior mediastinum and measured from 5.3 to 12.0 cm in greatest diameter (mean: 8.9 cm). Presenting symptoms included chest pain, shortness of breath, and in 2 patients, pleural effusion. One tumor was asymptomatic and discovered incidentally. Histologically, the tumors were extensively desmoplastic, and the cellular proliferation was characterized by multiple islands of squamous epithelium with striking peripheral palisading of nuclei and central areas containing clear cells resembling a stellate reticulum. Areas of preexisting spindle cell thymoma were identified in 2 cases; these areas gradually merged with the higher-grade component of the lesion. Cystic changes were noted in 3 cases. Immunohistochemical studies in 3 cases showed the tumor cells were positive for cytokeratins, p40 and p63, and all showed a high proliferation rate (>50% nuclear positivity) with Ki-67. Next-generation sequencing was performed in 2 cases that showed amplification of the AKT1 gene (copy numbers 6 and 13). Clinical follow-up in 3 patients showed recurrence and metastasis after 1 and 2 years; 1 patient passed away 2 years after diagnosis due to the tumor. Desmoplastic adamantinoma-like thymic carcinoma represents an unusual histologic variant of thymic carcinoma that needs to be distinguished from metastases from similar tumors to the mediastinum.

Dissolution of metastatic thymic carcinoma-associated right atrial thrombus with rivaroxaban

Thymic carcinoma typically exhibits more clinically aggressive behavior and portends a worse prognosis as compared to thymoma. Venous thromboembolism is a significant cause of morbidity and mortality in oncologic patients. Traditionally, the standard-of-care management of cancer-associated venous thromboembolism has been therapeutic anticoagulation with low molecular weight heparins; however, with the advent of direct oral anticoagulants, there is an ongoing paradigm shift to transition to these novel agents in an attempt to attenuate cancer-associated venous thromboembolism events. We describe an exceedingly rare case of metastatic thymic carcinoma-associated right atrial thrombus with high-risk embolic features, which subsequently underwent near-complete dissolution with rivaroxaban after 3 months.

The role of needle core biopsies in the evaluation of thymic epithelial neoplasms

Thymic epithelial neoplasms are rare tumors derived from thymic epithelium that most often present as large anterior mediastinal masses. The vast majority of thymic epithelial neoplasms fall under the diagnostic category of thymoma, with a smaller percentage qualifying for a diagnosis of thymic carcinoma. The ability to render a definitive diagnosis on these tumors is generally hampered by their deep location and close proximity to vital structures, which makes biopsy sampling for histopathologic evaluation difficult. In recent years, the trend in medicine has been to opt for the least invasive procedure to obtain tissue samples that, by definition, implies also obtaining smaller and smaller biopsies, resulting in lesser amounts of tissue available for examination. In the mediastinum, the most common modalities for procuring biopsy samples from mass lesions include fine-needle aspiration, percutaneous core needle biopsy and video-assisted thoracoscopic biopsy. In this review, we will deal only with the role and limitations of percutaneous core biopsies in the interpretation of thymic epithelial neoplasms.

Morphological spectrum of mediastinal lesions with special emphasis on evaluation of needle biopsy: An experience from a tertiary care hospital

Background & objectives:

Mediastinal lesions are uncommon and are infrequently encountered in routine clinical practice. Hence, there is a need for more elaborate studies of mediastinal lesions to make the pathologists and clinicians aware of the large spectrum of these lesions. The present study describes the histomorphological spectrum of various mediastinal lesions in a tertiary care hospital in India, along with the discussion of some unusual and interesting cases. Considering the limited diagnostic material obtained in guided biopsies, the adequacy of such tissue for providing a definite opinion was also evaluated.

Methods:

This was a retrospective study performed on 125 mediastinal masses diagnosed on surgically resected specimens as well as needle biopsies over a period of two years (January 2012-December 2013). A few cases had inadequate diagnostic material, making a total of 116 cases which were further evaluated.

