Thymic Carcinoma with Adenoid Cystic Carcinomalike Features with Distant Metastases

Primary thymic adenoid cystic carcinoma with high-grade transformation: A clinicopathological and immunohistochemical analysis of 4 cases

Four cases of a distinct carcinoma of the thymic gland are presented. The patients were 4 adult males with an age range from 40 to 47 years (mean, 43.5 years). Clinically, all patients presented with non-specific respiratory symptoms. None of the patients had any prior history of head and neck neoplasm or surgery in that anatomic area. Large anterior mediastinal masses were found on diagnostic imaging with concurrent metastatic disease to pleura, lungs, regional lymph nodes and bones. Microscopically, all tumors were composed of a solid proliferation of hyperchromatic, monomorphic small cells with focal cytoplasmic clearing embedded in a fibromyxoid stroma. In one case, occasional duct-like structures were identified. Immunohistochemically, the tumors were positive for pancytokeratin, CD117 and MYB and negative for myoepithelial markers. Systemic chemotherapy was initiated in all patients. Despite therapy, clinical follow-up revealed that all 4 patients died of their disease 11-23 months after their initial diagnosis. The cases in this series highlight a tumor that is different from conventional thymic carcinoma and that has the morphological and immunohistochemical features commonly seen in adenoid cystic carcinomas with high-grade transformation. Correct diagnosis is essential for patient management.

Adenoid cystic carcinoma of the thymus gland

BACKGROUND

Thymic carcinomas are rare and aggressive tumours. They constitute a heterogeneous group of tumours with various histological patterns and subtypes resembling epithelial tumours arising from other organs.

CASE PRESENTATION

We hereby represent a case of primary thymic carcinoma with adenoid cystic carcinoma-like features (TCACC) which is an extremely rare variant of thymic adenocarcinoma. To date and to the best of our knowledge, there are nine reported cases in literature and ours is the tenth. Our case was treated surgically but the implementation of adjuvant chemoradiotherapy has been reported in few of the published cases.

CONCLUSIONS

TCACC constitutes a rare entity of thymic adenocarcinoma with limited available literature. The current data is derived from few case reports and case series. The histological overlap of these tumours and primary ACC of salivary glands poses a diagnostic challenge. Radiological investigations, immunohistochemical phenotyping and genetic analysis are crucial in establishing the diagnosis.

Primary thymic carcinoma with adenoid cystic carcinoma-like features: A case report and literature review

RATIONALE

Thymic carcinoma with adenoid cystic carcinoma-like features is a special subtype of thymic adenocarcinoma, and the occurrence of this condition is extremely rare. Herein, we report a case of primary thymic carcinoma with adenoid cystic carcinoma-like features in a young man.

PATIENT CONCERNS

A 38-year-old man had an incidental finding of space-occupying lesion in the anterior mediastinum during a routine health examination. The patient complained of occasional mild chest tightness during hot weather but had no obvious cough, sputum, chest pain, or fever. Contrast-enhanced computed tomography scan of the chest revealed a space-occupying lesion in the anterior mediastinum, which is likely benign.

DIAGNOSIS

The lesion was diagnosed as a primary thymic carcinoma with adenoid cystic carcinoma-like features.

INTERVENTION

The patient underwent thoracoscopic resection of left anterior mediastinal mass and enlarged resection of thymectomy and mediastinal fat in our hospital.

OUTCOMES

The postoperative course was uneventful.

LESSONS

The tissue characteristic of this tumor was extremely similar to that of adenoid cystic carcinoma. A precise pathological examination is extremely important to prevent misdiagnoses of the lesion as adenoid cystic carcinoma or other thymic tumors. Immunohistochemical staining is extremely useful for the pathological and differential diagnoses of this tumor.

Primary Salivary Gland Type Tumors of the Thymus

The existence of primary salivary gland type tumors (SGTs), similar to those occurring in the major salivary glands, is well known in the thoracic cavity. When they occur in this anatomic area, these tumors more commonly arise from the lung. However, the existence of these tumors primarily affecting the thymus, although recognized in the literature, is rather not well documented or known. In addition, contrary to the primary lung SGTs, which are predominantly of the malignant type, these tumors when occur in thymus encompass a wider spectrum of biology ranging from benign to low grade, and high grade malignancy. The recognition of SGTs in the thymus, even though rare, is important to properly address treatment and prognosis. Herein, we will discuss the numerous benign a malignant SGTs that have been described in the thymus and highlight the difficulty that these tumors may pose when occurring in the thymic area.

Pleuromediastinal Epithelial-Myoepithelial Carcinomas: A Clinicopathologic and Immunohistochemical Study of Two Cases

OBJECTIVES

Two cases of epithelial-myoepithelial carcinoma are presented, one arising in the pleura and the other in the anterior mediastinum. The cases represent a unique distribution of these tumors within the thoracic cavity.

METHODS

Both patients were men aged 25 and 68 years, respectively, who had chest pain and dyspnea. Imaging revealed an anterior mediastinal mass in one patient and a pleural-based tumor in the other. Neither patient had any history of malignancy, and physical examination did not disclose any tumor elsewhere.

