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Chapter 36: Inflammatory and Malignant Histiocytosis

INTRODUCTION

  • The terms histiocyte and macrophage are synonyms for the mature cell of the monocyte-macrophage system. The latter is the preferred term in discussions of cell biology and immunology, but “histiocytosis” continues to be used by pathologists and in textbooks for diseases of macrophages because of its entrenchment in the medical literature.

  • A classification of the histiocytoses most relevant to hematologists is shown in Table 36–1. They have been classified based on whether they are monocyte-derived dendritic cell–related, monocyte-macrophage–related, or neoplastic transformations of dendritic cells or macrophages.

  • Distinctions among the diseases of macrophages are made based on clinical findings, histopathology, immunophenotyping of surface antigen, cytochemistry, and cytogenetic or genetic features (Table 36–2).

TABLE 36–1CLASSIFICATION OF HISTIOCYTIC DISORDERS
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TABLE 36–1 CLASSIFICATION OF HISTIOCYTIC DISORDERS

  1. Disorders of varying biologic behavior, lacking cytologic atypia

    1. Dendritic-cell-related

      1. Langerhans cell histiocytosis

      2. Juvenile xanthogranuloma

      3. Erdheim-Chester disease

    2. Monocyte-macrophage related

      1. Hemophagocytic lymphohistiocytosis: familial and/or with identified dysfunctional gene mutation

      2. Secondary hemophagocytic syndromes

        1. Infection-associated

        2. Malignancy-associated

        3. Autoimmune-associated

        4. Other

      3. Sinus histiocytosis with massive lymphadenopathy (Rosai-Dorfman disease)

      4. Solitary histiocytoma of macrophage phenotype

  2. Malignant disorders

    1. Dendritic cell related

    2. Histiocytic sarcoma

    3. Monocyte-macrophage related

    4. Leukemias: monocytic M5A and M5B, myelomonocytic M4, chronic myelomonocytic leukemia

Source: Williams Hematology, 9th ed, Chap. 71, Table 71–2.

TABLE 36–2DIFFERENTIATING CHARACTERISTICS OF HISTIOCYTES
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TABLE 36–2 DIFFERENTIATING CHARACTERISTICS OF HISTIOCYTES
Histologic Features LCH Malignant Histiocytosis ECD/JXG HLH RDD
HLH-DR ++ + – + +
CD1a ++ +/– – – –
CD14 – +/– ++ ++ ++
CD68 +/– +/– ++ ++ ++
CD163 – – + ++ ++
CD207 (Langerin) +++ +/– – – –
Factor XIIIa – – ++ – –
Fascin – +/– ++ +/– +
Birbeck granules + +/– – – –
Hemophagocytosis +/– – – +/– –
Emperipolesis – – – – +

CD, cluster of differentiation; ECD, Erdheim-Chester disease; HLH, hemophagocytic lymphohistiocytosis; JXG, juvenile xanthogranuloma; LCH, Langerhans cell histiocytosis; RDD, Rosai-Dorfman disease.

Source: Williams Hematology, 9th ed, Chap. 71, Table 71–1.

CLONAL HISTIOCYTOSES

Langerhans Cell Histiocytosis

Definition and History

  • The term Langerhans cell histiocytosis includes disorders previously called histiocytosis X (eosinophilic granuloma, Letterer-Siwe disease, Hand-Schüller-Christian disease), self-healing histiocytosis, and Langerhans cell granulomatosis.

  • Langerhans cells are macrophages with irregularly shaped nuclei present in epidermis, mucosa, lymph nodes, thymus, and spleen.

  • As all macrophages types, they originate in marrow from a multipotential hematopoietic cell.

  • Identified by unique racquet-shaped ultrastructural inclusions (Birbeck bodies) and by immunoreactivity to neuroprotein S-100, neuronal specific enolase, and surface antigen CD1a and CD207 (Langerin). Birbeck bodies, CD1a expression, and strong CD207 expression are pathognomonic for Langerhans cells.

  • The principal function of Langerhans cells is to process antigen and present it to T cells.

Etiology and Pathogenesis

  • Although long thought to ...

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