You answered: Epithelioid hemangioendothelioma
Sorry, that is INCORRECT
The correct diagnosis is: Epithelioid Mesothelioma
- Malignant cells look like mesothelial cells (no foreign or distinct second population of cells), cytologically ranging from benign-appearing to frankly malignant
- Important clue at low power - "more and bigger cells in more and bigger clusters" (aggregates containing 30-200 or more cells are characteristic)
- Cell clusters are highly irregular, knobby, with flower-like or papillary outlines, and are three-dimensional, with numerous "cell-in-cell" or "cell-embracing" patterns
- Individual cells are usually larger and more variable than benign mesothelial cells; giant multinucleated forms are often seen. Cells, however, maintain a relatively constant N/C ratio, which imparts a certain degree of uniformity, and resemblance to benign mesothelial cells (kinship). Spindle cells may be seen
- Peripheral cytoplasmic blebs and microvilli (lacy skirts) are accentuated in malignant mesothelial cells. Cytoplasmic vacuolation may also be seen
- Nuclei are centrally or paracentrally located, with enlarged, multiple, irregular nucleoli
- Macronucleoli are associated with malignancy. Mitotic figures are NOT helpful unless they are atypical, which are rarely seen
- Malignant mesothelioma is a tumour related to asbestos exposure
- It arises most commonly in the pleura, less commonly in peritoneum (tumours in pericardium or tunica vaginalis of the testis are rare)
- Cells grow as multiple plaques that coalesce into larger nodules visible radiographically as a pleural thickening
- Classified as:
epithelioid (most common; shows tubular, papillary, microcystic +/- patterns);
mixed (biphasic) types
- The majority of patients present with an effusion, usually unilateral, that is characteristically viscous to gelatinous (like synovial fluid, or honey) due to elevated levels of hyaluronic acid
- There are several diagnostic challenges:
- Hard to distinguish from reactive mesothelial cells.
Reactive mesothelial cells are usually less abundant, form smaller, less complex groups or flat sheets. Nuclei are more monomorphic, and may contain small nucleoli.
Mesothelioma cells are usually extremely abundant, and form large, irregular, complex three-dimensional aggregates. Nuclei are pleomorphic, with multiple or macronucleoli.
Flow cytometry (to measure DNA content) and cytogenetics may be used to aid distinction. Mesotheliomas show clonal cytogenetic aberrations (deletions of 1p, 3p, 22q most common) - detected by fluorescence-in-situ hybridization (FISH) on liquid-based preparations
- Hard to distinguish from metastatic adenocarcinoma, particularly when cells have vacuolated cytoplasm.
Adenocarcinoma has two distinct cell populations; PAS-D positive, negative for calretinin, CK5/6, WT1 (with exception of ovarian), positive for CEA, Leu-M1, B72.3, BER-EP4, TTF-1 (if from lung). Microvilli show small length:diameter ratio on electron microscopy.
Mesothelioma has a morphologic continuum with benign-appearing mesothelial cells; PAS-D negative, positive for calretinin, CK5/6, WT1 (with exception of ovarian), negative for CEA, Leu-M1, B72.3, BER-EP4, TTF-1. Microvilli show length:diameter ratio of 15:1 or greater on electron microscopy
- Epithelioid hemangioendothelioma is a good mimic of mesotheliomas (aggregates with round, centrally placed nuclei, abundant cytoplasm); positive for vascular markers CD34 and CD31, negative for calretinin and WT1
BACK TO IMAGES
DeMay RM. The Art & Science of Cytopathology. Chicago: ASCP Press, 1996; 278-85.
Cibas ES. Cytology: Diagnostic Principles and Clinical Correlates, Second Edition. Saunders, 2003; 126-30.