Micronodular Thymoma with Lymphoid Stroma: A Mediastinal Mass Masquerading as a Pericardial Mass.

A 61-year-old man presented to the emergency room with lower extremity edema. Physical exam was only remarkable for a diastolic murmur in the right carotid area and left lower extremity edema. Venous Doppler revealed a deep venous thrombosis in the left lower extremity. Chest computed tomography (CT) with intravenous contrast ruled out pulmonary embolism but showed a mediastinal mass adjacent to the pericardium. Further imaging with cardiac magnetic resonance imaging (CMR) and cardiac CT angiography (CCTA) enabled localization and evaluation of the structural characteristics of the mass. The decision was made to excise the mass due to increasing size compared with its measurements on prior chest CTs and a high degree of vascularization seen on CMR and CCTA, which was concerning for an enlarging arteriovenous malformation or a hemangioma. However, histopathologic analysis of the mass revealed it to be a micronodular thymoma.

Lobular to Lobule: Metastatic Breast Carcinoma to Olfactory Neuroblastoma.

Tumor-to-tumor metastasis (TTM) is a rare, but well-described phenomenon occurring in patients with multiple synchronous or metachronous primary malignancies. Olfactory neuroblastoma (ONB) is a rare malignant, neuroectodermal sinonasal tract tumor that occurs within the ethmoid sinus involving the cribriform plate. Very few cases of ONB have been documented to metastasize to other primary malignancies, but the reverse scenario is exceptional. During an evaluation for anosmia, a right nasal polyp was identified on imaging and endoscopy in a 66-year-old woman, with a polypectomy performed. Histologic examination showed classical features of a low-grade olfactory neuroblastoma, but within the tumor were isolated epithelioid cells which were strongly pancytokeratin immunoreactive. Review of the clinical history revealed lobular breast carcinoma treated 10 years earlier. Further evaluation with immunohistochemistry showed strong and diffuse nuclear estrogen and progesterone receptor reactivity, along with GATA3. These results confirmed TTM of an invasive lobular breast carcinoma to ONB. By employing a limited immunohistochemistry panel for all small round blue cell tumors that includes pancytokeratin, p40, S100 protein, SOX10, synaptophysin, desmin, CD99, and CD45, one is able to more accurately diagnose the classical tumor types, while also showing potentially unusual tumor features or exceptionally rare events like metastatic lobular breast carcinoma to ONB.