Results:

A total of 116 patients of mediastinal lesions were included in the study. Most of the lesions were in 21-30 yr age group, with male:female ratio of 1.7:1. Anterior mediastinal compartment was most commonly involved. Majority of the cases (62.1%) were of neoplastic nature, with benign tumours (34.5%) being more common than malignant ones (27.6%). Thymoma followed by lymphoma constituted the most common mediastinal tumours. One-third of the total cases were diagnosed on needle biopsy samples. All cases where needle biopsy was followed by resection specimen showed concordant diagnosis. The percentage adequacy of biopsy was 91.7 per cent and the diagnostic accuracy was 100 per cent.

Interpretation & conclusions:

This study provides the histomorphological spectrum and biological diversity of the mediastinal lesions. It also emphasizes that biopsy is sufficiently adequate, with the help of a comprehensive immunohistochemistry panel, for providing a definite diagnosis in majority of cases.

About thymic carcinomas: challenges in diagnosis and management

BACKGROUND

Thymic carcinomas are rare tumors with a challenging diagnosis. Our aim was to report our 17-year experience of these tumors and to highlight the challenges encountered and the main differential diagnoses ruled out.

METHODS

We studied 12 (92%) men and 1 (7.7%) woman with a mean age of 37 years (range 15-60 years). All patients were symptomatic, with chest pain representing the most frequent symptom. Radiology revealed anterior mediastinal masses in all cases, with either infiltration of the adjacent organs or pulmonary parenchymal metastases.

RESULTS

The diagnosis was made on surgical biopsies in 12 cases and a lymph node biopsy in one. Microscopic examination revealed squamous carcinoma in 3 cases, synovial sarcoma in 1, mucinous adenocarcinoma in 1, undifferentiated carcinoma in 2, clear cell carcinoma in 1, lymphoepithelioma-like carcinoma in 2, atypical carcinoid tumor in 2, and sarcomatoid carcinoma in 1. Total surgical resection was possible in one patient after neoadjuvant chemotherapy and radiotherapy. Follow-up was possible in only 6 patients, and the mean survival reached 13 months.

CONCLUSION

In spite of the lack of follow-up information, this study demonstrates the poor outcome associated with these tumors and the need for standardized treatment.

Spinal metastasis of thymic carcinoma as a rare manifestation: a summary of 7 consecutive cases

BACKGROUNDS

Thymic carcinomas are very rare tumors that are often associated with extrathoracic metastasis to other organs. However, it is well known that thymic carcinomas rarely metastasize to the spine, and the prognosis, treatment, and natural course of this disease are not yet standardized.

METHODS

We describe seven thymic carcinoma patients with spinal metastasis who were diagnosed and treated in our institute from January 2006 to December 2011. We performed surgical treatment and adjuvant chemotherapy and/or radiation therapy, in consideration of each individual disease's course, and we regularly followed up the patients.

RESULTS

Of the seven patients, five were male and two were female. Six had metastases in the thoracic spine, and one had metastases in the lumbar spine. An extradural lesion was found in five patients, and two patients had both extradural and intradural lesions. The period from the primary diagnosis to spinal metastases varied widely (range, 1.23-14 years). After surgery, all patients showed an improvement of back pain and radicular pain. Two patients were lost to follow-up, but the other five maintained ambulatory function until their final follow-up. Four patients died because of pulmonary complications accompanied with the disease's progression. One patient died from uncontrolled brain metastases. After surgery, the median survival was 204±111.43 days.

CONCLUSION

Because metastasis to the spine from thymic carcinoma is very rare, there are no treatment guidelines. Nevertheless, we suggest that appropriate surgical management of the metastatic lesion is necessary for the preservation of the patient's quality of life during survival.

