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Aspiration Cytopathology of Lymph Nodes and Lymphoproliferative Neoplasms
Paul E. Wakely, Jr.
Click on any thumbnail images for an enlarged view of that slide
A 32 y/o woman presents with an enlarged 2.0 cm. slightly firm right cervical
lymph node. The node has been present for about 6 weeks. She complains of no constitutional symptoms.
A 12 y/o girl is seen in the clinic with a 1.5 cm. right axillary node which was
noted by her mother 3 weeks earlier. The mass has increased slightly despite antibiotic therapy. There
are no skin lesions.
A 25 y/o female veterinary medicine student presented to clinic with a 4 cm. non-tender left neck
mass. The mass has been present for 3 weeks according to her. She has no complaints of fever or weight
loss.
A 17 y/o young man presents with a 1.5 cm. right posterior cervical lymph node of unknown duration.
He complains of an upper respiratory infection, and a slight fever.
A 44 y/o woman presents with enlarged cervical, axillary and inguinal lymph nodes which she states
appeared about four months ago. FNA biopsy was performed on an enlarged cervical lymph node.
A 69 y/o man presents with a 2.0 cm. left posterior cervical lymph node of unknown duration. No
prior medical history.
A 29 y/o woman underwent CT guided FNA of a 4 cm. paratracheal mass.
A 15 y/o male presented to the emergency room with wheezing and difficulty breathing. Physical
examination revealed a 4 cm. midline neck mass.
A 47 y/o man complained of a lump in his neck which has been present for about 2 weeks. Physical
examination reveals a 2 x 3 cm. firm left upper cervical lymph node.
Objectives
At the end of the course, participants should be able
to:
 | Recognize and differentiate the cytopathology of various lymphoid neoplasms and non-neoplastic lesions of lymph nodes. |
| Identify cytopathologic imitators of malignant lymphoma and various non-lymphoid lesions metastatic to lymph nodes. |
| Define the application of immunophenotyping to the cytopathologic diagnosis of malignant lymphoma. |
| Discuss the limitations of aspiration cytopathology as applied to lymph nodes and lymphoid malignancies. |
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INTRODUCTION
Use of the fine needle aspiration (FNA) biopsy technique to understand the nature of lymph
node enlargement remains relatively underutilized in North America except in select medical centers.
Rationale for sampling an enlarged lymph node with a thin gauge needle is to determine the
cause of adenopathy. In contrast to surgical biopsy, FNA:
| does not involve an incision into the skin |
| does not require the trappings necessary for a surgical procedure |
| functions to extract cellular material that can be smeared onto glass slides for microscopic evaluation as well as rinsed in balanced salt solution, or a fixative for possible ancillary immunophenotyping or molecular studies. |
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Obviously, the intent is not to remove the entire lymph node or even obtain tissue fragments from the
node as a core needle biopsy does. This method of tissue sampling creates its own limitations (discussed
later). Table 1 shows some of the similarities and differences between FNA
and surgical biopsy.
The guiding principle in the interpretation of aspirates is identical to that of surgical
pathology: amalgamate the clinical picture with the microscopic details
combined with any necessary ancillary studies to generate a diagnosis (Frable, 1989). Aspiration
cytopathology of lymph nodes is nearly always a diagnostic, not a screening test. In truth, FNA biopsy
has a much closer kinship to surgical (tissue) pathology than to exfoliative cytopathology.
Table 1. Lymph Node - Surgical Biopsy vs. Fine Needle Aspiration Biopsy
| | Excisional Surgical Biopsy | FNAB |
| Material obtained | Tissue | Cells |
| Cost | Relatively expensive | Much less expensive |
| General anesthesia | Sometimes necessary | Unnecessary |
| Equipment needed | Variable, can be extensive | Minimal |
| Sampling error | Rarely a problem | Always a possibility |
| Complications | Uncommon | Rare |
| Scar/Sutures | Normal consequence | Never occurs |
| Pathologist confidence | Expertise widespread | Expertise limited |
| Insufficient diagnostic material | Almost never | Not uncommon; technique dependent |
Immunophenotyping/molecular
studies of pathologic material | Possible | Possible |
FNA of deep lymphadenopathy is the realm of interventional radiology. Who should perform
superficial lymph node FNA? - controversial, ultimately decided by local
conditions and traditions. FNA can become a "turf" issue with surgeons and clinicians even if fiscal
motives are not a source of contention.