RESULTS

Initial biopsy specimens were inconclusive, and final diagnosis was deferred to surgical resection performed via median sternotomy and thoracotomy, respectively. Histologically, the lesions were characterized by epithelial and myoepithelial elements distributed as discrete tubules or duct-like structures or sheets of neoplastic cells. Immunohistochemistry showed positive staining for cytokeratin and epithelial membrane antigen in the epithelial component, while S100 protein and smooth muscle actin were expressed in the myoepithelial elements. Follow-up showed that both patients were alive 6 and 12 months after surgery, respectively.

CONCLUSIONS

These cases highlight the ubiquitous distribution of salivary gland-type tumors in the thoracic cavity. These tumors should be included in the differential diagnosis of thoracic neoplasms also in locations other than the lung.

Histologic characteristics of thymic adenocarcinomas: Clinicopathologic study of a nine-case series and a review of the literature

Primary thymic adenocarcinoma is an extraordinarily rare malignancy; only 49 cases have been reported in the medical literature to date. Because of its rarity, clinical and pathologic characteristics of thymic adenocarcinoma are unclear. We present nine cases of primary thymic adenocarcinoma and discuss clinicopathologic findings in the context of the existing literature. Two-hundred twenty-six thymic carcinoma cases were diagnosed at Samsung Medical Center in Korea, from January, 2001 to July, 2016. Nine of these 226 cases were primary thymic adenocarcinomas. The mean age of primary thymic adenocarcinoma patients was 53.6 years, slightly younger than the mean age of patients with thymic squamous cell carcinomas. The male to female ratio was 2:1. Symptoms, if present, were usually due to compression by the tumor. Tumors showed an extra- or intra-cellular mucin and tubular growth pattern, with CK20- and CDX2-immunoreactivity, similar to adenocarcinomas of the lower intestinal tract. Twenty-five previously reported cases, classified as mucinous adenocarcinoma and adenocarcinoma, not otherwise specified, also had similar characteristics to enteric-type adenocarcinoma and generally expressed CK20, CDX2, CEA, and/or MUC2. Some of these cases had a thymic cyst. These characteristics are different from those of papillary thymic carcinomas, which are morphologically similar to papillary thyroid carcinomas, express CK7 but not CK20, and are often associated with thymoma. The prognosis of thymic adenocarcinoma, enteric type appeared to be worse than the prognosis of papillary thymic carcinoma or carcinoma with adenoid cystic carcinoma-like features. In summary, we demonstrated that common primary thymic adenocarcinomas show enteric-type differentiation with mucin. This tumor type has distinct clinical, pathological, immunohistochemical and prognostic characteristics and is different from other subtypes of thymic adenocarcinoma, papillary thymic carcinoma, and carcinoma with adenoid cystic carcinoma-like features.

Thymic Tumor With Adenoid Cystic Carcinoma-Like Features: A Study of a Clinically Favorable Case Followed for 9 Years

Thymic tumors with adenoid cystic carcinoma-like features are true rarities, with only 6 cases reported. Our knowledge of their clinical behavior is insufficient. We present a case of a noninvasive cribriform tumor that was followed, including a 4-year period after tumor resection and radiation therapy, for a total of 9 years. The tumor was purely epithelial. It was positive for keratins (AE-1/AE-3, CK19, 34βE12,CK5/6), MOC-31, P63, P40, CD10, and MYB, and was negative for myoepithelial or neuroendocrine markers. Presence of cell processes, desmosome-like junctions with tonofilaments and multifocally reduplicated basal lamina was noted on ultrastructural examination. Two signals of the MYB gene per cell were detected by fluorescence in situ hybridization. No monosomy or translocations of the gene were found. Although additional clinical studies are necessary, it seems that indolent behavior of cribriform noninvasive subset of these tumors may be anticipated.

Adenocarcinoma of the thymus, enteric type: report of 2 cases, and proposal for a novel subtype of thymic carcinoma

We report 2 cases of primary thymic adenocarcinoma with enteric differentiation. One carcinoma occurred in a 41-year-old man as a 7-cm-diameter cystic tumor and the other one in a 39-year-old woman as a 6-cm-diameter solid mass. Both tumors were located in the anterior mediastinum. Clinical staging did not reveal any extrathymic tumor. Histologically, the tumors were classified as adenocarcinoma, not otherwise specified, and a mucinous (colloid) carcinoma, respectively. Immunohistochemically, both tumors were positive for cytokeratin 20 (CK20), CDX2, and carcinoembryonic antigen, reflecting enteric differentiation. A review of the literature on 43 other cases of primary thymic adenocarcinomas suggested 11 further cases with enteric differentiation, as assessed by CK20 and/or CDX2 expression. We propose that thymic adenocarcinoma with enteric differentiation represents a novel subtype of thymic carcinoma. It is mostly of mucinous morphology and frequently associated with thymic cysts. The clinical outcome is variable. Recognition of primary thymic adenocarcinoma with enteric differentiation is helpful for the differentiation from metastatic disease, mainly from the gastrointestinal tract.