Page 346 - Concise Pathology for Exam Preparation ( PDFDrive )

12 Haematology 331

Laboratory Diagnosis

• Anaemia with macrocytosis and anisocytosis; RBCs may be dimorphic in RARS (both
hypochromic and normochromic cells seen)
• Thrombocytopenia (platelets vary in size and some appear hypogranular)
• The WBC count may be normal, increased or decreased. Hypogranular or agranular
granulocytes and neutrophils with bilobed Pelger Huet anomaly may be seen.
• Marrow is normocellular to hypercellular. Erythroid precursors show dyserythropoiesis.
Immature myeloid cells are present in less well-differentiated subgroups (refractory
anaemia with excess of blast cells and refractory anaemia in transformation).

LYMPHORETICULAR SYSTEM

Nonneoplastic Proliferations of Lymph Nodes
Q. What is reactive lymphadenitis?
Ans. Infections and noninfectious inflammatory stimuli can cause lymphadenitis, which
may be classified as:

Acute Nonspecific Lymphadenitis
• May be confined to a local group of lymph nodes draining a focal infection
• May be generalized in systemic bacterial or viral infections
Gross Morphology
• Tender and fluctuant in case of abscess formation
• Involvement of the overlying skin can produce draining sinuses
Microscopy
• Large germinal centres
• A neutrophilic infiltrate is seen about the follicles and within lymphoid sinuses in pyo-
genic infections
• In severe infections, centres of the follicles undergo necrosis resulting in formation of an abscess

Chronic Nonspecific Lymphadenitis

Assumes three patterns depending on the causative agent, namely, follicular hyperplasia,
paracortical hyperplasia and sinus histiocytosis
1. Follicular hyperplasia
(a) Associated with infections and inflammations, which activate B cells
(b) Follicles are enlarged with prominent germinal centres.
(c) Cells in the reactive follicles include activated B cells, scattered macrophages con-
taining nuclear debris (tingible body macrophages) and follicular dendritic cells
(d) May be confused with follicular lymphomas
Features favouring a diagnosis of follicular hyperplasia over a follicular lymphoma
• Preservation of lymph node architecture with normal areas between germinal centres
• Variation in shape and size of lymphoid nodules
• Mixed population of lymphocytes at various stages of differentiation
• Prominent phagocytic and mitotic activity in germinal centres
2. Paracortical hyperplasia
(a) Reactive changes in the T-cell regions
(b) Encountered in viral infections (EBV), following vaccinations (small pox) and in
drug reactions (phenytoin)
3. Sinus histiocytosis
(a) Distension of the lymphatic sinusoids
(b) Hypertrophy of lining endothelial cells and increase in the number of macrophages
(c) Often seen in lymph nodes draining cancers (immune response to tumour and its
products)

mebooksfree.com