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