Major advantage for the pathologist who does perform the FNA:
| becomes "visible" to clinicians; more easily identified as an important part of the clinical team. |
| can incorporate clinical findings/history along with the cytomorphologic features into the final diagnosis in a manner that cannot be done when one is merely sent the slides accompanied by a (usually limited) clinical history. |
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Reports from the past 15-20 years have documented that the percentage of unsatisfactory or
less than diagnostic smears is less when performed by a pathologist/interpreter than by a
clinician/surgeon who does not interpret their own smears. Major deterrent to a pathologist driven
FNA service:
| the amount of time it consumes in a busy FNA practice. This is particularly acute for those individuals without the luxury of residents and fellows. |
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Advantages and Limitations
| All examples of superficial lymph node enlargement in an adult are an immediate source of concern unless a cause is clinically evident. |
| FNA is readily accepted by the majority of patients, and is a direct route toward explaining the lymphadenopathy. |
| Pediatric lymph node enlargement not uncommon; may be watched for a period of a few weeks. Many treated empirically with antibiotics. |
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If adenopathy persists, however, the pediatrician is faced with the clinical dilemma of
either continued observation with the risk that treatment for a serious illness may be delayed, or
subjecting the child to open (and possibly unnecessary) biopsy with the risks and cost associated with
that procedure. FNA is thus a desirable tool to apply in both adult and pediatric situations.
Several positive consequences accompany lymph node FNA. One of these is that an FNA can
document that the mass in question is indeed a lymph node. Not all masses - particularly those in the
head and neck - which are clinically thought to represent lymphadenopathy are in fact lymph nodes (Table 2).
Table 2. Neck Masses Potentially Confused As a Lymph Node by Physical
Exam
| Thyroid nodule/neoplasm |
| Soft tissue tumor |
| Inflammatory lesion: fat necrosis, abscess, scar |
| Skin appendage tumor |
| Paraganglioma |
| Cyst: branchial cleft, epidermal, thyroglossal |
| Salivary gland neoplasm |
| Skeletal structure: cervical rib |
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The advantages of lymph node FNA are listed in Table 3.
Table 3. Benefits of Lymph Node Aspiration
| Triage of Patient with Lymphadenopathy |
| |  | Confirms that the mass is lymphoid tissue. |
| | | Can preselect those patients without a prior medical history of cancer that would require surgery (e.g. Hodgkin lymphoma) from those where it can be avoided (reactive hyperplasia, some non-Hodgkin lymphomas, many infectious conditions, metastatic tumor). |
| | | Helps to focus laboratory testing for clinician thus resulting in a more informed and economical workup (e.g. granulomatous disease). |
| | | May suggest a primary site if metastatic tumor is found. |
| | | Provides material for culture if infectious process suspected. |
| Effective Diagnostic Tool |
| | | Rapid turnaround time (minutes for a preliminary interpretation). |
| | | High diagnostic sensitivity and specificity for experienced observers. |
| | | Ability to sample multiple nodes if necessary. |
| | | Minimal trauma. Complications are rare. |
| | | Low cost. |
| | | Capable of obtaining cells for immunotyping, and other ancillary tests. |
| Efficacious in the Cancer Patient |
| | | Preserves lymph node architecture if surgical biopsy is required. |
| | | Documents metastasis in a known cancer patient. |
| | | Can confirm recurrence or transformation to a higher grade lymphoma in a patient with known malignant lymphoma. |
| | | Helps in staging of tumor. |
| May substitute for Surgery in Certain Clinical Circumstances |
| | | Unacceptable surgical candidate (e.g. paratracheal/mediastinal adenopathy). |
| | | When conservative management is more appropriate. |
| | | When cytomorphology plus immunophenotyping is diagnostic. |
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Some of the detractors of lymph node aspiration cytopathology continue to point to its
inability to produce results equal to those obtained with tissue pathology. In most clinical scenarios,
however, the clinician is just trying to find out what has produced this mass, and therefore has a
clinical diagnosis of "rule out malignant neoplasm". More realistic comparison is generally not between
the cytologic smear diagnosis and tissue diagnosis; rather it is between the smear diagnosis and clinical
diagnosis. It remains true that in many instances the tissue diagnosis of lymph node pathology remains
the "gold standard", but in some diseases FNA cytopathology is as good as a tissue diagnosis, and in some
instances (e.g. lymphoblastic lymphoma) a superior substitute.
Smears can be evaluated in a matter of minutes to determine whether diagnostic material is
present before the patient leaves the room. This also means that the clinician can be informed of the
nature of the disease process shortly after an FNA. This allows one to reduce the anxiety of patients
and/or parents (which often exists in these situations) if the condition is benign, or to convince them
of immediate therapy or further procedures if it is not.
