Myeloid sarcoma with RBM15::MRTFA (MKL1) mimicking vascular neoplasm

Extramedullary involvement of acute myeloid leukemia (AML), aka myeloid sarcoma, is a rare phenomenon in acute megakaryoblastic leukemia with RBM15:: MRTFA(MKL1) fusion, which might mimic non-hematologic malignancies. A 7-month-old infant presented with leukocytosis, hepatosplenomegaly, multiple lymphadenopathies, and a solid mass in the right thigh. Initially, the patient was diagnosed with a malignant vascular tumor regarding the expression of vascular markers from the biopsy of the right thigh lesion that was performed after the inconclusive bone marrow biopsy. The second bone marrow biopsy, which was performed due to the partial response to sarcoma treatment, showed hypercellular bone marrow with CD34 and CD61-positive spindle cell infiltration and > 20% basophilic blasts with cytoplasmic blebs. RNA sequencing of soft tissue biopsy revealed the presence of RBM15::MRTFA(MKL1) fusion. Based on these findings, myeloid sarcoma/AML with RBM15::MRTFA(MKL1) fusion diagnosis was made. AML with RBM15::MRTFA(MKL1) fusion can initially present as extramedullary lesions and might cause misdiagnosis of non-hematologic malignancies.

Primary monophasic synovial sarcoma of the lung: Rare case report

Primary monophasic synovial sarcoma of the lung is an extremely rare malignant mesenchymal tumor that can develop at any anatomic site. Synovial sarcoma is considered a high grade tumor with a poor prognosis. Metastatic pulmonary sarcoma is much more common. Hence primary lesion elsewhere in the body needs exclusion. No clinical or radiological features are specific for pulmonary sarcoma, often it is confused with bronchogenic carcinoma. Therefore biopsy is needed to establish the diagnosis of this rare tumor. We hereby present two cases of histologically proven primary monophasic synovial sarcoma of lung. The imaging features of this rare disease is reviewed.

A Rare Case of Primary Malignant Mesenchymoma Arising from Submandibular Salivary Gland

Malignant mesenchymoma is a rare tumor in which there are two or more distinct mesenchymal components. These are generally considered as high-grade neoplasms and are usually associated with a poor prognosis. Here, we report a case of malignant mesenchymoma containing undifferentiated spindle cell sarcoma, leiomyosarcoma, chondrosarcoma, osteosarcoma, and areas with rhabdoid differentiation in a 54-year-old male. The primary tumor measured 5.5 × 4 × 3 cm and weighed 135 g arising from the left submandibular salivary gland. Fine-needle aspiration cytology showed the presence of pleomorphic spindle cell clusters with atypia and myxoid stroma. An impression of malignant salivary gland neoplasm was given. Diagnosis of malignant mesenchymoma was made on histopathological examination supported by immunohistochemistry showing strong positivity with p53, Ki-67, and focal positivity for smooth muscle actin, S-100, desmin, and negativity for cytokeratins. The exact histogenesis of malignant mesenchymoma and the optimal management strategy to decide the prognosis remains uncertain as it is a rare tumor.