Fig. 3.1
Reactive lymphadenopathy (Diff-Quik stain, medium power). This case of reactive lymphadenopathy shows a follicle-like organization, in which the lymphoid cells cluster together with tingible body macrophages. The lymphoid population appears polymorphous, which is helpful in excluding a lymphoid malignancy.
Fig. 3.2
Reactive lymphoid hyperplasia with artifact (a–c. Diff-Quik stain, medium power; d. Diff-Quik stain, low power). Some cases of reactive lymphoid hyperplasia have artifactual changes such as air-drying artifact (a, b) and crush artifact (c), that can make the cells appear, paler (a), blown up (b) or spindled (c), and may raise concern for a metastatic neoplasm or lymphoproliferative disorder. In addition, when smears are too thick, the cytological features and lymphoglandular bodies may be difficult to identify (d).
3.2.3 High Power Microscopic Examination
The presence of lymphoglandular bodies is an important diagnostic feature of benign and malignant lymphoid populations (Fig. 3.1). When lymphoglandular bodies are present supporting a lymphoid proliferation, the next step is to assess the homogeneity or heterogeneity of the constituent cells, the size(s) of the cells, and the presence or absence of tingible body macrophages. The size of lymphoid cells is usually described in relation to a histiocyte nucleus or 2–3 red blood cells, with small, intermediate and large lymphoid cells being smaller than, the same size as, and larger than the nucleus of a histiocyte, respectively. The size of the predominant population helps to narrow the differential diagnosis. Features suggestive of malignancy include a homogeneous lymphoid population, predominance of large cells, marked pleomorphism, and/or an absence of tingible body macrophages, and should prompt collection of additional material for flow cytometry, cell block, and/or fluorescence in situ hybridization (FISH). In the setting of clinical findings suggestive of lymphoma, such as extensive lymphadenopathy or an elevated LDH, the presence of numerous mitotic figures and tingible body macrophages should also lead one to consider a high-grade lymphoma, such as Burkitt lymphoma. In contrast, features of reactive lymphoid proliferations include a heterogeneous population of cells with a predominance of small mature lymphocytes, lymphohistiocytic aggregates, and scattered tingible body macrophages (Fig. 3.1). Other features that provide important clues to the differential diagnosis include the presence or absence of other hematolymphoid cells (including eosinophils, neutrophils, plasma cells and histiocytes), granulomas , necrosis, and non-hematolymphoid cells.
Differential Diagnosis
Causes of lymphadenopathy in children and adolescents are summarized in Table 3.1, which categorizes the entities based on whether they are benign or malignant and common or uncommon (Figs. 3.3, 3.4, and 3.5). Differential diagnostic considerations based on eight morphologic patterns are listed in Table 3.2 and those based on the size of the predominant population are listed in Table 3.3. Primary lymphoid malignancies must be distinguished from metastatic small round cell tumors, which are summarized in Table 3.4.
Table 3.1
Summary of benign and malignant causes of lymphadenopathy in children and adolescents
Benign | Common | • Reactive lymphoid hyperplasia • Acute suppurative and/or granulomatous lymphadenitis • Infection, including Epstein–Barr virus, Bartonella (cat scratch disease), atypical mycobacteria, and M. tuberculosis |
Uncommon | • Sinus histiocytosis with massive lymphadenopathy (Rosai-Dorfman Disease) • Dermatopathic lymphadenitis • Histiocytic necrotizing lymphadenitis (Kikuchi disease) • HIV-associated lymphadenopathy • Drugs (e.g., Dilantin, methotrexate) • Vaccines • Foreign body/iatrogenic • Metabolic/storage disorders • Autoimmune disease, including systemic lupus erythematosus, rheumatoid arthritis, autoimmune lymphoproliferative syndrome • Chronic granulomatous disease • Nodal extramedullary hematopoiesis • Fungal or parasitic infection | |
Malignant | Common | • Acute lymphoblastic leukemia/lymphoma • Hodgkin lymphoma • Non-Hodgkin lymphomas, including diffuse large B- cell lymphoma, Burkitt lymphoma, and T-cell lymphomas |
Uncommon | • Small B-cell non-Hodgkin lymphoma • Metastatic malignancies |
Fig. 3.3
Composite of benign causes of pediatric lymphadenopathy.
