Primary Soft Tissue DLBCL Mimicking Sarcoma

A 64-year-old lady without any comorbidities presented with left lower limb swelling for 2 years, gradually increasing in size and associated with pain for 3 months. Examination of left leg revealed multifocal non-tender swellings along the anterior aspect, extending from the ankle to the tibial tuberosity. The swellings were hard, fixed to the underlying bone and muscle. There was no hepatosplenomegaly or palpable lymph nodes elsewhere. Magnetic resonance imaging identified heterogeneous mass around the tibia, involving muscles and subcutaneous tissue, superiorly extending to popliteal fossa, encasing popliteal vessels. The patient underwent an ultrasound-guided biopsy which revealed diffuse large B-cell lymphoma (DLBCL), GCB subtype. The patient was managed on lines of extranodal NHL and planned for positron emission tomography followed by chemotherapy and consolidative radiotherapy. This is a rare case of soft tissue DLBCL, clinically and radiologically masquerading as a soft tissue sarcoma. In cases of atypical soft tissue masses like multifocal swellings, especially without lymphadenopathy, a high index of suspicion for extranodal lymphoma should be maintained, and immunohistochemistry is essential following biopsy for definitive diagnosis and accurate management.