Primary thymic mucinous adenocarcinoma: a case report

Primary thymic mucinous adenocarcinoma is an extremely rare aggressive subtype of thymic carcinoma. With a review of literatures, only nine cases have been reported up to present. A 36-year-old woman was admitted for further evaluation and treatment of a mediastinal mass. The patient had no medical history of cancer. The clinicoradiological examination disclosed no tumor elsewhere. After the surgical excision of mediastinal mass, it was grossly a round semi-solid mass with mucin-filled cystic areas. Microscopically solid areas showed cords, small nests and dilated glands infiltrating the fibrotic parenchyma, while the cystic areas were lined by mucinous epithelium with tumor cells floating in extracellular-mucin pools. Some cystic walls underwent malignant transformation of the benign thymic epithelium. Immunohistochemically, the tumor cells were positive for cytokeratin (CK) 7, CK20, CD5, and CDX-2, and negative for thyroid transcription factor-1. In conclusion, the mucinous thymic adenocarcinoma should be recognized as a separate histopathological entity and considered in the differential diagnosis of mediastinal carcinomas.

Micronodular thymic carcinoma with lymphoid hyperplasia: a clinicopathological and immunohistochemical study of five cases

Five cases of an unusual variant of thymic carcinoma are described, which represent the counterpart of the so-called micronodular thymoma with lymphoid hyperplasia. The patients were three men and two women aged 42-78 years (mean 64 years). Three patients were asymptomatic and the tumors were found incidentally on chest radiographs performed for unrelated reasons. Two patients complained of dyspnea, chest pain and shortness of breath prompting further investigations. The tumors ranged in size from 3.2 to 10.0 cm and were described as infiltrative masses often invading adjacent structures. Prominent cystic changes were not identified. Histologically, the neoplasms were composed of epithelial tumor cells arranged in a micronodular growth pattern set in a stroma showing florid lymphoid hyperplasia. Contrary to micronodular thymoma, the epithelial cell component of the present cases showed unequivocal signs of malignancy characterized by cytological atypia and increased mitotic activity. Immunohistochemical studies showed the lymphoid component to be of mixed B- and T-cell lineage. None of the patients had a history of myasthenia gravis or other autoimmune disorder. Follow-up revealed that 4 patients were alive and well 3-26 months after diagnosis while 1 patient was dead of disease 21 months after diagnosis. The tumors in this series represent a distinct subtype of thymic carcinoma histologically strongly resembling micronodular thymoma with lymphoid hyperplasia. Awareness of this type of thymic carcinoma is important in order not to dismiss this tumor for a neoplasm of lower-grade malignancy.

Thymic papillo-tubular adenocarcinoma containing a cyst: report of a case

We report a case of thymic papillo-tubular adenocarcinoma in a 55-year-old man, who had no symptoms. Sternotomy revealed a tumor in the anterior mediastinum, tightly adhered to the pericardium. It was resected completely. Interestingly, the tumor contained a unilocular cyst filled with mucinous fluid, suggesting that it originated from a pre-existing thymic cyst. Pathological examination of the tumor revealed a primary thymic papillo-tubular adenocarcinoma resembling a tumor of gut origin. Thymic adenocarcinomas, particularly of the tubular subtype, are extremely rare.

Metaplastic thymoma: report of 4 cases

Metaplastic thymoma (MT), accepted in the World Health Organization 2004 scheme, is a circumscribed tumor of the thymus exhibiting biphasic morphology. We herein describe the clinicopathologic features of four MTs and the differential diagnoses of this unusual tumor. There were three women and one man with mean age of 49.5 years. The patients were found to have mediastinal masses, and underwent surgical excision. One exhibited symptoms of myasthenia gravis, and the serum titer for anti-acetylcholine receptor antibody was positive. Grossly, the tumors were encapsulated, and showed vaguely multinodular, solid, tan-white to yellow cut surfaces. Histologically, they comprised epithelial islands intertwining with bundles of delicate spindle cells. The patients remained well after surgical excision at 5-55 months. Because of the distinctive histological appearance and benign clinical course, MT should be distinguished from other more aggressive mediastinal neoplasms displaying biphasic feature.

