CHAPTER 18 Infectious diseases
Clinical aspects
Introduction
The widespread use of FNB for both palpable and impalpable lesions where the clinical and imaging differential diagnosis (DD) includes malignancy and sometimes infection has led to the diagnosis of infectious lesions. But with the increase in the number of immune compromised (IC) patients in developed countries, particularly due to the HIV epidemic and cancer therapy, FNB increasingly is used to assess skin, lymph node, lung and other sites where infection is the main diagnostic expectation.1,2 FNB can make the diagnosis of many specific infections on cytomorphology and special stains, and it also delivers material for the full array of ancillary studies including cultures, PCR and DNA analysis of other infections. The rapid diagnosis of infections, some of which cannot be cultured, can facilitate immediate treatment.
Now, with the gradual spread of FNB into the developing world where infections are the leading cause of morbidity and mortality, there has been a rapid if patchy increase in the use of FNB to make specific infectious diagnoses. FNB is minimally invasive, inexpensive, acceptable to patients, provides a rapid accurate diagnosis and immediate triaging for the most cost-effective selection of special stains and ancillary tests, and provides material for culture and the full range of ancillary tests. FNB is a very powerful diagnostic tool, especially where surgical resources and histopathological and microbiological laboratories are in short supply and grossly underfinanced.3 A cervical lymph node in a young adult that would, in subSaharan Africa, be treated expectantly as TB, can have an FNB that may show tuberculosis, metastatic carcinoma, lymphoma, reactive lymph node or branchial cyst. The FNB empowers the clinician to make the correct, often infectious, diagnosis, provides the best possible outcome for the patient and saves the medical system – which may be severely stressed by the AIDS epidemic, patient numbers and inadequate funding – the cost of surgical biopsy, hospital bed occupancy and inappropriate treatment
Place of FNB in the investigative sequence
The role of FNB is dependent on the body site and the facilities and expertise of personnel at particular institutions. In both the developed world and the four-fifths of the world where medical resources are limited, an inexpensive outpatient FNB can triage and, in the vast majority of cases, make a definitive diagnosis of any palpable lesion. FNB is the most efficient, least invasive and most cost-effective investigative procedure, particularly in cases where an infectious process is expected based on an integration of patient history and examination. This is exemplified by patients with suspected or known immune deficiency due to cancer, therapy or HIV disease.4,5
Specific sites
In the head and neck region after completion of a history and examination, which may include endoscopy of the upper aerodigestive tract, FNB of palpable lumps is the first line of investigation in all patients, especially the IC. The exact site of the lesion suggests the DD. In the preauricular, upper cervical and submental regions, acute or chronic sialadenitis,6,7 salivary gland neoplasms and a full range of lymph node lesions including reactive nodes, metastatic tumor, mycobacterial infection, lymphoma or other specific infection have to be considered. Rapid staining and immediate assessment of FNB slides is very powerful in this setting to direct selection of ancillary testing.
In the lower cervical and adjacent midline region, lesions of the thyroid, lymph nodes and rarely the parathyroids form the differential diagnosis. Specific infections of the thyroid due to tuberculosis, viruses and, less commonly, Aspergillus spp, Candida spp, Histoplasma capsulatum, Cryptococcus neoformans, Coccidioides, Pneumocystis jirovecii blastomycosis and Pseudallescheria have been reported in increasing numbers.8 In the posterior triangle lymph nodes and schwannomas, and in the suboccipital area lymph nodes with specific infections including toxoplasmosis, and trichilemmal cysts and other skin lesions need to be considered.
Skin nodules and palpable subcutaneous lesions are easily sampled by FNB. Pyogenic abscesses and infections such as tuberculosis9 are easily differentiated from tumor metastases, and, in the HIV population, from Kaposi’s sarcoma. Both superficial and deep fungal infections can be diagnosed by FNB and, especially in the IC, may represent disseminated fungal infection due to Aspergillus spp, Cryptococcus neoformans, histoplasmosis, blastomycosis,10 sporotrichosis and Candida spp,11 or one of the increasing number of other reported fungal infections producing subcutaneous nodules or mycetomas, including, Phialophera parasiticus, Sporothrix schenkii, Cladosporium spp, Exophiala jeanselmei12 and Microsporum canis.13 Actinomyces producing actinomycetomas, and rhinosporidiosis,14 filariasis,15 myaisis,16 leishmaniasis and leptosporosis all occur in the skin. The tuberculoid, borderline and lepromatous variants of leprosy, as well as neuritic and cystic lesions, can all be diagnosed.17 FNB of cellulitic skin to diagnose surgical wound skin infections18 and Buruli ulcers19 by direct smears and culture have been recommended. Skin nodules due to myaisis are rare but eminent FNB targets (Fig. 18.1).
![image](https://i0.wp.com/basicmedicalkey.com/wp-content/uploads/2017/06/B9780702031519000189_f018-001-9780702031519.jpg?w=960)
Fig. 18.1 Cutaneous myaisis
Dipteran larva in background of pus from 23-gauge FNB of skin abscess (HE, ×600).