Major contraindication to FNA of a superficial lymph node: a severe coagulation disorder.
Even this is only a relative contraindication, and FNA may be attempted if appropriate blood products
temporarily correct the situation. Hematoma formation is the only "common" complication of superficial
FNA. Extremely unusual complications:
| hemorrhage, fibrosis, and partial or total infarction of lymph nodes |
| FNA rarely precludes histologic analysis if the node is subsequently excised. |
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Recent report of 3 cases of complete lymph node infarction post-FNA demonstrated that
immunohistochemical staining of the necrotic tissue sections is useful and can confirm the FNA
diagnosis.(Diagn Cytopathol 2001;25:104-07)
Caution: One must be extremely careful
when aspirating a deep axillary, low cervical, or supraclavicular lymph node because the possibility of
pneumothorax (admittedly low) does exist. Parenthetically, pneumothorax is always a risk whenever
deep FNA of enlarged mediastinal lymph nodes or a mediastinal mass is attempted.
Even with all these positive attributes, lymph node FNA remains an imperfect test. Major
shortcomings:
- grouped under the heading of sampling error secondary to a.improper technique, b.partial lymph node involvement by a malignancy, c.partial/complete fibrosis of a node such as can develop with Hodgkin lymphoma, or a sclerosing mediastinal non-Hodgkin lymphoma. When fibrosis prevents the extraction of diagnostic cells from their collagen matrix one is left with hypocellular smears with few if any diagnostic cells.
- inability of FNA biopsy to evaluate lymph node architecture. This can hamper the recognition of specific lymphadenopathies where evaluation of spatial relationships is required.
- pathologist "comfort level". Because the amount of time spent in residency training in cytopathology (in North America) is much less compared to the amount spent in surgical pathology, confidence in FNA diagnoses among many pathologists is less than optimal. Thus, it is much easier for many pathologists to suggest examination of the enlarged lymph node after it is surgically excised.
These and other causes for inconclusive or incorrect results from FNA are listed in Table 4.
Table 4. Lymph Node FNA - Limitations
| Sampling error secondary to: |
| | | Improper/poor technique. |
| | | Lymph node fibrosis |
| | | Excessive necrosis, inflammation, or blood. |
| | | Partial involvement of lymph node by the lesion. |
| | | Small or deep seated lymph node. |
| | | Lymph node or mass too large. |
| | | Failure to obtain cells for ancillary studies, e.g. immunophenotyping, culture, molecular techniques. |
| Inability to evaluate Architecture/Vascular pattern |
| | | Examples: Progressive Transformation of Germinal Centers, Vascular transformation of lymph node sinuses, etc. |
| | | Subtyping of some lymphoid disorders not possible |
| Interpretation error: |
| | | Limited experience/expertise. |
| | | Attempting to make specific diagnoses on limited or poorly preserved material. |
| A negative diagnosis does not possess the same degree of assurance as a positive diagnosis. |
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| FNA is not meant to replace clinical judgment. |
| Because of aforementioned potential sources of error, one should always be cognizant that a negative result does not unequivocally mean the absence of disease; any lymph node that is clinically suspicious, but cytopathologically interpreted as benign requires further evaluation and probably surgical excision. |
| FNA, though very useful in a patient with a discrete mass, is rarely informative when performed on patients with only a vague "swelling" or induration of an area. |
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Table 5. Lymph Node FNA – Diagnostic Possibilities
| Reactive Lymphoid Hyperplasia |
| Inflammatory/ Infectious Disease |
| Benign Lymphoproliferative Disorder |
| Neoplasms Arising in Lymph Node |
| Neoplasms Metastatic to Lymph Node |
| | | Carcinoma, Melanoma, Sarcoma, Germ Cell Tumor |
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Table 6. Lymph Node FNA – Danger Zones
| Lower Cervical Node |
| Deep Supraclavicular Node |
| Deep Axillary Node |
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Accuracy Data
| FNA literature has demonstrated high rates of sensitivity and specificity in the recognition of benign and malignant lymph node aspirates. |
| True comparisons among various studies of lymph node aspiration accuracy are difficult because of: a.) the marked variation in which the data is presented in each article, b.) how cells are collected in each institution, c.) how many punctures are made into a lymph node(mass), d.) level of experience of the aspirator, e.) whether these are superficial or deep seated nodes, i.e. radiologist procured, and f.) whether authors consider diagnoses of atypical cells clinically useful information. |
| Details of accuracy regarding lymphomas are presented in that section. Nonetheless, the collective experience from published data appears to show that lymph node cytopathology has proven clinical utility in the above named categories (table 5). |
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Technique
FNA is well tolerated by the majority of adults. Young children and infants must be
restrained. Children old enough to understand the procedure are generally cooperative. I make it a
point not to show the inquisitive child any equipment, or the needle until after the procedure
because of the anxiety it generates. Since many excellent monographs, chapters, and texts exist
regarding FNA biopsy technique, only a brief overview is supplied here.
