Lung Cancer |

Malignant Epithelioid Neoplasm Metastatic to the Lungs With an Unknown Primary Site FREE TO VIEW

Kevin Rowley, DO; William Frey, MD
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San Antonio Military Medical Center, Fort Sam Houston, TX

Chest. 2014;146(4_MeetingAbstracts):629A. doi:10.1378/chest.1993298
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SESSION TYPE: Affiliate Case Report Slide

PRESENTED ON: Wednesday, October 29, 2014 at 11:00 AM - 12:15 PM

INTRODUCTION: The lungs are a common site of distant metastasis for multiple malignancies. A metastatic process is high on the differential diagnosis in the setting of CT scan of the chest that shows multiple, bilateral, round nodules. However, identifying a primary malignancy can be clinically challenging.

CASE PRESENTATION: The patient is a 57 year old male who was identified with bilateral pulmonary nodules during CXR imaging for an upper respiratory infection. Chest CT showed multiple, round, bilateral nodules, the largest measuring 11mm in diameter with no associated adenopathy. He was referred to Pulmonary the following month with resolution of URI symptoms except for a mild, non-productive cough. The patient had no underlying risk factors for cancer and review of systems was negative. Physical examination was unremarkable. Additional CT imaging showed no likely source of primary malignancy and the nodules were not FDG avid on PET CT. A transthoracic needle biopsy was performed; pathology was suggestive of spindle cell thymoma. Surgical lung biopsy was performed to confirm the diagnosis with four parenchymal nodules resected. Morphology was suggestive of metastatic thymoma or myoepithelial neoplasm but IHC staining was not supportive of this diagnosis. FISH studies were negative for EWS and FUS gene rearrangements, effectively eliminating a myoepithelial neoplasm. The pathology specimens underwent expert analysis and were characterized as “malignant epithelioid neoplasm not further classified, probably metastatic.” The patient remains asymptomatic while undergoing surveillance chest imaging and no primary source of lung metastases has been identified.

DISCUSSION: This patient presents a diagnostic challenge as his presentation is indicative of a metastatic neoplastic process but nodule classification and identification of an extra-pulmonary source remain elusive. Given his clinically silent course, the current strategy of surveillance is sufficient and therapy may be delayed. The inability to ascertain a pathologic origin potentially complicates future decisions regarding his therapy.

CONCLUSIONS: This case represents a clinically silent, likely metastatic pulmonary neoplasm with an unknown source and unusual histologic features. This presentation makes characterization and management particularly challenging.

Reference #1: Lauren Xu and Allen Burke. Pulmonary Oligometastases: Histological Features and Difficulties in Dertermining Site of Origin. International Journal of Surgical Pathology. 2012 Dec; 20(6):577-588

DISCLOSURE: The following authors have nothing to disclose: Kevin Rowley, William Frey

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