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The approach to the cytological diagnostic of tumours and pseudotumoral lesions in paediatrics is based essentially on the use of fine-needle biopsy (FNB). Being an inexpensive low invasive technique with a high accuracy and diagnostic briefness FNB is regarded ideal to be applied in the paediatric setting and particularly in underdeveloped countries.
Cytogenetic and molecular studies provide pivotal biologic and clinical insights into paediatric pathology. The understanding of the potential role of tumour biology settled a huge improvement in therapies, identifying therapeutic risk groups, and achieving better outcomes while reducing unwarranted late effects and morbidity. The use of a rapid, safe and accurate approach allowing the collection of enough material for genetic testing underlines the importance of FNB in the initial assessment of paediatric tumours. On the other hand, most treatment schemes in paediatric solid tumours use preoperative chemotherapy in tumours not amenable to immediate resection. So the possibility of association to complementary and sophisticated techniques such as flow cytometry, FISH, and PCR among others has enhanced the diagnostic power of this technique.
The advantages provided by FNB are optimized in the setting of a multidisciplinary team where cytologist, clinician and radiologist play leading tasks. Nowadays both in paediatric oncology as in oncology in general, the pathologist must acquire basic clinical and imaging knowledge’s.
In an initial approach to diagnosis, the main goals of FNB are to separate benign from malignant clinical settings, and to proceed for a prompt therapy avoiding needless surgeries, longer recovery times, and lengthy hospitalizations. Cancer is rare among those younger than 20 years of age; nevertheless a lump or a mass in a child is always a cause of concern and should be subjected to clinical evaluation.
In Europe about 15,000 children under 14 years are diagnosed with cancer each year.
Cancer in children encompasses a spectrum of different malignancies varying with the histology type, age, location, race, and gender (Fig 1 and 2).
We review essentially the cytological patterns that characterize the most frequent tumours in childhood.
PLANNING AND CARRYING OUT THE FINE NEEDLE BIOPSY PROCEDURE
The multidisciplinary approach is also crucial in the correct planning of the biopsy. The most probable informative areas of the mass should be chosen to allow the most accurate diagnosis. It is critical that the pathologist has the perception of the numerous tissues crossed by the needle, that despite of the use of mandrel needles, are usually dragged on its way and may turn as confounders. It is sometimes important to collect material from the neighbouring areas in order to compare with the tumour sample; this is particularly helpful in well differentiated hepatic tumours.
According to our experience, FNB should be performed preferably without aspiration, using a 25 gauge needle. Depending on the morphological features of the lesion (marked vascularization with risk of haemorrhage or marked desmoplasia) thinner (27 gauge) or larger (23 gauge) needles should be used. The mandrel needles enable to split the collected sample for various purposes, controlling the amount of ejected material from the needle. Each pass should collect material for at least two or three smears, and rinse to one or two PBS/RPMI Eppendorf tubes. Despite these advantages, mandrel needles are longer and more difficult to control.
Performing FNB in children is not different from a similar procedure in an adult. However several points should be considered to minimize the discomfort with the use of some basic rules, which will prevent some of these difficulties:
1 – FNB should be carried out with time and serenity and tranquillity should be encouraged to the parents and the child;
2- Far more frequently than adults, children require sedation for a variety of procedures or imaging tests, usually to access deep or less easily reached locations. When dealing with a probable malignant neoplasm and scheduling for immediate chemotherapy requiring a central venous catheter, or bone marrow biopsy for clinical stage evaluation, FNB should be performed in an operating theatre under general anaesthesia. This procedure allows a number of invasive medical procedures, saving anaesthetic;
3 – Rapid on-site evaluation (ROSE) should be used whenever possible. ROSE also has an important role to assess sample adequacy, and allow the collection of additional samples for ancillary studies. Needle rinsing sample from lymphoid lesions can be used for flow cytometry (FC), evaluating potential lymphoproliferative Material can be obtained to perform a cell block or cytospins can be performed later in the laboratory for histochemical, immunohistochemical, and molecular studies. Microbiologic cultures can be performed from lesions that appear to be inflammatory /infectious.
PEADIATRIC NON TUMOURAL LESIONS
In children, the most frequent non-tumour lesions target of FNB are of infectious cause, and often arise as a persistent lymphadenopathy. FNB should preferably be restricted to cases with a persistent enlarged lymph node or strong clinical suspicion of a specific infection or neoplasia, however in several situations it also is useful to reassure the parents’ and the physician´s fears of malignancy in a safe, timely, and cost-effective manner. Consequently a reactive cytological diagnosis is frequent. Other frequent cytological diagnosis are suppurative lymphadenitis granulomatous or not, or lymphadenitis due to mononucleosis.
We will not address these subjects that will be addressed elsewhere in “Lymph node”