Track: Case Reports

Topic: Lymphoproliferative Disorders

Abstract:

Myeloid sarcoma (MS) is an uncommon extramedullary manifestation of acute myeloid leukemia (AML). We describe the case of a 78-year-old woman who presented to dermatology clinic with an exophytic forehead lesion. Histologic sections demonstrated a perivascular and syncytial dermal infiltrate of small to intermediate-sized cells with indented vesicular nuclei and scant cytoplasm with abundant associated hemorrhage. The lesional cells showed immunohistochemical expression of CD31 and ERG, concerning for cutaneous angiosarcoma. However, additional stains revealed expression of MPO, c-myc, CD4, and CD43; CD34 and CD117 were negative. A diagnosis of cutaneous myeloid sarcoma was rendered. Pathogenic ASXL1 p.G646fs and RUNX1 p.T246fs mutations, which are common in myeloid neoplasms, were detected on next-generation sequencing of the skin biopsy. The patient’s CBC showed normocytic, hypochromic anemia and thrombocytopenia with an absolute monocytosis. Bone marrow aspirate and biopsy revealed trilineage dysplasia and 38% blasts, including immature monocytes, confirming AML. A PET scan showed hypermetabolic activity in the marrow, spleen, scalp, bilateral calves, lymph nodes, and focally in the sigmoid/descending colon. The patient is status post five cycles of decitabine and venetoclax with the most recent bone marrow showing 5% blasts and repeat PET showing partial response of extramedullary disease. This report delineates a case of ERG-positive myeloid sarcoma exhibing clinical and histological similarities to cutaneous angiosarcoma, raising awareness of an important pitfall and emphasizing the utility of correlating with the patient’s CBC, imaging, and potentially molecular testing and bone marrow biopsy. Such an approach is indispensable for accurate classification and optimal therapeutic management.

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Shanelle De Lancy, MD