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BACKGROUND Fluid overload-associated large B-cell lymphoma (FO-LBCL) is a recently described malignant lymphoma that presents with serous effusions in the pleura, peritoneum, and/or pericardium but without an identifiable lymphoma mass. This report describes the case of an 80-year-old man who presented with a pleural effusion and describes the approach to diagnosis and management of FO-LBCL. CASE REPORT We present a case of an 80-year-old man who presented with right pleural effusion and shortness of breath at work. Initial radiological assessment suggested a pleural effusion on the right side, without an identifiable mass, given the patient's symptoms and imaging characteristics. Subsequently, he underwent a pleural fluid puncture and biopsy. Based on the initial pathological assessment, malignant lymphoma, a non-epithelial tumor, was considered likely, but differentiation from reactive proliferative cells was difficult, given the patient's symptoms and cytologic characteristics. Postoperatively, histopathological examination and immunohistochemistry confirmed a diagnosis of FO-LBCL. After 1 year of follow-up, the condition had progressed and the patient died due to recurrence. CONCLUSIONS This report has presented a case of FO-LBCL in an elderly man with pleural effusion and described how this rare and recently described lymphoma was diagnosed and managed.

Metaplastic breast carcinoma (MBC) is very rare among all invasive breast carcinomas, accounting for less than 1.0% of them. MBCs are classified into five subtypes, including mixed MBC - where the mix might be multiple metaplastic elements or a mixture of epithelial and mesenchymal elements. Overall survival for mixed MBC tends to correlate with a significantly worse outcome. Therefore, an early accurate diagnosis and surgical treatment for mixed MBCs must allow for an improved quality of life and better prognosis. However, there have not been many recently published papers describing the detailed cytological features of mixed MBCs on fine-needle aspiration (FNA) specimens. A 60-year-old female presented with a history of a hard breast mass on the left lateral side, showing an ill-defined and marginally enhanced tumor nodule on magnetic resonance imaging. The cytologic specimens of FNA contained a large number of three-dimensional, cohesive and sheet-like clusters, or non-cohesive single cells, of highly atypical spindled sarcomatoid to oval epithelioid cells having hyperchromatic pleomorphic nuclei and mitotic figures, in a necrotic and hemorrhagic background. A small amount of osteoid matrix-like substance was rarely seen, associated with a very small number of osteoclast-like giant cells. We first interpreted it as an invasive breast carcinoma of high grade. A mastectomy was performed, and a gross examination of the neoplasm revealed a hemorrhagic solid tumor lesion with a gray-whitish cut surface, measuring approximately 35 × 24 × 21 mm in diameter. On a microscopic examination, the tumor was predominantly composed of the proliferation of highly atypical oval to spindled cells predominantly in a sarcomatous growth fashion with focal production of chondroid and osteoid matrix, peripherally coexisted with a smaller volume of conventional invasive breast carcinoma. Immunohistochemistry showed that the sarcomatous tumor cells were specifically positive for vimentin, α-smooth muscle actin, or epithelial membrane antigen. Therefore, we finally made a diagnosis of invasive mixed MBC with heterologous mesenchymal differentiation and conventional adenocarcinomatous elements. To the best of our knowledge, this would most recently be the first case report of mixed MBC with heterologous mesenchymal differentiation and conventional adenocarcinomatous elements, with a focus on its FNA cytomorphologic findings. We should be aware that owing to its characteristic cytological features, cytopathologists might be able to make a correct diagnosis of MBC, based on multiple and adequate samplings., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2024, Okanemasa et al.)