A case of anaplastic large cell lymphoma of skeletal muscle

Anaplastic large cell lymphoma (ALCL) is a high grade non‐Hodgkin lymphoma (NHL) that is comprised of the malignant proliferation of large lymphoid cells, which express CD30. Primary ALCL of the skeletal muscle is extremely uncommon. A 51‐year‐old Japanese female presented at our hospital with a 2‐month history of severe pain and swelling of the right leg. A gallium‐67 SPECT/CT scan showed a large mass involving the skeletal muscles from the gluteus to femoris. A biopsy of the mass demonstrated diffuse infiltration of medium and large neoplastic cells with round or lobulated hyperchromatic pleomorphic nuclei. A subset of Reed‐Sternberg‐like cells was also identified. Immunohistochemically, the neoplastic cells were strongly positive for CD4 and CD30, but negative for CD3, CD8, anaplastic lymphoma kinase (ALK), CD20, CD79α, CD21 and CD23. Based on the histological examination, this patient was diagnosed to have ALK‐negative ALCL of the skeletal muscle. Further studies are needed to clarify the biological behavior of primary skeletal muscle ALCL.