Thymic atypical carcinoid tumors with elevated mitotic counts in a patient with multiple endocrine neoplasia: A case report

Thymic neuroendocrine tumors associated with multiple endocrine neoplasia are only defined as carcinoid and are not associated with large-cell neuroendocrine carcinoma (LCNEC). We report the case of a multiple endocrine neoplasia type 1 patient with atypical carcinoid tumors with elevated mitotic counts (AC-h), an intermediate condition between carcinoid and LCNEC. A 27-year-old man underwent surgery for an anterior mediastinal mass and was diagnosed with thymic LCNEC. Fifteen years later, a mass appeared at the same site, which was determined to be a postoperative recurrence based on the pathological results of a needle biopsy and the clinical course. The patient's disease remained stable for 10 months on anti-programmed death-ligand 1 antibody and platinum-containing chemotherapy. The needle biopsy specimen was submitted for next-generation sequencing, which revealed a MEN1 gene mutation, and after further examination, a diagnosis of multiple endocrine neoplasia type 1 was made. A re-examination of the surgical specimen from 15 years prior showed that it corresponded to AC-h. Although thymic AC-h is classified as thymic LCNEC according to the current definition, our data suggests that a search for multiple endocrine neoplasia is warranted in such patients.

Long-term Treatment With Metyrapone in a Man With Ectopic Cushing Syndrome

This is a unique case of ectopic adrenocorticotropic hormone (ACTH)-secreting mediastinal neuroendocrine tumor, presumably thymic in origin, with suspected lung metastasis in a 61-year-old man who was successfully managed with long-term metyrapone alone. He presented with severe hypokalemia and hypertension, complicated with psychosis and vertebral collapse. He survived through a complicated course of pulseless ventricular tachycardia arrest and a severe Cushing storm due to drug nonadherence. For 3 years since diagnosis, he remained stable on metyrapone, and was able to achieve biochemical eucortisolism, with normalization of ACTH and cortisol levels. In addition, his tumor was reduced in size and the suspicious lung metastasis regressed.

Early Detection of Relapse by ctDNA Sequencing in a Patient with Metastatic Thymic Tumor and MEN1 Mosaicism

CONTEXT

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disease caused by inactivating mutations in the MEN1 gene. In the literature, few cases of MEN1 have been reported because of mosaic MEN1 mutations.

OBJECTIVE

We performed an extensive molecular characterization in several lesions and blood samples, including plasmatic circulating cell-free DNA (ccfDNA) in an exceptional case of a patient with MEN1 mosaicism causing primary hyperparathyroidism, multiple pancreatic neuroendocrine tumors (NETs), and a metastatic thymic NET.

METHODS

Blood, ccfDNA and multiple tissue analysis were performed by next-generation sequencing.

RESULTS

MEN1 mosaicism was confirmed by multiple tissue analysis. Somatic analysis of the largest pancreatic NET revealed the same MEN1 second-hit mutation as found in the thymic lesion, demonstrating its metastatic origin from the thymic lesion. Moreover, in ccfDNA we found the mosaic MEN1 mutation but also the somatic second-hit mutation found in the thymic primary tumor, revealing the presence of circulating tumor DNA (ctDNA). After surgical removal of the pancreatic metastasis, the mutated fraction of both mutations decreased, before increasing again several weeks before a new clinical relapse, suggesting that thymic ctDNA may be used as an early tumor biomarker.

CONCLUSION

This exceptional MEN1 case highlighted (1) the importance of looking for MEN1 mosaicism, (2) that MEN1 mosaicism can cause very aggressive disease, and (3) the interest in analyzing ccfDNA for confirming MEN1 mosaicism but also as a potential tumor biomarker for NET.

Correlation of Somatostatin Receptor 2 Expression, 68Ga-DOTATATE PET Scan and Octreotide Treatment in Thymic Epithelial Tumors