(Courtesy Dr Peter Pogany, Budapest, Hungary)
FNB without prior imaging is the first-line diagnostic approach for suspected breast abscesses yielding suppuration and a wide range of common bacteria and other agents including brucellosis20 and can assist in the drainage of the abscess. Cultures are mandatory. Repeat FNB is required if a significant palpable or ultrasound lesion remains after treatment because very occasional high-grade carcinomas can be associated with obscuring necrosis, neutrophilic infiltrate or multinucleated giant cells (MNGC) and a careful assessment of any inflammatory smear is required to ensure these unusual but rare carcinomas are not missed. Breast FNB may produce granulomatous material where mycobacterial and other infections must be excluded by culture.21
Lesions in the testis and scrotum including mycobacterial orchitis and epididymitis can be sampled by FNB to allow differentiation from neoplasms with no risk of a neoplasm seeding in the FNB track and jeopardising possible surgery.22
FNB of bone, soft tissue and skeletal muscle lesions,23 when palpable or under ultrasound direction, is a straightforward procedure and the diagnosis of osteomyelitis due to tuberculosis24 or other infectious agents can be made and confirmed on culture.25
In most developed countries, FNB of central lung lesions, mediastinal, hilar, coeliac, peripancreatic and porta hepatis lymph nodes and pancreatic lesions is now performed under endoscopic ultrasound or endoscopic bronchial ultrasound direction. Percutaneous FNB of peripheral lung, liver and splenic lesions also yield infectious diagnoses, and may be the diagnostic test of choice, for example in paediatric peripheral lung lesions.26
In the liver, amebic and tuberculous abscesses, schistosomiasis27 and pyogenic abscesses due to fungi, staphylococcus, streptococcus, and Gram-negative bacteria including Klebsiella spp and Escherichia coli can be diagnosed. The use of albendazole and steroids as cover for the potential but very low risk of anaphylactic shock due to spillage of hydatid cyst contents during FNB should be considered if hydatid disease is suspected in an FNB of any site.28
In the pancreas, tuberculosis and infections diagnosed by EUS FNB have been increasingly reported in cases suspected of carcinoma.29 EUS-FNB also accesses the adrenal glands, where suspected metastases have been proven to be tuberculosis, cryptococcosis and disseminated histoplasmosis.30
In the lung, FNB is frequently used to distinguish tuberculosis or Gram-negative or -positive bacterial abscesses from carcinomas. Aspergillosis, mucormycosis,31 candidiasis and cryptococcosis, as well as, P.jirovecii in the HIV population, and CMV, coccidioidomycosis32 and parasites including paragonamiasis,33 amebiasis, hydatid disease and microfilariasis have all been reported.
In cases of splenomegaly and investigation of splenic lesions found on imaging, FNB is best performed under ultrasound guidance. Diagnoses include tuberculosis, lymphoma and other lesions but uncommon infections such as leishmaniasis should be considered.34
FNB of cerebral cortex lesions via burr holes can be used to diagnose toxoplasmosis, CMV and fungal infections35 in the DD with metastases and primary brain tumors.36
Technical considerations
When a cystic lesion or abscess is suspected it is recommended that a needle on a syringe should be used, creating a ‘closed’ system to avoid infective fluid spurting from the needle hub, and to assist in obtaining several milliliters of pus for culture. But using the needle by itself gives more sensitivity for FNB of palpable lesions, and can be used for a second pass of any residual mass after draining a cyst, or for solid and small lesions, especially skin nodules. Needles of 22 to 27 gauge are recommended for lymph nodes and skin lesions. If pus or necrosis is found and material is needed for extra slides, stains and cultures, a 22 gauge or 23 gauge will produce more material. The diagnostic yield of the cultures is higher with more material, so repeat needling using all the material for culture is recommended rather than just saline rinses of needle and syringe.37
A cell block should be prepared in almost all cases from saline rinses of the needle or ideally from separate needling, for H&E, special stains, immunoperoxidase studies (IP) and electron microscopy where required. In TB or HIV endemic areas or where the patient is thought to be IC, direct inoculation into culture bottles can be used.38 In cases such as liver abscesses where anaerobes are expected, pus should be placed directly into appropriate microbiologic containers. If the DD is lymphoma, especially in lymph nodes, lungs or spleen, FNB material should be placed into normal saline, Hanks medium or similar for flow cytometry and cytogenetic and gene rearrangement studies.
Immune compromised patients
FNB is extremely useful in the ever-increasing number of IC patients, including patients on long-term steroids, undergoing treatment for solid and hematologic malignancies, solid organ transplant recipients and HIV-positive persons.4,5 The successful role of FNB has continued into the era of highly active antiretroviral therapy (HAART).39 The typical inflammatory reactions to common infectious agents may be both deficient and atypical, and unusual and opportunistic infections may be present, making culture of FNB material mandatory.4 More than one infection may be present, for example CMV and bacterial infections in transplant patients.
Cytological findings
Criteria
In IC patients with neutropenia, a thin proteinaceous background may contain scant or no neutrophils and an organism must be sought with special stains and cultures. In AIDS patients, there may be plentiful plump histiocytes with cell debris and neutrophils resembling acute bacterial infections, but plentiful curved bacilli will be seen as negative images in the background and cross-hatched in macrophage cytoplasm (See Fig. 18.5). Culture and drug sensitivity testing is required.
In fungal and cat scratch disease,40 suppurative granulomas with neutrophils interspersed among the epithelioid histiocytes in the granulomas may be present (Fig. 18.2).
![](https://freepngimg.com/download/social_media/63059-media-icons-telegram-twitter-blog-computer-social.png)
Stay updated, free articles. Join our Telegram channel
![](https://clinicalpub.com/wp-content/uploads/2023/09/256.png)
Full access? Get Clinical Tree
![](https://videdental.com/wp-content/uploads/2023/09/appstore.png)
![](https://videdental.com/wp-content/uploads/2023/09/google-play.png)