Fig. 3.4
Composite of malignant causes of pediatric lymphadenopathy.
Fig. 3.5
Composite of uncommon causes of pediatric lymphadenopathy.
Table 3.2
Diagnostic patterns in pediatric lymph node cytopathology
Pattern 1: Heterogeneous lymphoid population with clean background • Reactive lymphoid hyperplasia • Drugs • Vaccines • Autoimmune disease • Progressive transformation of germinal centers • Infection (early stages of infection or chronic infection) • Nodal extramedullary hematopoiesis • Neoplasms (e.g., classical Hodgkin lymphoma with paucity of Reed–Sternberg cells, post-transplant lymphoproliferative disorder, T-cell lymphoma) |
Pattern 2: Heterogeneous lymphoid population with numerous histiocytes or granulomas • Infection (e.g., mycobacteria, fungi, toxoplasmosis) • Sinus histiocytosis with massive lymphadenopathy (Rosai-Dorfman Disease) • Langerhans cell histiocytosis • Foreign body or iatrogenic related lymphadenopathy • Hemophagocytosis and hemophagocytic lymphocytosis (hemophagocytic syndrome) • Metabolic or storage diseases • Chronic granulomatous disease • Sarcoid |
Pattern 3: Heterogeneous lymphoid population with increased plasma cells • Castleman disease • Autoimmune diseases • IgG4 related lymphadenopathy • Infection (e.g., toxoplasmosis) • Neoplastic entities (e.g., plasmablastic or plasmacytoid lymphoma) |
Pattern 4: Heterogeneous lymphoid population with increased eosinophils • Kimura disease • Langerhans cell histiocytosis • Hypereosinophilia syndrome • Drugs • Infection (e.g., parasites) • Neoplastic entities (e.g., Classical Hodgkin lymphoma, T-cell lymphoma) |
Pattern 5: Heterogeneous lymphoid population and intracellular or extracellular pigment • Dermatopathic lymphadenitis • Tattoo • Nodal nevi • Metastatic malignant melanoma • Contamination (e.g., lead from pencil, metallic pigment from stylet for needles) |
Pattern 6: Heterogeneous lymphoid population with dirty/necrotic background • Acute suppurative lymphadenitis • Infection (e.g., cat scratch disease, mycobacteria, pneumocystis, herpes simplex virus) • Histiocytic necrotizing lymphadenitis (Kikuchi-Fujimoto disease or Kikuchi disease) • Autoimmune disease (Systemic lupus erythematosus related lymphadenopathy) • Chronic granulomatous disease • Lymph node infarction• Drug or treatment-related changes • High-grade malignancy (hematolymphoid or metastasis) |
Pattern 7: Homogeneous population, small-to-intermediate cell predominant • Infectious mononucleosis • Acute lymphocytic or myeloid leukemia • Non-Hodgkin lymphoma (e.g., lymphoblastic or Burkitt lymphoma) • Metastatic small round cell malignancies |
Pattern 8: Homogeneous population, large cell predominant • Classical Hodgkin lymphoma with numerous Reed–Sternberg cells • Non-Hodgkin lymphoma (e.g., Burkitt lymphoma, diffuse large B-cell lymphoma, anaplastic large cell lymphoma) • Non-hematopoietic malignancy (e.g., metastatic sarcoma, germ cell tumor, or melanoma) |
Table 3.3
Size-based differential diagnosis for lymph node aspirates in children and adolescents