[Lymph node supraclavicular metastasis of thymic carcinoma: an inaugural and unusual feature of a rare disease]

Among the epithelial tumours of the thymus, thymic carcinomas are rare, involving more aggressive locoregional behaviour and a poor prognosis. More than one-third of cases present lymph node metastasis during an evaluation of the extension of a primitive mediastinal tumour of thymic origin. The authors report an unusual case in a 46-year-old woman presenting a metastatic form. The diagnosis of epidermoid thymic carcinoma was based on the histopathological examination of a right supraclavicular lymph node, associated with an anterior radiological mediastinal tumoral syndrome, raising the delicate problem of its diagnosis and treatment.

Establishment, characterization and drug sensitivity testing in primary cultures of human thymoma and thymic carcinoma

Thymomas and thymic carcinomas are peculiar epithelial tumors of the anterior mediastinum. They may show aggressive clinical behavior and are a paradigm for the interaction between the tumor and the immune system. So far, adequate functional studies enabling a better understanding of this malignancy have not been performed, since human thymoma/thymic carcinoma cell lines have not been available. Here, the authors describe the establishment, characterization and functional analyses of epithelial cell lines from a Type B1-thymoma and a poorly differentiated thymic carcinoma. By Fluorescence-activated cell sorting (FACS) analyses, both cell lines were aneuploid. The aneuploid cell fraction of the thymic carcinoma cell line was characterized by a high proliferation index of 55.9%, in contrast to a lower proliferation rate of the aneuploid cell fraction of the thymoma (19.7%). Array-based comparative genomic hybridization (aCGH) and conventional cytogenetic analysis of the thymoma revealed only minor imbalances whereas the thymic carcinoma was characterized by a complex karyotype in the hyperdiploid range that was readily defined with multicolor FISH (mFISH). Application of a selective COX-2 inhibitor reduced cell viability in both cell lines in a dose-dependent manner. In conclusion, these first cell lines of a thymoma and a CD5-positive thymic carcinoma are useful tools for further in vitro studies of cellular, molecular and genetic aspects of the disease and for functional tests to evaluate new therapeutic targets.

Papillary adenocarcinoma of the thymus: case report and review of the literature

A 44-year-old male with a mediastinal mass measuring 3.5 × 3.5 × 3 cm was diagnosed with papillary adenocarcinoma of the thymus. Other origins of papillary adenocarcinoma were excluded by clinical, imaging, and immunocytochemical methods before assuming this diagnosis. Residual thymus was seen under the microscope. Focal CD5 immunoreactivity was present. There was no associated thymoma. The patient underwent surgery, radiotherapy, and chemotherapy. He disclosed systemic recurrence at 18 months (subcutaneous nodule). He is alive after 24 months of follow-up with active disease. There had been only 7 cases of this rare entity published before.

Mucinous adenocarcinomas of the thymus: report of 2 cases and review of the literature

BACKGROUND

Most adenocarcinomas of the mediastinum are metastatic lesions. Primary thymic adenocarcinomas are extremely rare neoplasms. We could find only 12 cases reported in the literature; of these 12, only 4 were of the mucinous subtype.

DESIGN

We report 2 additional cases of the mucinous subtype, including a previously unreported mucinous variant with numerous psammoma bodies.

RESULTS

The first case in a 61-year-old woman resembled a mucinous (colloid) carcinoma of other organs such as the breast and colon. It consisted of islands and strips of tumor cells floating in large pools of extracellular mucin. A unique feature of this tumor was the presence of numerous psammoma bodies. Immunohistochemically, the tumor cells were positive for cytokeratin (CK) 7 and negative for CD5. The second case in an 82-year-old woman was a mucinous adenocarcinoma arising from a thymic cyst with areas of transition from benign to dysplastic epithelium. The tumor cells formed dilated glands, cords, and small nests that infiltrated the thymic cyst wall and exhibited evidence of mucin production. Immunohistochemically, the tumor cells were positive for CK 7 and focally positive for both CD5 and CK 5/6.

CONCLUSIONS

Mucinous adenocarcinoma, with or without, psammoma bodies, may be of primary thymic origin and should be considered in the differential diagnosis of malignant mediastinal tumors. These 2 cases provide further documentation of the rare occurrence of primary mucinous adenocarcinomas of the thymic gland.