Connecting the Dots: A Case of Myeloid Sarcoma

A 73-year-old white gentleman with a medical history significant for stage IIA (pT3a, N0, M0) malignant melanoma managed by wide local excision from his right shoulder was referred to our cutaneous clinic for evaluation of locally recurrent disease. An excisional biopsy of the lesion 3 months prior had been interpreted as consistent with malignant melanoma, spindle cell type, with an invasive component and positive margins. Immunohistochemical staining was negative for pankeratin, desmin, HMB 45, and Melan A, yet positive for S100, supporting the assigned diagnosis. Positron emission tomography/computed tomography imaging ordered for staging reported no evidence of focal hypermetabolic activity but did note splenomegaly and diffuse enhancement throughout the skeletal system consistent with marrow stimulation. During his follow-up appointment to review the imaging, his examination revealed an interval appearance of multiple painless, nonpruritic erythematous nodules on the torso and arms. He denied any associated constitutional symptoms (eg, fevers, night sweats, unintended weight loss, excessive fatigue). Three years prior to presentation, he had undergone an extensive workup for thrombocytopenia and leukocytosis. This included a bone marrow biopsy that was negative for malignancy or myelodysplastic syndrome. The patient was otherwise healthy and active.