mgh:cyto-week1-6

Body Cavity Fluids Cases: Ivan Chebib MD, Amy Ly MD, Ron Arpin SCT

Basic cytomorphology: Normal mesothelial cells – MN05-G13557

Sheets of benign mesothelial cells are often smaller than 12 cells, but may sometimes be composed of upwards of 50 cells
In these photomicrographs, the even dispersal of uniform cells, with regular nuclei, delicate nuclear membranes and small round nucleoli signal the benign nature of these cells

Reactive mesothelial cells – N13-8012

Under conditions of an inflammatory process, mesothelial cells are increased in number, can exhibit a wide range of sizes, and may be multinucleated
The keys to diagnosis involve (1) applying individual criteria of benignity and (2) establishing the presence of an uninterrupted continuum of sizes from small to very large
Note enlarged nuclei, small multiple nucleoli, and spaces between adjacent cells, so called "windows"
Inflammatory cells are present in the background
Like pleural effusion, mesothelial cells in peritoneal effusions may exhibit a range of cell sizes
Mesothelial cells may be admixed with inflammatory cells and histiocytes.

Mesothelioma – N12-12597

The key to diagnosing mesothelioma is not identifying a second malignant cell population
Final determination may require immunocytochemistry or a cell block with immunohistochemistry, electron microscopy, or other specialized techniques
Individual malignant mesothelial cells exhibit a rim of ruffled, less dense cytoplasm (ectoplasm), surrounding dense cytoplasm around the nucleus (endoplasm)
Tumor cells may be seen in a background of blood and proteinaceous debris
Groups of more than 12 cells may be a feature of malignancy.
High N/C ratio with variability in nuclear size and occasional multi-nucleation confirm the malignant nature of these cells
Differential diagnoses include adenocarcinoma and mesothelioma
Fine microscopic features of peripheral cell membranes and intercellular windows may suggest mesothelioma
Abnormal mitotic figures may be noted with mesothelioma, other malignancies, as well as occasional reactive mesothelial cells in effusions

Metastatic adenocarcinoma – lung – N13-7980

Metastatic adenocarcinoma – breast – C99-T533

Metastatic ductal carcinoma cells exhibits large irregular nuclei and nucleoli
The classic description of metastatic breast cancer in pleural effusions employs the term "cannonballs" to emphasize the rounded arrangement of tumor cells
They may have a relatively small nuclear size
Nuclei are vesicular with prominent nucleoli
Cytoplasmic vacuoles are uncommon
A cell block of the cells allows for assay of hormonal receptors or other epithelial markers, such as her-2-neu

Metastatic adenocarcinoma – ovary – N13-6042 and N13-5843

Cells of papillary serous ovarian adenocarcinoma in a pleural effusion represent a discontinuous population of cells
Their cell and nuclear size is variable
Increased nuclear to cytoplasmic ratio and cytoplasmic vacuoles are features
Cells may exist singly or in small acinar groups
Vigorous peritoneal washes may dislodge microscopic tumor
Washes are an integral part of staging laparoscopy
Because of the washing procedure, tumor cells generally come off in three- dimensional cohesive groups and may be admixed with sheets of benign mesothelium
The tumor cells are easily distinguished by size, malignant characteristics and crowded configurations

Metastatic adenocarcinoma – GI –C98-N39001

Gastric adenocarcinoma
Cells with malignant features are present as a distinct population
Some may exhibit nuclear displacement by a large secretory vacuole, a "signet ring" cell
Origin from one part of the GI tract over another cannot be easily ascertained
Cholangiocarcinoma, either from an intra-hepatic source or from an extra-hepatic biliary tree, may look like adenocarcinoma from elsewhere in the GI tract
By exclusion of other sources through endoscopy, ultrasonography and/orCT imaging, the location may be determined.

Melanoma –C99-W27742

Lymphoma – N13-6082