| Session: Extramedullary manifestation of neoplastic myeloid disorder |
| Case number: 135 |
Submitter(s): Xiuyan Xie.
Clinical history
54 year old previously healthy woman presented in May 2006 for severe back pain. MRI of the lumbar spine showed multiple focal bony lesions suspicious for a neplastic process. The differential diagnosis was metastatic carcinoma or lymphoma. WBC 11.2, Hemoglobin 12.2, platelet 298. Biopsy of the L3 bon lesion (Biospy #1) was performed at the outside hospital. At the time, it was classified as atypical myeloid infiltrate, differential diagnosis included acute leukemia and myeloproliferative process. A bilateral bone marrow biopsies were performed. Due to extremely low level and focal involvement by APL, a diagnosis of APL was not made at the time. It was elected to follow the patient closely clinically. At the meantime, BCR-ABL and JAK2 V617F were done and they were negative. In November 2006, the patient presented with WBC 0.73, Hemoglobin 11.3, MCV 89.6, RDW 13.1; Platelet 122. Differential: Segs 41, Lymphs 48, Monos 11, Eos0, Basos 0. A bone marrow biopsy was repeated (Biopsy #2).
Details of gross/microscopic pathology:
Biopsy #1: Multiple fragments of bone and soft tisse were submitted entirely for decalcification. Section showed the soft tissue was almost entirely infiltrated by neoplastic cells. The neoplastic cells were large in size with finely dispersed chromatin, irregular nuclear contour, and clear to eosinophilic cytoplasm.[figure1]Biopsy #2: Bone marrow aspirate: 40% Blasts including promyelocytes. The promyelocytes have the morphology of microgranular variant of APL with deeply invaginated, some of them have ""dumbbell-shaped"" nuclear contour, prominent nucleoli, and numerous small azurophilic granules. Occasional Auer rods are seen, but ""Faggot cells"" were not identified.[figure2]
Immunophenotype (flow cytometry/immunohistochemistry):
Biopsy #1: Myeloperoxidase stain showed the neoplastic cells were diffusely and intensely positive.
Biopsy #2: Flow cytometry: The blasts express CD13, CD33, CD117, CD65, and dim CD19. A subpopulation of the blasts expresses CD34 and CD2.[figure3]
Cytogenetics:
Biopsy #2 Bone marrow: 46, XX, t(15;17) [7]/46, XX [13].
Molecular analysis:
Bioipsy #2: FISH: t(15;17) and RAR[alpha] gene.[figure4]
Interesting feature(s) of submitted case:
Initial presentation of acute promyelocytic leukemia at an extramedullary site is extremely rare with only few cases have been reported in the literature. Majority of extramedullary presentation of APL reported in the literature are patients with relapse APL. Because of its rarity, the diagnosis could sometimes be missed. This case illustrates the rare initial presentation of granulocytic sarcoma, manifestating clinically as acute promyelocytic leukemia 6 months later. The case demonstrates the challenge of making a diagnosis of APL in an extramedullary site, especially in bone tissue with lack of cytomorphologic evaluation and tissue processing that is suboptimal for molecular studies such FISH study for t(15;17).
Proposed diagnosis:
Biopsy #1: Granulocytic sarcoma, acute promyelocytic leukemia.
Biopsy #2: Acute promyelocytic leukemia (AML with t(15;17)(q22;q12)).
Panel diagnosis:
agree with proposed diagnoses
Comments:
Stains performed by the panel: MPO +, CD15+, NPM not evaluable
Images:
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