Small cell population Reactive lymphoid hyperplasia Early infection Hodgkin lymphoma with paucity of Reed–Sternberg cells Leukemia or myeloid/granulocytic sarcoma Small B-cell lymphoma (rare) T-cell lymphoma Non-lymphoid small round cell tumors | Intermediate cell population Reactive immunoblastic proliferations Infectious mononucleosis Lymphoblastic lymphoma Burkitt lymphoma T-cell lymphoma Leukemia or myeloid/granulocytic sarcoma Non-lymphoid small round cell tumors |
Monomorphic large cell population Diffuse large B-cell lymphoma Anaplastic large cell lymphoma Hodgkin lymphoma, with predominance of Reed–Sternberg cells) Germ cell tumors Sarcomas Malignant melanoma | Pleomorphic large cell population Diffuse large B-cell lymphoma (e.g., anaplastic) Anaplastic large cell lymphoma Germ cell tumors High-grade sarcomas Malignant melanoma |
Table 3.4
Differential diagnosis of small round cell tumors (adapted from Monaco SE and Teot LA. Cancer Cytopathol 2014) [8]
Cytomorphology | Immunophenotype | Genetics | |
|---|---|---|---|
Wilms’ Tumor | Blastema +/− epithelial component +/− stroma Rarely, anaplasia | + WT1 + EMA, Cytokeratin (epithelial component) − Synaptophysin, chromogranin | Mutations of WT1, WT2 |
Neuroblastoma | Neuropil, rosettes, +/− ganglion cells, +/− schwannian stroma, +/− calcification | + synaptophysin, chromogranin, CD56, PGP9.5 − S100, CD99, desmin, myogenin, lymphoid markers | +/− N-MYC amplification |
Rhabdomyosarcoma | Rhabdomyoblastic differentiation subtle to obvious +/− Floret cells, +/− strap cells | + Myogenin, myoD1, desmin − TLE1 +/− aberrant CD99, cytokeratin, EMA, neural markers | Alveolar subtype: t(2;13)(q35;14) t(1:13)(p36;q14) |
Ewing sarcoma/primitive neuroectodermal tumor (PNET) | +/− Rosettes, +/− neuropil +/− Tigroid background | +CD99, FLI-1 +/− Synaptophysin, PGP9.5, CD56 − Desmin, myogenin, CD45, TLE-1, EMA, cytokeratins | t(11;22)(q24;q12) (>90 %) t(21;22)(q12;q12), t(2;22)(q33;q12) Others (rare) |
Synovial sarcoma (poorly differentiated round cell) | +/− Metachromatic stroma, +/− calcifications | + TLE-1, +EMA, +/− cytokeratin, +/− CD99 − Myogenin, myoD1, desmin | t(X;18) (p11.2;q11) |
Lymphoid malignancies | Morphology varies with type Lymphoglandular bodies | Varies with lineage and type (B-cell, T-cell) +TdT (Lymphoblastic lymphoma) | Burkitt: MYC translocations, t(8;14)(q24;q32) and less commonly, t(2;8)(p12;q24), t(8;22)(q24;q11) |
Pearls
Avoid examination of areas on a slide with artifactual distortion, such as crush artifact or air-drying artifact, where the cells appear poorly preserved and/or pale (Fig. 3.2).
The key features to evaluate in lymph node aspirates from children and adolescents include: presence or absence of cohesion; the type of lymphoid population (heterogeneous versus homogeneous); the size(s) of the constituent cells ; the presence or absence of certain cell types (macrophages and/or granulomas, plasma cells, immunoblasts, eosinophils, neutrophils, and non-hematolymphoid cells ); and the background (clean versus necrotic).
