Is cytology necessary in diagnosis of mediastinal mass?

Mediastinal mass is an uncommon abnormality found in clinical practices of respiratory physicians. The diagnosis of a mediastinal mass arises from a clinical suspicion, and more commonly, by a check-up chest x-ray. Definite diagnosis is necessary because the managements are different in various etiologies of the masses.

Adequacy of cellular sample recovered from small needle aspiration is the point of question among pathologist and physician in the diagnosis of mediastinal mass. Many centers recommend fine needle aspiration biopsy for cytology (FNAB) as an adequate procedure in this situation. This study is aimed to find the value of cytology and histological examination in the diagnosis of a mediastinal mass.

The study was done by prospective collected data of patients who were consulted for needle aspiration biopsies of their mediastinal mass since 1999 to 2006 at the Respiratory Diagnostic Unit, Division of Respiratory disease and Tuberculosis, Faculty of Medicine Siriraj Hospital. The protocol in evaluating mediastinal mass was to obtain both cytologic slides and tissue for histology from lesions in the mediastinum by ultrasonic guidance when they were possible.

During 1999 to 2006, there were 35 patients who had mediastinal masses referred for needle aspiration procedures. Their mean age and standard deviation were 42.37 +/- 16.97 year-old. Among these patients, 22 were men and 13 were women. The mean age (+/- standard deviation) of male patients was 40.47 +/- 17.17 years and 45.5 +/- 16.79 year-old for the female. The histology could make diagnosis in a significantly higher number of patients as compared to cytology (88.57% compared to 40%). There was statistically different higher diagnostic rate of UG-CNB than UG-FNA in non-carcinomatous group. The complications were mild.

Since most lung mass are carcinomatous in origin, depending on various factors (age, sex, smoking habit and size), the recommendation of FNA as the first line investigation are warranted because of high yield to risk for complication ratio, but in mediastinal mass in which many etiologic cells of origin cannot be diagnosed accurately by retrieved cytological cell, the CNB for small histology section is recommended as an initial investigation method without the loss of time required for cytological aspiration.