mgh:cyto-week1-6

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

• Indications for cytology examination
• Procuring the specimen
• Test platforms/specimen processing and triage
• Reporting and terminology

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

• Papillary glandular arrangements of the tumor cells
• Prominent nucleoli, vacuolization and mitotic figures
• Distinctions from other sources of adenocarcinoma may be impossible.

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

• Dyshesive single cells
• Malignant nuclear features, eccentric nuclei
• Range of patterns: small, spindle or epithelioid cells
• Nuclear size variation
• Nuclear pseudoinclusions with bi-, and multinucleation
• Intracytoplasmic dusty brown melanin pigment
• S-100, HMB-45, Melan-A positive (not always)

Lymphoma – N13-6082

• Dyshesive single cells
• Open granular chromatin
• Nucleoli based on nuclear membrane in some subtypes
• Nuclear membrane protrusions and irregularity
• Scant cytoplasm in some subtypes (high N/C ratios)
• Lymphoglandular bodies in background
• LCA positive, B or T cell lineage