3.3 Mimics of Lymphadenopathy
Some lesions, particularly superficial masses in the head and neck, mimic a lymph node clinically and/or radiologically due to their well-circumscribed nature and location, but prove to be other structures or processes on pathological examination. It is important to be aware of these entities and recognize their cytological features to ensure appropriate management. Pediatric head and neck lesions that can mimic lymphadenopathy are listed in Table 3.5 and selected lesions are illustrated in Fig. 3.6. Aspirates from ectopic thymic tissue yield a lymphoid population with a predominance of small lymphocytes, which can be particularly challenging to distinguish from true lymphadenopathy. However, thymic aspirates are characterized by a variable number of larger epithelial cells, and if flow cytometry is performed, there is a maturational spectrum from immature to maturing T-cells (Fig. 3.7).
Table 3.5
Mimics of lymphadenopathy in children and adolescents
• Thyroid lesions/neoplasms |
• Salivary gland lesions/neoplasms |
• Cystic head and neck lesions (e.g., branchial cleft cyst, thyroglossal duct cyst, other developmental cysts) |
• Extranodal inflammatory lesions (e.g., abscess) |
• Fibrous hamartoma of infancy |
• Pilomatrixoma |
• Mesenchymal lesions/neoplasms (e.g., lymphangioma/hemangioma, fat necrosis, lipoma, fibromatosis, solitary myofibroma, rhabdomyosarcoma) |
• Neural neoplasms (e.g., schwannoma, neurofibroma, ganglioneuroma) |
• Germ cell tumors (e.g., cervical teratoma) |
• Odontogenic or bone lesions (e.g., odontogenic cyst, fibrous dysplasia) |
• Thymic tissue or lesion (e.g., undescended thymus) |
• Benign soft tissue elements (e.g., skeletal muscle, adipose tissue) |
Fig. 3.6
Composite of mimics of lymphadenopathy in children and adolescents.
Fig. 3.7
Ectopic thymic tissue (Diff-Quik stain, high power). Thymic tissue can be present in the neck and mimic a lymph node clinically and cytologically. Although there is a predominance of small lymphocytes, larger epithelial cells are also present and flow cytometry or immunohistochemical stains can help to confirm the presence of immature and maturing T-cells.
3.4 Benign Entities
3.4.1 Reactive Lymphoid Hyperplasia
Clinical Features
Reaactive lymphoid hyperplasia (RLH), characterized by follicular hyperplasia, paracortical hyperplasia and/or sinus histiocytosis, is the most common cause of lymphadenopathy in the pediatric population, accounting for approximately 75 % or more of cases. The high incidence of RLH in this population is largely attributable to the repeated antigenic stimulation of naïve immune systems. On physical examination, benign, reactive lymph nodes usually measure less than 3 cm in greatest dimension and most commonly involve the head and neck, axilla, or inguinal region. RLH resolves spontaneously and can be followed clinically. However, lymphadenopathy that persists for more than 3–6 months or has features inconsistent with RLH may prompt an initial or repeat cytologic evaluation.
Cytological Features
RLH is characterized by a heterogeneous lymphoid population spanning the spectrum from immunoblasts to plasma cells, but dominated by small mature lymphocytes with round nuclei and condensed dark chromatin (Fig. 3.1). In addition, scattered tingible body macrophages, lymphohistiocytic aggregates, and follicular dendritic cells are usually seen.
