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CYTOLOGY SECTION - ORIGINAL ARTICLE |
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| Year : 2008 | Volume
: 51
| Issue : 1 | Page : 88-90 |
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| Fine needle aspiration cytology of anterior mediastinal masses |
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Fanny Desai1, Manoj Shah2, Shreedevi Patel3, Shilin N Shukla4
1 Shija hospitals and Research Institute, Imphal, Manipur, India
2 Department of Pathology, Gujarat Cancer and Research Institute, Gujarat, India
3 Department of Radiology, Gujarat Cancer and Research Institute, Gujarat, India
4 Department of Medical Oncology, Gujarat Cancer and Research Institute, Gujarat, India
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 Abstract | | |
Objective: The main aim of the study is to evaluate the computed tomography (CT)-guided fine needle aspiration cytology (FNAC) of anterior mediastinal mass as a diagnostic procedure. Materials and Methods: In all 135 cases, the material was obtained by CT-guided FNAC technique followed by staining with Papanicolaou and May-Grunwald-Giemsa stains. The histological material was obtained by needle biopsies, wedge biopsies and resection specimens. Immunohistochemical stains were used to confirm diagnosis in selected cases. Results: Among 135 cases, cytohistology correlation was found in 92 cases. Correct typing was done in 53.33% cases. No correlation was found in 14.81% cases. Material was unsatisfactory in 18.51% cases. The diagnostic accuracy and positive predictive values were 85.71% and 78.26%, respectively. Conclusion: Although there are some limitations, most lesions of the anterior mediastinum can be diagnosed on FNAC. Keywords: Anterior mediastinum, computed tomography, fine needle aspiration cytology
How to cite this article:
Desai F, Shah M, Patel S, Shukla SN. Fine needle aspiration cytology of anterior mediastinal masses. Indian J Pathol Microbiol 2008;51:88-90 |
| Introduction | |  |
The differentiation of anterior mediastinal lesions is of clinical importance because of major differences in their management. Fine needle aspiration cytology (FNAC) has a major role in diagnosis of anterior mediastinal masses (AMMs) because it is safe and easy to perform. Many authors have found that most malignant lesion can be diagnosed on FNAC and accurate tumor typing is often possible. [1],[2],[3],[4],[5],[6],[7],[8] In this study, we evaluate the FNAC as diagnostic procedure. We examined cytological features of different lesions with histological correlation and immunohistochemical confirmation in some. The reasons for discordant cytology and pitfalls of entities with differential diagnosis are also discussed.
| Materials and Methods | | |
A total of 135 cases of AMM were identified from January 1999 to November 2003. All FNACs of these AMMs were performed under guidance of Computed Tomography using 22-gauge lumbar puncture needle. Air-dried and wet-fixed [95% alcohol] smears were prepared and stained by May-Grunwald-Giemsa [MGG] and Papanicolaou stains, respectively. Histological material was obtained by needle biopsies, wedge biopsies and resection of the specimens. The tissues were fixed in 10% formalin, processed, embedded in paraffin and 4-micron thin sections were cut. The histological sections were stained by Hematoxylin and Eosin [H and E] stain. The immunohistochemical studies were carried out on cellblocks and biopsies by direct avidin-biotin-peroxidase method using various antibodies. The antibodies that were used included anti-cytokeratins, anti-epithelial membrane antigen, anti-leucocyte common antigen, anti-alpha-fetoprotein, anti-beta human gonadotropins, anti-neuron-specific antigen and anti-chromogranins.
The slides were reviewed with special attention to the cytological details of cases with incorrect typing. The cytological features evaluated are shown in [Table - 1]. For primary carcinomas, metastasis was ruled out by clinical history.
The reports that described the aspirated material as "hemorrhagic only," insufficient for diagnosis" and "scanty cellularity" were considered to be unsatisfactory. The reports stating "possibility of," "suggestive of," "consistent with" or "diagnostic of" with different wrong histological diagnosis were considered as incorrect typing. Similar statements with correlated histological diagnosis were considered as correct typing.
| Results | | |
Cytological smears of 135 cases of AMM and histological sections of these cases were studied. Correct typing was found in 72 cases, incorrect typing in 20 cases and smears were unsatisfactory in 25 cases. The histological diagnoses were not available in 18 cases. The diagnostic accuracy and positive predictive value for the presence of neoplasm are 85.71% and 78.26%, respectively. The summary of cases with discordant cytology along with reasons, unsatisfactory samples and histocytology correlation are given in [Table - 2],[Table - 3],[Table - 4] respectively.
