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Case of the Month

A 59-year-old man presented with left upper quadrant discomfort and was found to have hepatosplenomegaly. Complete blood count (CBC) showed WBC of 19.0 K/μL. Red blood cell indices and platelets were within normal limits. The peripheral blood differential showed 72 percent lymphocytes, 23 percent neutrophils, and 4 percent monocytes (see Figure 1A).  A bone marrow biopsy demonstrated diffuse interstitial involvement by small lymphoid cells, comprising approximately 30 percent of bone marrow cellularity. TCL-1 immunohistochemical stain was performed on the bone marrow core (Figure 1B). Flow cytometric analysis (Figure 2A) and FISH study for TRA/D locus (Figure 2B) are shown.

Which is the most likely diagnosis?

a. T-cell large granular lymphocytic leukemia 
b. Adult T-cell leukemia/lymphoma 
c. Sezary syndrome
d. T-cell prolymphocytic leukemia
e. Peripheral T-cell lymphoma, NOS

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We will reveal the answer next month.

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The Case of the Month series is curated by Anamarija M. Perry, University of Michigan.

C. Mycobacterial infection

Sections demonstrate hypercellular bone marrow, with sheets of large histiocytes (Image 1) whose cytoplasm appears to have a “crinkled tissue paper” quality (Image 2). A Ziehl-Neelsen stain highlighted numerous intracellular acid-fast bacilli (Image 3). Bone marrow aspirate cultures were positive for Mycobacterium avium.

M. avium complex (MAC) is composed of several species, including M. avium and M. intracellulare. Both organisms are acquired from the environment via inhalation or ingestion and stain positive with acid-fast preparations. Those with competent immune systems may develop an isolated pulmonary disease. However, immunocompromised or immunosuppressed patients, such as those with AIDS or post-chemotherapy, often develop disseminated disease (1). Follow-up genetic testing revealed a primary immunodeficiency syndrome in this patient.

Morphologic findings in the bone marrow, coupled with the patient’s splenomegaly, raise the differential diagnosis of lysosomal storage disorders, including Gaucher and Niemann-Pick diseases. Both diseases are due to autosomal recessive mutations which lead to enzymatic deficiencies – ß-glucocerebrosidase and acid sphingomyelinase, respectively – that result in the accumulation of sphingolipids within “storage macrophages” in the spleen, liver, lymph nodes, and bone marrow. These patients experience a constellation of signs and symptoms (depending on the disease subtype) and genetic testing is needed to confirm the diagnosis (2). Pseudo-Gaucher cells are a consequence of rapid cell turnover and are usually seen in myeloproliferative neoplasms; unlike true Gaucher cells, they do not stain positively for iron (3). Crystal-storing histiocytosis (CSH) is a rare condition in which intralysosomal accumulation of immunoglobulins causes crystal formation within histiocytes. CSH may involve lymph nodes, spleen, liver, bone marrow, as well as other extranodal sites. Patients with CSH usually have an underlying B-cell lymphoma or plasma cell neoplasm. Crystals will usually stain positive for monotypic kappa or lambda light chain (4).

Submitted by Anna B. Owczarczyk, University of Michigan, Ann Arbor, Michigan, USA.

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  1. PR Murray et al., “Mycobacterium and related acid-fast bacteria”, Medical Microbiology, 8th edition, 226. Elsevier: 2016.
  2. CR Ferreira, WA Gahl, “Lysosomal storage diseases”, Transl Sci Rare Dis, 2, 1 (2017). PMID: 29152458.
  3. DP O’Malley et al., “Non-neoplastic morphologic abnormalities of white blood cells and macrophages”, Hematopathology, 3rd edition, 106. Elsevier: 2017.
  4. R Kanagal-Shamanna et al., “Crystal-storing histiocytosis: a clinicopathological study of 13 cases”, Histopathology, 68, 482 (2016). PMID: 26118455.
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