Fine-needle aspiration of lymph nodes in patients with acute infectious mononucleosis

Pitfalls in Lymph Node Fine Needle Aspiration Cytology

BACKGROUND

Fine needle aspiration cytology (FNAC) is an accurate, minimally invasive, and cost-effective biopsy method for enlarged lymph nodes. While the role of lymph node FNAC in the diagnosis of infectious or reactive conditions and metastatic malignancy is unquestioned, differing views still exist on its role in the diagnosis of lymphoma. Nevertheless, regardless of the practice setting, pitfalls and potential for error exist, and it is incumbent upon the pathologist to be aware of these pitfalls, as this is the first line of defence against errors.

SUMMARY

This discussion will focus on potential interpretational errors, specifically highlighting scenarios leading to false-negative and false-positive diagnosis and errors in tumour classification, with an emphasis on cytomorphology. Potential entities that may fly below the radar of the pathologist - so-called off-radar entities - are also discussed, as a reminder to consider broad differentials in cases with unusual morphologic features. Some reasons for false-negative diagnoses include low-grade lymphomas that mimic a mixed, polymorphous reactive lymphoid population or aspirates with a paucity of lesional cells, through either sampling error or the intrinsic nature of the entity, e.g., nodular lymphocyte predominant Hodgkin lymphoma. Some of the potential causes of false-positive diagnoses that are discussed include viral-associated lymphadenopathy, Kikuchi-Fujimoto lymphadenitis, or benign adnexal lesions mimicking metastatic malignancy. Errors in tumour classification covered include metastatic carcinoma, sarcoma, melanoma, and lymphoma mimicking each other, and Hodgkin lymphoma and its mimics. Finally, less common entities such as follicular dendritic cell sarcoma and others are briefly mentioned, to remind us of conditions that may slip under our diagnostic radar.

KEY MESSAGES

A systematic review of diagnostic pitfalls and traps is elucidated here, with some tips to avoid these traps. The triple approach to the diagnostic workup is emphasised, which includes rigorous clinicopathologic correlation, attention to cytomorphology, and judicious application of ancillary tests.

Fine needle cytology features of an atypical presentation of infectious mononucleosis

Infectious mononucleosis (IM) is a very common disease, and although in most instances, the patient develops an asymptomatic infection, other patients progress into an array of signs and symptoms that tend to be characteristic of the pathological process, guiding the clinician into choosing the right laboratory examinations under the suspicion of this illness. The most common symptoms are pharyngitis, lymphadenopathies and pyrexia, and the probabilities to develop this mononucleosis triad become greater with age. In other instances, IM can be a challenging disease to diagnose, mainly because the patient debuts with unusual symptoms such as nausea, skin eruptions, diarrhea and epigastric discomfort. The aim of the present article is to report the case of a 21-year-old female with a reactivation of IM, developing only multiple, asymptomatic lymph node enlargements in the head and neck region, showing no other sign or symptom.

Atypical lymphocytosis resembling non-Hodgkin’s lymphoma in peritoneal effusion of infectious mononucleosis: a case report

Peritoneal effusion appears to be an unusual complication of infectious mononucleosis (IM). The cytological features of peritoneal effusion from a patient affected by IM are presented. The patient was a 21-year-old Japanese woman, with typical and physical findings of IM. Ascites disappeared with resolution of acute IM. The cytospin smears of the ascitic fluid were highly cellular, consisting exclusively of lymphoid cells. Lymphoid cells were composed of large cells with broad basophilic cytoplasm, as well as of small to medium-sized cells having scant cytoplasm and irregularly shaped nuclei. The overall cytomorphological pictures posed serious difficulties in differentiating this condition from those of peripheral T-cell lymphomas manifesting ascites. The majority of atypical lymphocytes, including large cells, expressed CD3 and CD8. The present case indicates that IM should be added to the list of lesions considered for the differential diagnosis of non-Hodgkin's lymphoma of the peritoneal fluid, particularly regarding young adults.