Somatostatin receptor 2 (SSTR2) has been shown to be expressed in a subset of neuroendocrine tumors and carcinomas and plays a role in imaging studies and guiding therapy. Patients with tumors expressing SSTR2 may be successfully treated with somatostatin inhibitors or radiolabeled somatostatin analogues. We studied SSTR2 expression in TET and correlated it with 68Ga-DOTATATE PET/CT or 68Ga-DOTATATE PET/MR results and treatment outcome. An institutional database of TET was searched for thymoma, thymic carcinoma, and thymic neuroendocrine tumor (TNET) with available resection specimens. Cases were subtyped (2021 WHO classification) and staged (8^th AJCC/UICC staging). A section was stained with anti-SSTR2 antibody (clone UMB1). Percent tumor cells with membranous staining was recorded if present in ≥1% of tumor cells. Medical records were searched for 68Ga-DOTATATE PET scans and treatment. Statistical analysis was performed. Eighty patients (1969-2021) with a median age of 61.3 years (range, 19.1-87.3) (37 males, 46.3%) had thymic carcinoma (N=33), TNET (N=7), or thymoma (N=40). SSTR2 expression was identified in 29 (of 80, 36.3%) TET including 2/2 (100%) small cell carcinomas, 2/5 (40.0%) atypical carcinoid tumors, 16/23 (69.6%) squamous cell carcinomas, 2/2 (100%) lymphoepithelial carcinomas, 1/1 (100%) adenosquamous carcinoma, and 6/40 (15.0%) thymomas. SSTR2 expression in ≥50% of tumor cells (vs 1-49%) was associated with younger age (p=0.023) and shorter recurrence/metastasis-free survival (p=0.007). 68Ga-DOTATATE PET scans (N=9) revealed a Krenning score of 3 in patients with atypical carcinoid tumor, small cell carcinoma, and squamous cell carcinoma (N=1 each) with SSTR2 expression in 95, 100, and 5% of tumor cells, respectively. Scans with Krenning scores of ≤2 (N=5) were seen in tumors with no SSTR2 expression in 80% of cases and a single atypical carcinoid tumor with SSTR2 expression in 10% of tumor cells. One scan resulted as "increased uptake" was in a patient with no SSTR2 expression. In conclusion, 68Ga-DOTATATE PET scans correlated with SSTR2 expression in TET in most patients and appeared to be useful to identify patients with TET who may be amenable to treatment with somatostatin analogues. Larger studies including more patients with 68Ga-DOTATATE PET scans are necessary to independently and prospectively validate our findings.

Juan Rosai

Throughout his career, Dr. Juan Rosai greatly impacted our understanding of mediastinal tumors, both as a scientist and as a teacher. This review highlights his manifold contributions in the field of thymic carcinomas and thymic neuroendocrine tumors from a historical perspective.

Multidisciplinary treatment of thymic neuroendocrine tumors: surgery remains a key component

BACKGROUND

Thymic neuroendocrine tumors (NETs) are rare malignancies often treated in a multidisciplinary fashion. However, evidence for adjunctive therapy is limited, and predictors of survival and recurrence are not well established.

METHODS

Patients treated for thymic NETs at a single center from 1975 to 2018 were reviewed. Variables collected pertained to tumor factors, stage, and treatments, including surgery. Univariate and multivariate regression analyses were used to determine predictors of overall survival (OS) and recurrence.

RESULTS

We identified treated 49 patients, among whom 36 (73%) were male with a median age of 46 years. Surgical resection was pursued in 41 (84%) patients, and chemotherapy and radiation therapy were used in 27 (55%) and 21 (43%) instances as either neoadjuvant, adjuvant, or definitive therapy. Median tumor size was 6.5 centimeters and most tumors were intermediate-grade. During a median follow-up time of 60.8 months following surgical resection, disease recurrence was observed in 29 (71%) patients and median survival time was 83.7 months. In Kaplan-Meier analysis for survival, surgical resection was associated with a longer survival time (P=0.002), while receipt of neoadjuvant therapy was associated with poorer survival. Larger tumor size was associated with recurrence following resection (P=0.047).

CONCLUSIONS

Thymic NETs represent a heterogeneous disease with variable survival. While we are unable to report clear evidence that supports the use of adjunctive therapies, surgery is important to survival. Additionally, it is likely that those receiving induction chemotherapy represent a unique cohort with advanced or aggressive disease. Among surgical candidates, tumor size predicts disease recurrence.

Surgical treatment of ectopic adrenocorticotropic hormone syndrome with intra-thoracic tumor

BACKGROUND

The study was to review the clinical manifestations and laboratory examinations of ectopic adrenocorticotropic hormone (ACTH) syndrome, and to analyze the efficacy of surgical treatment.

METHODS

The clinical data, surgical therapy, and outcome of 23 cases of ectopic ACTH syndrome accompanied by intra-thoracic tumors were reviewed. The tumors were removed from all the patients according to the principles of radical resection.

RESULTS

The tumors were confirmed as associated with ectopic ACTH secretion in 19 cases. Hyperglycemia and hypokalemia were recovered, while plasma cortisol, plasma ACTH and 24-hour urinary free cortisol (UFC) levels were significantly reduced after surgery in these 19 cases. Recurrences of the disease were found in six cases during following-up, and five of them died.

CONCLUSIONS

The thoracic cavity should be a focus in routine examinations of patients with symptoms of Cushing's syndrome (CS), because ectopic ACTH-producing tumors are commonly found in bronchus/lung and mediastinum. Despite the incidence of the pulmonary nodule secondary to opportunistic infection in some cases, surgery is still the first choice if the tumor is localized. The surgical procedure should be performed according to the principles in resection of lung cancer and mediastinal tumor. The surgical efficacy is significant for short-term periods; however, the recurrence of the disease in long-term periods is in great part related to distal metastasis or relapse of the tumor.