Acute Myeloid Leukemia Masquerading as Acute Appendicitis.

To the Editor: Extra medullary infiltration is often seen in acute myeloid leukemia (AML). Many take the form of tumor masses as myeloid sarcoma. However, leukemic cell infiltration of the appendix is rare. Herein, we report a case of AML initially presented as acute nonsuppurative appendicitis due to leukemic cell infiltration which is a rarer manifestation of de novo AML.

A 28-year-old Tibetan male referred to Department of Hematology, West China Hospital due to a sudden abdominal pain at the right lower quadrant. Before that, he had experienced a 3-month history of progressive epigastric pain which radiated to the back and was firstly diagnosed as acute pancreatitis in a local hospital. On admission, physical examination showed right lower quadrant tenderness at Mcburney's point with muscle rigidness and rebound tenderness. The complete blood count test showed a white blood cell (WBC) count of 23.27 × 109/L with neutrophilic predominance of 93%, a hemoglobin level of 80 g/L, and a platelet count of 60 × 1012/L. No blasts were spotted by peripheral blood smear. An enhanced abdominal computed tomography scan showed a larger and highly distended appendix with intraluminal fluid and a thickened wall [Figure 1]. He was suspected to have acute appendicitis and thereafter open appendectomy was performed instantaneously. In surgery, his appendix was found enlarged with a mass growth with a diameter of 6 cm in its tail. Pathology study showed profuse atypical cell infiltration in appendiceal wall without signs of purulent inflammation. Immunohistochemistry confirmed that these atypical mononuclear cells had a myeloid origin with focal positivity by myeloperoxidase staining. Hence, acute leukemic appendicitis/myeloid sarcoma of the appendage was diagnosed. After the surgery, the patient developed a high fever and a fast increasing WBC count up to 64.54 × 109/L with blasts over 80%. A diagnosis of acute myelomonocytic leukemia was made by bone marrow smear. As this patient had leukemic infiltration of the appendix, we supposed that it was the same case with his “pancreatitis”. Although cytarabine of 25 mg injected subcutaneously twice daily was given to control his leukemia with adequate antibiotic therapy, the patient died of severe sepsis one month after the surgery.

Figure 1

Abdominal computed tomography scan showing a swollen appendix (arrow) with circularly enhanced walls (a). The appendix (arrow) is obviously enlarged (b).

Besides the commonly involved sites such as the skin, lymph node, soft tissue, and testis, infiltration of leukemic cells in the appendix is rare in AML. Limited cases have been reported.[1234] Most of the symptomatic cases happened in the course of leukemia relapse or progression.[23] Some were incidentally revealed by postmortem study.[5] Although patients in the known setting of AML who develop abdominal pain after receiving chemotherapy are often found to have suppurative appendicitis after surgical intervention, acute leukemic appendicitis as the initial manifestation of AML proven on pathological review is even rarer,[34] and early recognition is difficult, especially when there is no obvious blasts in the peripheral blood like our case.

In general, systemic chemotherapy even in combination of radiotherapy is needed for myeloid sarcoma after surgery. However, myeloid sarcoma is associated with a poor prognosis in the long run. Although surgical intervention is the standard management for acute appendicitis whether it is leukemic or suppurative, for AML patients, appendectomy is indicative of high operative morbidity and subsequent life-threatening infection even with successful previous cases.[23] Our patient was successfully operated and was given cyto-reductive chemotherapy in time. However, just like the above-mentioned concern, he did not survive the postoperative sepsis due to continuous immuno-impairment status of AML. Nevertheless, this case has reminded us that acute leukemia should not be neglected in the setting of a significant leukemoid reaction even if an obvious acute process like appendicitis is present.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.