Acute monocytic leukemia presenting as generalized lymphadenopathy and skin rash in a toddler: highlighting the clinicopathologic mimics

Abstract

Acute myeloid leukemia (AML) is the fifth most common malignancy in children. Extramedullary involvement in acute myeloid leukemia is rare and can be seen in soft tissues, central nervous system, skin and lymphoreticular organs. The clinical presentations can often be non‐specific and hence, the diagnosis can be very challenging, especially in cases without a prior hematologic diagnosis. We report a case of pediatric acute monocytic leukemia presenting with generalized lymphadenopathy and cutaneous rash. Fine‐needle aspiration was performed from the lymph nodes and a cytologic diagnosis of infiltration by a lymphoreticular malignancy was suggested. Peripheral blood, bone marrow and cerebrospinal fluid involvement were noted subsequently. Flow cytometry on the bone marrow aspirate confirmed a diagnosis of acute monocytic leukemia. The index case besides highlighting an uncommon presentation of acute monocytic leukemia in a toddler, also emphasizes the need to consider acute monocytic leukemia as a cytomorphologic differential in such presentations.

Acute monoblastic myeloid leukemic pleural effusion: Pitfalls and clues

“…Most are secondary manifestations of an existing disease, while primary presentations are unusual 2,4–7,9 . Clinically and cytologically, the differential diagnosis is broad 2,6–8 . Our case showed myeloid leukemic infiltrate of monocyte lineage that morphologically simulated different cell types.…”

“…2,[4][5][6][7]9 Clinically and cytologically, the differential diagnosis is broad. 2,[6][7][8] Our case showed myeloid leukemic infiltrate of monocyte lineage that morphologically simulated different cell types. Initially, the infiltrate was morphologically confused with florid reactive mesothelial cells or chronic histiocyte-rich inflammatory effusion.…”

“…The reported incidence of acute myeloid leukemic serous effusions ranged between 0.1% and 0.4%, however the true incidence may be underestimated 1,4,6 . Pleural effusions due to acute myeloid leukemia of monocyte origin are rarer 7,8 . Most are secondary manifestations of an existing disease, while primary presentations are unusual 2,4–7,9 .…”

“…1,4,6 Pleural effusions due to acute myeloid leukemia of monocyte origin are rarer. 7,8 Most are secondary manifestations of an existing disease, while primary presentations are unusual. 2,[4][5][6][7]9 Clinically and cytologically, the differential diagnosis is broad.…”

“…This is further compounded because some monoblastic and to lesser extent monocyte leukemias often lack expression of other myeloid immunomarkers such as CD10, CD117 and CD34. [1][2][3][4][5][6][7][8][9] Another consideration to explain the unusual findings in the pleural fluid is the cells are more differentiated and more suggestive of histiocytic sarcoma. Even though histiocytic sarcoma has overlapping immunophenotypic features, peripheral blood and bone marrow are usually not involved in histiocytic sarcoma contrary to acute monocytic leukemia.…”