Cytological features of melanoma in exfoliative fluid specimens.
OBJECTIVE
To describe the cytological appearances of melanoma in fluid specimens and potential diagnostic pitfalls in interpreting such specimens, which have been infrequently reported in the literature.


METHODS
Cases of melanoma diagnosed at a single institution between 1993 and 2008 in cytology specimens of fluids (pleural, ascitic, cerebrospinal and other fluids), but excluding fine needle biopsy specimens, were identified and reviewed.


RESULTS
32 fluid specimens containing metastatic melanoma (from 26 patients) were identified. Most of the specimens were moderately cellular and showed moderate to marked nuclear pleomorphism. Mitotic figures and intranuclear cytoplasmic invaginations were identified in 11 (34.4%) and seven (21.9%) cases, respectively. Melanin pigment was seen in eight (25.0%) cases. Variable numbers of histiocytes were present, and mesothelial cells were present in body cavity fluid specimens.


CONCLUSIONS
In fluid specimens, reactive mesothelial cells and histiocytes may mimic epithelioid melanoma cells. Awareness of the morphological features and diagnostic pitfalls of melanoma in fluids is necessary to avoid the potentially serious consequences of misdiagnosis.
Murali
R
R
Department of Anatomical Pathology, Royal Prince Alfred Hospital, New South Wales, Australia. rajmohan.murali@email.cs.nsw.gov.au
Loughman
N T
NT
McKenzie
P R
PR
Watson
G F
GF
Thompson
J F
JF
Scolyer
R A
RA
D000230:Adenocarcinoma / Q000175:diagnosis; D000368:Aged; D000369:Aged, 80 and over; D001826:Body Fluids / Q000166:cytology*; D003581:Cytodiagnosis; D003937:Diagnosis, Differential; D003951:Diagnostic Errors; D004847:Epithelial Cells / Q000473:pathology; D005260:Female; D006644:Histiocytes / Q000473:pathology; D006801:Humans; D008297:Male; D008545:Melanoma / Q000175:diagnosis / Q000473:pathology* / Q000556:secondary*; D008875:Middle Aged; D012680:Sensitivity and Specificity; D012878:Skin Neoplasms / Q000473:pathology*