MALT lymphoma of the left biceps muscle: a rare case with an interesting presentation

BACKGROUND: Extranodal marginal zone lymphoma (MZL), also called mucosa-associated lymphoid tissue (MALT) lymphoma accounts for 7–8 % of non-Hodgkin lymphomas (NHLs) and most commonly involves the stomach. However, muscle involvement is very rare. CASE DESCRIPTION: A 57-year-old woman was referred to our orthopaedics and traumatology clinic with a painful lump in the left arm. Physical examination revealed a red-colored mass on the left arm and an enlarged lymph node measuring almost 5 cm in the left axillary region and 3 cm in the right axillary region. Tru-cut biopsy of the mass in the left arm was consistent with MZL. The diagnosis was MALT lymphoma infiltrating the skeletal muscle (stage IIEA). R-CHOP was started. Two additional infusions of rituximab were administered after the sixth cycle of R-CHOP. Then, the patient received radiotherapy to the left arm at a dose of 30 Gy. After 1 year of follow-up, the patient had no evidence of disease. DISCUSSION AND EVALUATION: MALT lymphoma arises in a number of epithelial tissues. The clinical presentation of MALT lymphoma varies depending upon the tissue involved. To our knowledge, rare cases of MALT lymphoma of the skeletal muscle have been reported. Although the available literature suggests that primary skeletal muscle NHL with advanced stage is associated with poor prognosis, the case presented here suggests that rituximab based combination therapy followed by radiotherapy can be an effective treatment for primary skeletal MALT lymphoma. CONCLUSION: There is limited data regarding the prognosis and treatment of MALT lymphoma of the skeletal muscle. This case implies that rituximab based combination therapy followed by radiotherapy should be considered for the treatment of primary skeletal MALT lymphoma.