| Discussion | | |
FNAC has a major role in the diagnosis of AMMs because it is safe and easy to perform. Many authors have found that most malignant lesions can be diagnosed on FNAC and accurate tumor typing is often possible. [1],[2],[3],[4],[5],[6],[7],[8] Power et al. , in his large study of 189 cases, found diagnostic accuracy and positive predictive value at 87% and 97% respectively. [5] We found diagnostic accuracy at 85.71% and positive predictive value at 78.26%. A total of 14.81% cases were misdiagnosed.
The common diagnostic differences between large cell lymphoma vs type B1, B2 thymomas (WHO classification; lymphocyte rich, cortical thymomas), Germ cell tumors (GCT) vs large cell lymphoma, carcinoid vs lymphoma, GCT vs thymic carcinoma, GCT vs metastatic poorly differentiated carcinoma, Hodgkin's disease vs inflammatory lesion, and lymphoma vs small cell carcinoma. Our findings are similar to those found by other authors. [9],[10],[11],[12] The common factors associated were low cellularity, associated hemorrhage, poor fixation and confusion with patterns [diffuse versus clustering], size of cells [small cells versus large cells] and rarity of lesions [such as thymic carcinoids]. In most cases, more than one factor was responsible: low cellularity caused hemorrhage-simulated discohesiveness. High cellularity with tissue micro-fragments and associated fibrosis caused false sense of clustering. In another case, forceful smear preparation along with drying artifact produced cellular distortion and smudging in lymphoma that lead to its wrong diagnosis as small cell carcinoma on FNAC. Poor spread by untrained person or because of clotting of blood along with the tissues produced false sense of clustering. When cellularity was found to be adequate without any technical fault, the cell size and patterns of different lesions were confused with each other. In spite of adequate cellularity, in one case, tissue sample did not represent the entire lesion. To avoid diagnostic errors on optimally prepared smears, one should have adequate knowledge and experience of site specific common lesions. We found that some of the errors in our cases occurred due to lack of experience. Lymphomas are characterized by hypercellular smears with diffuse discohesive pattern. The nuclei show irregular outline with nucleoli and scanty cytoplasm. Numerous lymphoglandular bodies are identified in the background on MGG-stained smears; no molding is present. Low-grade lymphomas show high nuclear-cytoplasmic ratio, irregular nuclear outline, no nucleoli and scanty cytoplasm. Lymphoblastic lymphomas show powdery chromatin with small single or multiple nucleoli and clefts in nuclei.
Neuroendocrine tumors of the mediastinum show small cells in loose clusters as well as single scattered cells. Nuclei are round to ovoid, mildly pleomorphic with stippled chromatin and small indistinct nucleoli; the cytoplasm is scanty. Our findings in these lesions are similar to those of Wang et al. and Nicholas et al. [13],[14] In addition, we found occasional mitosis and cells adherent to fibrovascular stromal fragments along with minimal nuclear molding. The characteristic nuclear features with absence of prominent nuclear molding, smearing artifact and cellular pattern can usually distinguish it from SCC and lymphomas. [13],[14],[15],[16] In type B3 thymomas (epithelial thymomas), cells are larger with vesicular nuclei and distinct nucleolus with moderate amount of cytoplasm in the lymphocytic background (absent in carcinoid tumors). [17],[18]
It is difficult to differentiate GCTs from poorly differentiated carcinomas. Serum markers, clinical history and immunochemistry are required for confirmation. [19],[20] Benign lesions usually are diagnosed correctly; however, because of scanty cellularity and hemorrhage in some cases, multiple FNACs are required to diagnose them.
Thus, our study shows that when technical conditions are controlled, most of the time, the accurate diagnosis of the AMM is possible by CT-guided fine needle aspiration cytology, which is a safe and easy procedure to masses within the complex anatomy of the anterior mediastinum.
| Conclusion | | |
Computed-tomography-guided FNAC can diagnose most of the lesions of anterior mediastinal masses on optimally prepared smears.
| References | | |
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Correspondence Address:
Fanny Desai
Shija Hospitals and Research Institute, Langol, Imphal, Manipur - 795 004
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/0377-4929.40413
[Table - 1], [Table - 2], [Table - 3], [Table - 4] |
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