Journal List > Korean J Cytopathol > v.19(2) > 1006538

Korean J Cytopathol. 2008 Sep;19(2):72-85. Korean.
Published online September 30, 2008.
Copyright © 2008 The Korean Society for Cytopathology
The Cytopathology of Body Cavity Fluid
Eun Kyung Hong, M.D.
Department of Pathology, National Cancer Center Hospital, Korea.
Received August 11, 2008; Accepted August 25, 2008.


Cytologic examination of the body cavity fluid is very important because the specimens represent a significant percentage of nongynecologic samples and this cytologic examination may be the first, best or only chance for making the diagnosis of an underlying malignancy. The purposes of body cavity fluid examination are to correctly identify cancer cells and if possible, to identify the tumor types and primary sites when presented with unknown primary tumor sites. The most important basic differential diagnosis is that of benign and reactive disease vs malignant disease. Reactive mesothelial cells are a consistent population in body cavity fluid, and these are the most versatile cells in the body. Due to the specific environment of the body cavity, the exfoliated reactive mesothelial cells may show significant morphologic overlap with the morphology of cancer cells. With a focus on the differential points between reactive mesothelial cells and metastatic adenocarcinoma cells, the practical diagnostic approaches, the diagnostic clues and the pitfalls to achieve a correct diagnosis are presented in this review.

Keywords: Body cavity fluid; Cytopathology; Mesothelial cell; Metastatic carcinoma


Fig. 1
Cytologic features of monolayered sheet of non-reactive mesothelial cells (A) and reactive mesothelial cells (B-D). Reactive mesothelial cells show abundant dense cytoplasm with frayed margin and vacuolation(B). Bi- or multinucleation(C) and proliferation sphere formation(D) are common.(Papanicolaou stain).
Click for larger image

Fig. 2
The smear patterns of malignant serous effusion. It may be monomorphic population(A) or dimorphic population(B). (Papanicolaou stain).
Click for larger image

Fig. 3
Diagnostic approaches when atypical cells are present in the body cavity fluid. Atypical cells equivocal for malignant cells(A) and atypical cells unequivocal for malignant cells(B).
Click for larger image

Fig. 4
Cytologic features of malignant mesothelioma. It shows highly cellular smear with numerous singly scattered cells and irregular cellular clusters in the smear(A). The clusters retain multiknobby appearance of mesothelial cells(B) and individual cancer cells show abundant dense endoplasm of mesothelial cell(C).(A-C; Papanicolaou stain). For confirmation of diagnosis, immunohistochemical stains can be applied in this cell block(D; H&E ).
Click for larger image

Fig. 5
Various intracytoplasmic materials, clues for histologic typing. These can be cytoplasmic kerain of squamous cell carcinoma(A), psammoma bodies in papillary tumor(B ; H&E ), cytoplasmic mucin of signet ring cell carcinoma(C) or cytoplasmic melanin of malignant melanoma(D).(A, C, D; Papanicolaou stain).
Click for larger image

Fig. 6
Commonly found cellular aggregates in the smear of body cavity fluid. Ball-like cellular aggregates without fibrovascular cores(proliferationsphere or cell ball(A and B)), papillary structure with fibrovascular core(C), or pseudopapillary structure by adhesion of more than two cell balls(D) can be seen.(Papanicolaou stain).
Click for larger image

Fig. 7
Diverse cellular patterns in the smear of body cavity fluid. Indian-file pattern shows single row or chain of cancer cells(A). Acinar arrangement of cancer cells shows central luminal structure(B). In pseudomyxoma peritonei, abundant mucinous materials can be smeared in the background(C). Not only hematolymphoid malignancy but poorly differentiated carcinoma can show predominantly scattered isolated cells due to poor cohesion(D).(Papanicolaou stain).
Click for larger image

Fig. 8
Atypical reactive mesothelial cells. Even in benign process, reactive mesothelial cells can have morphologic features quite similar to those of malignant cells, leading to false positive diagnosis.(Papanicolaou stain).
Click for larger image

Fig. 9
Immunohistochemical stains of the cell block preparations. Calretinin(A) and CK5(B) are frequently used mesothelial cell markers and MOC 31(C) is frequently used epithelial cell marker. Site specific markers, such as TTF-1(D), are very helpful to detect primary site of metastatic carcinoma. (Immunohistochemical stain).
Click for larger image


Table 1
Common primary sites of malignant serous effusions
Click for larger image

Table 2
Distinguishing cytologic features of reactive mesothelial cells, malignant mesothelioma and metastatic adenocarcinoma
Click for larger image

1. Shidham VB, Atkinson BF. In: Cytopathologic Diagnosis of Serous Fluids. Philadelphia: Saunders-Elsevier; 2007.
2. Motherby H, Nadjari B, Friegel P, Kohaus J, Ramp U, Bocking A. Diagnostic accuracy of effusion cytology. Diagn Cytopathol 1999;20:350–357.
3. Wilbur DC. In: Syllabus. College of American Pathologists; 2006. Body cavity fluid examination: Problem patterns and their resolution.
4. Churg A, Cagle PT, Roggli VL. In: Tumors of the serosal membranes. 2006. AFIP atlas of tumor pathology. 4th series, Fascicle 3
5. Pereira TC, Saad RS, Liu Y, Silverman JF. The diagnosis of malignancy in effusion cytology: A pattern recognition approach. Adv Anat Pathol 2006;13:174–184.
6. Moriaty AT, Stastny J, Volk EE, et al. Fluids-Good and Bad Actors. Observation from the College of American Pathologists interlaboratory comparison program in nongynecoloic cytology. Arch Pathol Lab Med 2004;128:513–518.
7. Cibas ES, Ducatman BS. In: Cytology. Diagnostic principles and clinical correlates. Philadelphia: Saunders-Elsevier; 2007. pp. 119-144.
8. Mohanty SK, Dey P. Serous effusions: diagnosis of malignancy beyond cytomorphology. An analytic review. Postgrad Med J 2003;79:569–574.
9. Choi S, Kang MS. The diagnostic utility of mesothelial markers in distinguishing between reactive mesothelial cell and adenocarcinoma cells in serous effusions with cytospin preparation. Korean J Cytopathol 2006;17:108–115.
10. Choi YD, Kim JH, Kim G, et al. Immunocytochemical panel for distinguishing between adenocarcinomas and reactive mesothelial cells in effusion cell blocks; The Proceedings of the 22th Annual Spring Meeting of the Korean Society for Cytopathology; 2008. pp. 39.