대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Large cell neuroendocrine carcinoma (LCNEC) of the thymus

Radiologic Findings

Chest radiography (Fig. 1) showed relatively well defined large mass in left central area, obscuring left heart border. Non-enhanced (Fig. 2) and enhanced chest CT scan (Fig. 3-5) showed a well-defined, lobulated, inhomogeneously enhancing mass in left side of anterior mediastinum, abutting pulmonary trunk, left main pulmonary artery, left aspect of aortic arch, left upper pulmonary vein. A satellite small well defined nodule was located between left common carotid artery and left brachiocephalic vein (Fig. 6). showed no evidence of lung parenchymal invasion. PET-CT scan showed heterogenous high FDG uptake in the mass lesion (SUVmax: 8.19, Fig. 7).
The patient underwent surgical mass excision (Fig. 8). The final pathological report showed a large cell neuroendocrine carcinoma (LCNEC) of the thymus. The tumor cells were immunoreactive for the neuroendocrine markers cytokeratin-Pan, synaptophysin, and CD56 on the immunohistochemical stains.

Brief Review

Primary thymic neuroendocrine carcinomas (NECs) are relatively rare neoplasms that may account for approximately 2%–4% of all anterior mediastinal neoplasms. NECs were morphologically categorized into four main types: typical carcinoid, atypical carcinoid, large cell neuroendocrine carcinoma (LCNEC), and small-cell carcinoma.
A LCNEC of the thymus is a very rare malignant tumor which has a very poor prognosis.
There were a few case reports of LCNEC of the thymus.
A thymic NET typically manifests as a large, lobulated, usually invasive, anterior mediastinal mass with heterogeneous enhancement that may exhibit areas of hemorrhage and necrosis. Punctate and dystrophic calcifications may also be seen. There are no pathognomonic findings, and it may be difficult to distinguish a thymic NET from other thymic malignancies or from nonthymic malignancies such as lymphoma or metastatic disease on the basis of radiographic imaging.
LCNEC was characterized by 1) a light microscopic neuroendocrine appearance, 2) large sized, polygonal-shaped cells having a low nuclear-cytoplasmic ratio with coarse nuclear chromatin and frequent nucleoli, 3) a high mitotic rate greater than 10/10 high power fields, and frequent necrosis, and 4) neuroendocrine features by immunohistochemistry or electron microscopy.
Surgery offers the best chance for a definitive diagnosis and curative treatment.

References

1. Yoon YH, Kim JH, Kim KH, Baek WK, Lee HK, Lee MH, Lee KH, Kim L. Large cell neuroendocrine carcinoma of the thymus: a two-case report. Korean J Thorac Cardiovasc Surg. 2012 Feb;45(1):60-4.
2. Mega S, Oguri M, Kawasaki R, Hazama K, Iwai K, Kondo S. Large-cell neuroendocrine carcinoma in the thymus. Gen Thorac Cardiovasc Surg. 2008 Nov;56(11):566-9.
3. Ogawa F, Iyoda A, Amano H, Nezu K, Jiang SX, Okayasu I, Satoh Y. Thymic large cell neuroendocrine carcinoma: report of a resected case - a case report. J Cardiothorac Surg. 2010 Nov 22;5:115

Keywords

Mediastinum, Malignant tumor,