CYTOLOGY OF INFLAMMATION

41 CYTOLOGY OF INFLAMMATION



Rick L. Cowell, Theresa E. Rizzi, James H. Meinkoth



1 What is neutrophilic inflammation?


Preparations in which greater than 70% to 75% of the cells are neutrophils are referred to as having neutrophilic inflammation (Figure 41-1). Suppurative inflammation and purulent inflammation are other terms for a marked predominance of neutrophils (>85%). The terms “active” or “acute” inflammation are occasionally used for this type of cellular reaction, but in this case the terms relate only to the cell type and not to a time frame.


image

Figure 41-1 Septic neutrophilic inflammation. Aspirate of mass from a dog showing high numbers of degenerate neutrophils and mixed bacteria. Bacteria are present both intracellularly and extracellularly. (Wright’s stain; 250×.)



2 What causes neutrophilic inflammation?


The most common cause of neutrophilic inflammation is a bacterial infection. Other organisms (e.g., Sporothrix) and many noninfectious disorders (e.g., necrotic areas in tumors, immune mediated disorders) can also cause neutrophilic inflammation.



3 What is pyogranulomatous inflammation?


Preparations with an inflammatory population that contains both neutrophils and a prominent fraction of macrophages (15% to 50% macrophages) are referred to as showing pyogranulomatous inflammation (Figure 41-2). The term “chronic active inflammation” is sometimes used for this type of inflammatory reaction, although it is falling out of usage because it relates only to the cell reaction and should not be interpreted in relation to a time frame. Multinucleated giant cells, reactive fibroblasts, and lymphocytes may also be present in pyogranulomatous inflammation.


image

Figure 41-2 Pyogranulomatous inflammation. Aspirate from cutaneous lesion on a dog showing many neutrophils and moderate numbers of macrophages in stippled mucoprotein background. (Wright’s stain; 250×.)



4 What are the diagnostic implications of pyogranulomatous inflammation?


Pyogranulomatous inflammation suggests a cause other than “routine” bacterial infection. Fungal infections (e.g., blastomycosis), higher bacteria (e.g., Actinomyces), mycobacteria, protozoa, and noninfectious disorders (e.g., foreign bodies, necrosis) are common causes of pyogranulomatous inflammation.



5 What is granulomatous (chronic) inflammation?


Preparations in which greater than 50% of the cells are macrophages are often referred to as having granulomatous inflammation. The term “chronic inflammation” is occasionally used, but this term relates only to the cell types present and does not indicate a time frame; thus it is falling out of usage. Multinucleated inflammatory giant cells, reactive fibroblasts, and lymphocytes may also be seen in granulomatous inflammation.



6 What causes granulomatous inflammation?


Causes of granulomatous inflammation are similar to those that cause pyogranulomatous inflammation (e.g., fungal, mycobacteria, protozoa, foreign bodies, necrosis).



7 What is eosinophilic inflammation?


Preparations in which large proportions of the cells are eosinophils (>10%-20%) are often referred to as showing eosinophilic (or mixed) inflammation. The other cells present are often an admixture of neutrophils, macrophages, mast cells, and lymphocytes. Occasionally, eosinophil granules may stain tan or muddy brown in tissue preparations, making them more difficult to recognize. However, their distinct granules allow for eosinophil identification. Also, neutrophils occasionally have a fine eosinophilic stippling in thick exudates and should not be confused with eosinophils.



8 What causes eosinophilic inflammation?


Common causes of eosinophilic inflammation include immune/allergic reactions, parasitic disorders (e.g., lungworms, some arthropod bites), certain fungal infections (e.g., phycomycosis), and some neoplasias (e.g., mast cell tumors).



9 What is lymphocytic or lymphocytic/plasmacytic inflammation?


Preparations from nonlymphoid tissue that contain a large proportion of mature lymphocytes (small lymphocytes and plasma cells) are referred to as having lymphocytic or lymphocytic/plasmacytic inflammation. This is differentiated from cutaneous lymphoma (lymphosarcoma) in that cutaneous lymphoma usually consists almost totally of large lymphoblasts. When small cell lymphoma is present, biopsy and histopathology for the evaluation of architecture generally are needed to obtain a definitive diagnosis.



10 What causes of lymphocytic or lymphocytic/plasmacytic inflammation?


Lymphocytic or lymphocytic/plasmacytic inflammation occurs with some injection site reactions, some insect bites, feline stomatitis/gingivitis, and lymphocytic/plasmacytic gastroenteritis.



11 What are degenerative neutrophils?


Degenerative neutrophils are neutrophils that have lost their ability to control water homeostasis and are undergoing hydropic degeneration. As water diffuses into the cell, it causes the cell to swell. Water also diffuses into the nucleus through nuclear pores and causes the nucleus to swell, fill more of the cytoplasm, and stain homogeneously eosinophilic.



12 What is the diagnostic significance of degenerative neutrophils?


The presence of degenerative neutrophils suggests a bacterial cause because these changes are caused primarily by toxins produced by bacteria (e.g., endotoxin). However, the absence of degenerative neutrophils does not rule out a bacterial cause because bacteria may be present in low numbers and some bacteria produce low levels of toxin. Therefore, when degenerative neutrophils are present, suspicion of a bacterial infection is increased. Although all cell types are subjected to the same toxin, degenerative change is evaluated only in neutrophils. Also, degenerative changes can be induced by autolysis (rot). Therefore, samples made from dead animals or samples collected and held for a long time before smears are made may show degenerative as well as pyknotic changes.



13 What are nondegenerative neutrophils?


Neutrophils with tightly clumped, basophilic nuclear chromatin are termed nondegenerative neutrophils. A few or many neutrophils may be hypersegmented or pyknotic (nuclear chromatin broken into tight, round spheres), representing aging changes that may occur in vivo or in vitro.



14 How do bacteria appear cytologically, and what is their interpretive significance?


With the routine blood stains (e.g., Wright’s, Diff-Quik, Dip-Stat), all bacteria (gram positive and negative) stain blue to purple (basophilic); the few exceptions include mycobacteria that do not stain. Intracellular bacteria indicate bacterial infection (primary or secondary), whereas extracellular bacteria may represent bacterial infection or contamination. Bacterial infections often have bacteria intracellularly and extracellularly, whereas contamination has only extracellular bacteria. Also, the bacteria should be evaluated to determine if only one population exists (e.g., monomorphic population of cocci or rods) or if a mixture of rods and cocci or variably sized rods exists (e.g., pleomorphic population). Pleomorphic bacteria are common with, for example, infections of gastrointestinal origin and bite wounds.

Related posts:

  1. ERYTHROCYTE DISORDERS
  2. OVERVIEW: HEMOSTATIC COMPONENTS AND DISORDERS
  3. INTERPRETATION OF THE LEUKOGRAM
  4. AVIAN BIOCHEMICAL ANALYSIS

Stay updated, free articles. Join our Telegram channel
Tags:
Aug 26, 2016 | Posted by in INTERNAL MEDICINE | Comments Off on CYTOLOGY OF INFLAMMATION

Full access? Get Clinical Tree
Get Clinical Tree app for offline access