Case 1. Slide 1 History: 65 year old male presents with bilateral pleural effusions, a 40 pack year smoking history and peripheral and hilar lung masses. Specimen shown is from a tap of the pleural effusion.
Case 1. Slide 2. Pleural effusion specimen
What is your Diagnosis?
Diagnosis: Squamous Cell Carcinoma
The Diagnosis of Squamous Cell Carcinoma in Effusion Specimens David C. Wilbur, M.D., The Genesee Hospital, Rochester, New York The illustrations in this presentation represent material collected by the author as well as submitted material from the College of American Pathologists Non- Gynecologic Cytopathology Program. The presentation of squamous cell carcinoma (SCC) in effusions specimens is relatively infrequent when compared to the far more common involvement of the serous-lined body cavities by adenocarcinomas. Far and away, the most common primary sites for squamous tumors found in effusions are from the lung, the female genital tract, and the larynx. The diagnosis of squamous cell carcinoma in an effusion specimen may be difficult because the typical presentation of SCC seen in traumatic samplings such as FNA s, brushings, or scrapings is often different from that which may be noted in cells suspended in a fluid medium.
The cytologic features of SCC in traumatic samplings*: 1) Cells present predominantly in large groups and small tissue fragments - two dimensional (flat) sheets - well-defined cellular boundaries - no proliferation spheres 2) Isolated cells show keratinized pleomorphic cytoplasm 3) Associated inflammation and necrotic material is common 4) Dense opaque hyperchromatic nuclei * FNA s, brushings, etc. - see illustration A
The cytologic features of SCC in effusions*: 1) Cell groupings are more three dimensional (clusters) - cell boundaries become less distinct - non-keratinizing cells may form proliferation spheres - keratinizing cells will not form proliferation spheres 2) Isolated cells may be pleomorphic, but will tend to round up. - small cells with high N:C ratios may be more evident - cells still show dense, often glassy, cytoplasm 3) Cells may be vacuolated, giving a false appearance of adenocarcinoma *see illustrations B-G
The cytologic features of SCC in effusions (continued): 4) Anucleate squames and/or squames with degenerating pyknotic nuclei may be the only diagnostic feature 5) Keratin pearl formations may be seen rarely
The Physics of Effusions: Cells suspended in fluid media often may appear very different than the same tumors in traumatically sampled specimens. LaPlace s Law states that pliable objects suspended in a fluid medium will take on the shape which corresponds to the lowest energy level possible. The shape of lowest energy is that of a sphere. Therefore, cells with pliable membrane structures and internal organelles will, upon floating freely in the effusion specimen, tend to reorient themselves into rounded or spheroid shapes.
The Physics of Effusions (continued): The same physical phenomenon is also true for two dimensional groups of cells. Such aggregates will tend to ball-up in fluid suspension. These clusters, when mitotically active are referred to as proliferation spheres. Both of these factors affect the most significant changes in cells and cell groupings which are farthest from spherical or 3-dimensional shapes when tissue bound. Such is the case with squamous cell carcinoma, which may frequently consist of pleomorphic individual cells or 2 dimensional sheets of cells.
Illustration A: Keratinizing squamous cell carcinoma in FNA Note the prominence of pleomorphic forms.
Illustration B: Squamous cell carcinoma in effusion Note the rounded up pleomorphic cell.
Illustration C - Squamous cell carcinoma in effusion. Note the dense squamoid cytoplasm in the pleomorphic cells
Illustration D: Squamous cell carcinoma in effusion Note the many pyknotic and degenerated cells.
Illustration E - Squamous cell carcinoma in effusion. Note the proliferation ball composed of non-keratinizing elements.
Illustration F: Squamous cell carcinoma in effusion Note the pyknotic and residual pleomorphic cells.
Illustration G: Squamous cell carcinoma in effusion. Note the pyknotic cells among the residual pleomorphic forms present.
Other sources of anucleate squamous cells In effusions: 1) rupture of malignant or benign teratoma 2) fistula from alimentary or respiratory tracts 3) fragments of skin carried from the procedure 4) mesothelial mimickers - changes associated with radiation therapy
Differential diagnosis: 1) Sarcomas with pleomorphic cells Pleomorphic sarcoma cells presenting in fluids will also likely show changes to a spherical conformation. The presence of only isolated cells with virtually no cell groupings should raise sarcoma as a diagnostic possibility. The use of immunohistochemistry is useful in making this differential distinction. (see illustrations H&I) 2) Rheumatoid effusion Pleomorphic cell fragments containing either pyknotic or no nuclei are seen in this type of inflammatory effusion. These cell fragments can easily be mistaken for anucleate or atypical squames. The presence of multinucleate giant cells, and a granular background (as well as the clinical history) should be helpful in establishing a correct diagnosis. (see illustration J)
Differential diagnosis (continued): 3) Adenocarcinoma In cases of non-keratinizing squamous cell carcinoma, vacuolizations (degenerative) can be noted in the cytoplasm. Use of mucin stains can be of assistance in distinguishing these two processes. (see illustration K & L) 4) Reactive mesothelium Occasionally, reactive mesothelium can present in proliferation balls and show cytoplasm with a very dense cytoplasm with ectoplasmic ringing. The appearance of a dimorphic population of cells is more characteristic of malignancy while a monomorphic population of such cells is usually indicative of a benign reactive mesothelial process. (see illustration M)
Illustration H - Rhabdomyosarcoma cells in effusion. Note the rounding up of these normally spindled cells.
Illustration I - Rhabdomyosarcoma cells in effusion with immunocytochemical stain for desmin (cell block)
Illustration J - Rheumatoid effusion - filter preparation. (case courtesy of Kim Geisinger, M.D., Bowman-Gray)
Illustration K - Gastric adenocarcinoma with numerous vacuoles stained for mucin (cell block of effusion)
Illustration L - Negative mucin stain(on cell block) of reactive mesothelium with vacuoles to compare to Illustration J.
Illustration M - Benign reactive mesothelial cells showing proliferation balls and a monomorphic population
Summary: Squamous cell carcinoma is an uncommon tumor to present in effusion specimens. But when it is present it can present some unique problems for interpretation. These problems relate to conformational changes which occur in pleomorphic cells suspended in a fluid medium and to the unique features of squamous cancers themselves. Non-keratinized cells are most commonly seen and these can closely mimic adenocarcinoma, particularly due to cytoplasmic vacuolization, as well as the three-dimensionality of cell groupings. A variety of nonsquamous processes have been described which can also give rise to cells in an effusion which may mimic pleomorphic or keratinized squamous cancer cells. Close attention to cellular details as described, as well to a thorough clinical evaluation with history and physical will greatly aid in coming to a correct diagnosis.
References: 1) Smith-Purslow MJ, Kini SR, Naylor B. Cells of squamous cell carcinoma in pleural, peritoneal, and pericardial fluids. Origin and morphology. Acta Cytol 1989;33:245-253. 2) Tao L-C. Cytopathology of Malignant Effusions. ASCP Press, Chicago, 1996, pp.76-77. 3) Demay RM. The Art and Science of Cytopathology, Volume 1. ASCP Press, Chicago, 1996, p. 274.