Cutaneous extranodal natural killer/T-cell lymphoma mimickin
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A 53-year-old Hispanic male presented with painful left lower extremity swelling and erythema. He had recently completed a course of cephalexin for left leg cellulitis, yet his symptoms worsened. Six months prior, enlarging bilateral adrenal and periaortic retroperitoneal masses were discovered incidentally on (MRI); however, the patient was lost to follow up preventing further work-up. On current presentation, he endorsed intermittent fevers, episodic night sweats, decreased appetite, and palpitations. He denied recent leg trauma or penetrating injury. Physical examination revealed ill-defined, warm, confluent erythema, edema, and tender induration of the left calf.

Laboratory tests showed mild lymphocytopenia, moderate anemia, elevated creatinine protein kinase, elevated aldolase, and elevated lactate dehydrogenase. CT and MRI of the leg revealed myositis of the gastrocnemius muscle, extensive subcutaneous and superficial myofascial edema, and popliteal lymphadenopathy without lymphatic obstruction. The patient was started on intravenous ceftriaxone for high suspicion of cellulitis and pyomyositis.

A punch biopsy of the skin from the lower leg showed a sparse perivascular and interstitial infiltrate of enlarged atypical mononuclear cells in the deep dermis and subcutis, not consistent with cellulitis. Given the findings of a gastrocnemius muscle biopsy flow cytometry performed just prior, which demonstrated 10% natural killer cells expressing CD2, CD3, CD7, CD56 as well as EBV, similar stains were performed on the skin.

A retroperitoneal mass core needle biopsy showed a similar population of neoplastic cells with a Ki-67 immunostain demonstrating high proliferative activity of 70-80%. There was no evidence of lymphoma cells on bone marrow biopsy. Polymerase chain reaction identified EBV DNA in the blood with a viral load of 600,000 copy/ml. Fiberoptic rhinoscopy did not show neoplasm of the nasopharynx. PET-CT identified hypermetabolic tissue centered around the left para-aortic space and bilateral adrenal masses; no nasal lesions were found.

Based on these findings, stage IV extranodal natural killer/T-cell lymphoma, nasal type, was diagnosed. The patient was started on six cycles of modified SMILE chemotherapy regimen (dexamethasone, ifosfamide, etoposide, and pegaspargase) with the ultimate plan of autologous hematopoietic stem cell transplantation.