Primary muscle lymphoma in an elderly patient: Ultrasound and magnetic resonance imaging findings

Muscle lymphoma is a rarely seen disorder and it constitutes 0.1% to 1.4% of all extranodal lymphomas. It may be seen as the intramuscular involvement of disseminated disease, as an extension from adjacent bone or lymph nodes or as primary extranodal lymphoma. An 83-year-old female patient presented with the complaint of pain and swelling at her right calf. Ultrasound (US) examination of the region demonstrated a hypoechoic appearance of the affected muscle and subcutaneous tissue. Magnetic resonance imaging of the right calf demonstrated the long segmental involvement of the flexor digitorumlongus muscle and the adjacent subcutaneous tissue with the increased T2 signal, vivid enhancement, and diffusion restriction. US-guided core needle biopsy of the muscle was performed and histopathological evaluation demonstrated a B cell lymphoma. Further imaging workup with computed tomography for staging purpose revealed no other organ/system or nodal involvement. The patient was diagnosed with primary muscle lymphoma and received chemotherapeutic drugs.