A ZEBRA IN A STABLE OF HORSES: AN ANTERIOR MEDIASTINAL MASS PRESENTING AS THYMIC CARCINOMA

Nikolas Johs, Marisa Echaniz, , Denver, CO

Meeting: Hospital Medicine 2019, March 24-27, National Harbor, Md.

Abstract number: 742

Categories: Adult, Clinical Vignettes, Hospital Medicine 2019

Case Presentation: Case Presentation: A 65-year-old African-American male with PMH of hypertension and twenty pack-year smoking history presented with eight weeks of substernal chest pain, unintentional weight loss, and occasional night sweats. He noted a constant substernal burning chest pain radiating to left shoulder, without diaphoresis, nausea or vomiting or pleuritic chest pain. His pain was worse with coughing or palpation and did not change with meals. Chest x-ray showed an anterior mediastinal mass, and thoracic CT revealed a 9 x 10 x 11cm mass encircling and compressing the SVC and other great vessels with enlarged paratracheal, subcarinal and hilar lymph nodes. The chest mass was biopsied via VATS procedure. Based on symptoms of weight loss and “B-symptoms”, presumptive diagnosis prior to final pathology results was lymphoma. Pathology results revealed a poorly differentiated, high-grade carcinoma with neuroendocrine features. Immunohistochemical staining for CD117 and CD5 were positive, suggesting a thymic carcinoma. A CT scan of chest and abdomen revealed multiple heterogenous masses in the liver, as well as a left adrenal mass. Final diagnosis was Stage IV thymic carcinoma (T3N3M1). Our patient was started on paclitaxel 225mg/m2 and carboplatin (AUC of 6).

Discussion: Anterior mediastinal mass can represent a number of different pathological and benign conditions. The most important demographic factors when considering the differential are age and gender (1). While thymomas account for about 50% of anterior mediastinal masses in adults, thymic carcinoma is much rarer and represents 5% of thymic neoplasms(2; 3). Patients may present with cough, chest pain, phrenic nerve palsy, or SVC syndrome due to local compressive effect (4). Thymic carcinomas are not typically associated with myasthenia gravis or other paraneoplastic syndromes and are a more aggressive tumor with a generally poorer prognosis. Other considerations include lymphomas and germ cell tumors, also presenting with rapid onset of symptoms, in comparison to thymoma (5).
Local invasion of the mediastinum is common at presentation, hence 5-year survival is low (6). The gold standard is to treat with surgical resection, though up to 2/3 of cases of thymic carcinoma may present with locally invasive disease that is not amenable to surgical resection (4). Patients that present with advanced disease are treated with a multimodal approach of chemotherapy or chemoradiotherapy (4). Given its rarity, large phase III trials have not been conducted to determine optimal treatment regimens; the regimen for our patient was based on a Phase II study examining the efficacy of carboplatin and paclitaxel (7). Anthracycline regimens have been found to be more effective but are also more toxic and therefore not considered for our patient (5).

Conclusions: Conclusion: Thymic carcinoma is a rare cause of anterior mediastinal mass, and carries a poor prognosis compared to benign thymoma.

1. Carter BW et al. 2014 Jour Thorac Oncol
2. Detterbeck et al. 2004 Ann Thorac Surg
3. Venuta F et al. 2010. Eur J Cardiothorac Surg
4. Syrios J et al. 2014. Med Oncol
5. Ettinger DS et al. 2013. J Natl Compr Canc Netw
6. Eng TY et al. 2004. Int J Radiat Oncol Biol Phys
7. Lemma GL, et al. 2011. J Clin Oncol

To cite this abstract:

Johs, N; Echaniz, M. A ZEBRA IN A STABLE OF HORSES: AN ANTERIOR MEDIASTINAL MASS PRESENTING AS THYMIC CARCINOMA. Abstract published at Hospital Medicine 2019, March 24-27, National Harbor, Md. Abstract 742. https://www.shmabstracts.com/abstract/a-zebra-in-a-stable-of-horses-an-anterior-mediastinal-mass-presenting-as-thymic-carcinoma/. Accessed December 5, 2019.

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