I generally do not use any anesthetic prior to FNA, but some centers use local anesthesia
either with a topical cream or superficial lidocaine injection. Some individuals go to great lengths
with excessive cleansing of the skin surface, use of sterile towels or other coverings and expensive
prepackaged trays that contain the equipment needed to accomplish the task. We take a more simplistic,
economical, and we believe just as efficacious an approach by merely using alcohol swabs to cleanse the
area for superficial aspirates. If anesthetic is injected, it should always be done so at the periphery
of the mass rather than on or into the mass to avoid re-aspirating anesthetic during the FNA which can
potentially dilute the cell sample, or even alter cell morphology. Children undergoing radiographically
guided (usually computerized tomography) FNA of transabdominal or transthoracic lymph nodes or masses are
routinely sedated. Adults generally are not.
The aspiration procedure itself may be performed with the needle attached to a syringe so
that a vacuum is applied, or the aspiration may be performed using only the needle. For lymph node
aspirates both methods are probably just as effective. I find myself using the needle-only technique for
small (<1 cm.) lymph nodes, or those that are difficult to immobilize. I am generally able to procure
more cells when using a syringe with vacuum than without it.
The number of times a mass should be aspirated needs to be individualized. As a general
rule, I make at least three separate "passes"(needle puncture with aspiration) into a mass, sometime
more. A single fine needle aspiration biopsy procedure consists of the following:
FNA Biopsy Technique
Insert needle into the mass – pull back on syringe for vacuum - move needle in a back and forth
motion within mass - watch for material in hub of syringe - release vacuum shortly after material seen in
hub of syringe - remove needle from patient - make smears - rinse the needle into balanced salt solution.
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With each FNA biopsy I go back to just a slightly different area of the mass if it is
large enough, and repeat the procedure. The angle of direction at which the needle is inserted is
slightly different with each "pass" in order to sample the mass as thoroughly as possible. If the mass
turns out to be a cyst, I try to aspirate it entirely, and then palpate the area to determine if a
residual mass exists. If it does, one should re-aspirate this mass. Generally, the first aspiration is
the best. The second and third attempts often have more blood. Recall that lymphoid tissue/cells are
fragile, and easily can be crushed with nuclear smearing if too much pressure if applied during the
making of smears.
There are several vendors for the modified Romanowsky stain also commonly known as
Diff-Quikâ stain (we use Hema3, Fischer/CM Scientific, Morris Plains, NJ) which is what we prefer for
most of our lymph node smears. We also employ a modified Papanicolaou stain. Diff-Quik or any
Romanowsky based stain(toluidine blue, May-Grunwald-Giemsa, Wright-Giemsa, etc.) better highlights
cytoplasmic details of lymphoid cells, better accentuates the presence of lymphoglandular bodies (LGBs),
and displays cellular features that are more easily recognizable to hematopathologists because it is in
the same family of stains used in examining bone marrow aspirates and peripheral blood smears.
Papanicolaou stain highlights nuclear detail (chromatin, nucleoli, convolutions, nuclear knobs).
A 20 ml syringe attached to a syringe holder (Helmuth Industries, Linden, NJ) is employed,
and we use 23- or 25-gauge needles. Equal success has been demonstrated with smaller syringes and
syringe holders. Some individuals employ 22-gauge and 27-gauge needles as well. Details of the FNA
procedure are extensively illustrated and explained in an excellent monograph (Stanley, 1993). Every
needle pass is rinsed in a balanced salt solution after material is expelled onto slides. We use RPMI
-1640 cell culture media (Life Technologies, Grand Island, NY), but sterile normal saline can also be
used.
For lymphocyte immunophenotyping we use conventional flow cytometry (FCM) with 3-color analysis. A minimum number of cells required for FCM varies
because of instrumentation and even lymphoma type. Most agree that at least 1x106 cells are
required. Advantages of FCM are that cell preservation is better, a larger number of markers can be
employed, and FCM is superior in detecting small subpopulations of abnormal cells ("gating") in a
background of reactive lymphocytes. Some centers make cytospin smears and perform a panel of immunologic
markers (immunocytochemistry) on these so that morphology and immunology can be evaluated simultaneously.
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