Differential Diagnosis
The main diagnostic considerations include Hodgkin lymphoma, T-cell lymphoma, partial lymph node involvement by a lymphoid or non-lymphoid malignancy, post-transplant lymphoproliferative disorder, and early infection, as well as other possibilities (Tables 3.1, 3.2, and 3.3). Although rare in the pediatric population, some B-cell non-Hodgkin lymphomas, including marginal zone, low grade follicular, and T-cell rich large B-cell lymphomas, have a heterogeneous population of cells dominated by small cells. However, in contrast to RLH, the spectrum of cells in these malignancies is usually limited. Atypical cells should raise the possibility of a malignant process, but may be few in number in T-cell rich large B-cell lymphoma, Hodgkin lymphoma with a paucity of Reed–Sternberg cells, or partial replacement of a lymph node by a primary lymphoid or metastatic non-lymphoid malignancy. In some early infections, particularly mycobacteria and Bartonella, the characteristic granulomatous and/or neutrophilic inflammation may be absent or poorly developed, and therefore, aspirates from these lymph nodes may mimic non-specific RLH. A rare but important cause of reactive-appearing lymphadenopathy in the pediatric population is autoimmune lymphoproliferative syndrome (ALPS) . This inherited disorder is characterized by defects in Fas/CD95/Apo-1 mediated apoptosis, which lead to childhood onset of generalized lymphadenopathy, hypergammaglobulinemia, lymphocytosis, splenomegaly, and autoimmune phenomena. Flow cytometry performed on lymph nodes from ALPS patients shows an increase in CD4, CD8 double negative, T-cell receptor (TCR)-alpha beta T-cells, ranging from 27 to 54 % of mononuclear cells , and representing 51–78 % of alpha beta T-cells [9].
Pearls
Collection of additional material for ancillary studies, such as microbial cultures, special stains, flow cytometry, FISH, and immunohistochemical stains, should be considered when the clinical or microscopic features are concerning for infection, a lymphoproliferative disorder or a metastatic malignancy.
Use of a needle alone, without an attached syringe or suction (fine needle non-aspiration technique), can help to optimize control and sampling of small, mobile lymph nodes, and may also decrease anxiety for the patient.
3.4.2 Suppurative Lymphadenitis
Clinical Features
Acute suppurative lymphadenitis usually presents as tender, erythematous, superficial lymph nodes, and is most often due to infection with bacteria such as Staphylococcus, Streptococcus, and gram-negative organisms. Cat scratch disease due to Bartonella henselae infection should be considered, particularly if there is a history of a cat scratch or bite or simply the presence of a cat in the patient’s home environment. Although rare, fungal infections can also cause suppurative lymphadenitis. Empiric treatment with antibiotics results in resolution of acute lymphadenitis in many cases and therefore, cytologic evaluation is usually reserved for those cases in which the lymphadenopathy persists despite therapy.
Cytological Features
Aspirates from acute suppurative lymphadenitis yield yellow-tinged, thick, turbid material. Microscopically, numerous neutrophils, as well as variable numbers of lymphocytes and histiocytes, are present in a dirty background of granular and cellular debris (Fig. 3.8). In some cases, intracellular and/or extracellular microorganisms can be identified on routine stains, and are usually more apparent on modified Giemsa than on Papanicolaou-stained smears . The presence of granulomas in addition to suppurative inflammation is suggestive of cat scratch disease (Fig. 3.9) or mycobacterial infection. Special stains, such as Gram, methenamine silver, Steiner, Warthin–Starry, and acid fast, and/or an immunohistochemical stain for Bartonella may be helpful for demonstrating the presence of microorganisms.
Fig. 3.8
Acute suppurative lymphadenitis (Diff-Quik stain, high power). Aspirates from suppurative lymphadenitis show granular necrotic and karyorrhectic debris and neutrophils.
Fig. 3.9
Cat scratch disease (a, b. Papanicolaou stain, high power; c. H&E stain, medium power). Some lymph nodes with suppurative changes (a) also have granulomas (b). Acute suppurative and granulomatous inflammation should raise concern for cat scratch disease (c).
Differential Diagnosis
The main differential diagnostic considerations include necrotizing granulomatous lymphadenitis, systemic lupus erythematosus (SLE) , Kikuchi disease, lymph node infarction, and necrotic tumor. Although a dirty background with necrosis is characteristic of these entities, in contrast to acute suppurative lymphadenitis, neutrophils are usually absent, or if present, not a prominent feature. Other distinguishing features include the presence of granulomas in necrotizing granulomatous inflammation, hematoxylin bodies and LE cells in SLE, crescentic histiocytes in Kikuchi disease, and malignant cells in necrotic tumors.
