Clinically evident metastatic lymph nodes are generally characterized by diffuse
involvement; hence, FNC is diagnostic in most cases;when the primary tumour is
unknown, FNC may contribute to its identification. As in case of lymphomas, the
immediate evaluation of the smear may require additional passes, can orientate the
management of the diagnostic material and lay out an immunocytochemical panel
combining cytological features and clinical data. If the primary tumour is known, FNC
may produce a definite diagnosis using routine smears. Differentiated metastatic
tumours show, in most of the cases, quite indicative cytological features: papillary
thyroid carcinoma, melanoma or breast carcinoma may be typical enough to suggest
their histogenesis at FNC. Even some poorly differentiated tumours, such as
undifferentiated pharynx tumours or lung carcinoma, for their peculiar cytological
features are often typical enough to suggest the primary tumor.
Metastases from unknown tumours are approached in different ways in different
districts. In cases of breast tumours, pre-surgical FNC assessment of axillary lymph
nodes has become less significant since they are surgically investigated during
surgery. Conversely FNC of clinically evident axillary lymph nodes may reveal
metastases of unknown and sometimes undetectable breast tumours. Papillary
thyroid carcinoma may cause precocious lymph nodal metastases; thyroglobulin
measurement in FNC wash-out, combined with traditional smears may be useful to
diagnose lymph node metastases of papillary thyroid cancer. Tyrosinase reversetranscriptase
polymerase chain reaction of aspirates obtained by ultrasound-guided
FNC of sentinel nodes has been utilized in patients with melanoma to detect occult
metastases, with different degrees of diagnostic accuracy.
In most cases, a basic immunocytochemical panel combining two or more antibodies
may suggest the primary tumour (see tables I and II). In this perspective both
cytospins and cell blocks generally produce a sufficient number of slides, and cell
blocks allow the testing of different antibodies on the same cell groups.
Table I: basic antibodies for tumours identification
Table II: cytokeratins expression in epithelial tumours
Squamous cell carcinoma
Lymph-nodal metastasis from squamous cell carcinoma may show variable cytological
presentations; thick groups of poorly differentiated cells, differentiated squamous malignant cells,
“tadpole” cells and abortive corn pearls may be intermingled with lymphoid cells or in a necrotic
background.
Squamous cell carcinoma
Lymph-nodal metastasis from squamous cell carcinoma showing groups or isolated squamous
cells with atypical nuclei and different degree of differentiation. In some cases a necrotic or
suppurative background may simulate an inflamatory process.
Lung adenocarcinoma
Groups of epithelial cells organized in balls or dense groups with scattered lymphoid cells
in the background.
Undifferentiated rinopharinx carcinoma
Rinopharinx, carcinoma may cause precocious lymph-nodal metastases; in most of the cases
later cervical lymphnodal metastases are the first sign of the disease. Small groups of poorly
differentiated cells or isolated undifferentiated cells, cytokeratin positive, represents the typical
presentation of lymph nodal involvement.
Renal carcinoma
Lymph nodal metastases from renal carcinoma may be suggested by large, isolated cells with
wide clear and or vacuolated cytoplasm or by large groups of cells with “oncocytic” large
cytoplasm and bland nuclei.
Melanoma
Dispersed cell population of cells with large vacuolated cytoplasm and evident nucleoli. Note
cytoplasmic nuclear inclusion. Cells in a cell block are S100 positive.
Melanoma
Isolated melanoma cells, intermingled with lymphocytes. Cells show dense large vacuolated
cytoplasm, eccentrical atypical nuclei and evident nucleoli and are HMB45 positive.
Papillary thyroid carcinoma
Papillary thyroid carcinoma may give precocious metastases to cervical lymph nodes.
Metastases may be massive, focal or even cystic. Sometimes only few small groups of
follicular cell are present; thyroglobulin immmunostain may confirm their thyrodal origin.
Mesothelioma
Infrequently mesothelioma may determine lymph-nodal metastases. Mesothelial cells show
typical intercellular “windows”, positivity for cytokeratin, vimentin and calretinin and
negativity for LCA with positive lymphocytes in the background.
Ovary
Lymph nodal metastasis from ovary carcinoma showing thick, papillary epithelial structures
and lymphoid cells in the background. Epithelial groups are CA125 positive.
Bladder carcinoma
FNA of inguinal lymph node of a patient suffering from recidivant urinary bladder papillomas.
Smears show an epithelial tumour, CK7 and CK20 positivity is consistent with an urothelial
primary tumour.
Disgerminoma (seminoma)
Dispersed, poorly differentiated large cells with evident nucleoli and fragile cytoplasm. The back
ground is usually “dirty” with scattered lymphocytes intermingled. Cells are α-Fetoprotein
positive.
Breast carcinoma
Lymph nodal metastasis from breast carcinoma showing groups of ductal cells in a
haematic background or intermingled with lymphocytes. Estrogens immunostain may
be helpful to reveal the mammary origin.