Metastasis of unknown origin (MUO) manifests either as a tumor deposit
in an organ, often cervical lymphadenopathy, or as a multiorgan carci
nomatosis. As a diagnostic and therapeutic challenge, the definition o
f its cell type and possibly its origin is imperative, although a limi
ted diagnostic investigation is usually recommended. At Hines VA Hospi
tal, from 1986 to 1994, there were 116 cases with admitting clinical d
iagnosis of MUO, evaluated by fine-needle aspiration cytology (FNAC).
The ages of patients ranges from 29 to 82 years (mean 56 years). All w
ere male; Caucasians predominated. The FNAC examination with Diff-Quik
and Papanicolaou smears were complemented with special and immunostai
ns in 48 cases (41%) and electron microscopy in 93 cases (80%). The FN
AC involved lymph nodes in 57 cases (49%), liver in 27 cases (23%), sk
in in 22 cases (19%), bone in six cases (5%), lung in three cases (3%)
, and pleura in one case (1%). The neoplasm was generally cell typed,
and there were 60 adenocarcinomas/poorly differentiated carcinomas, 26
small-cell carcinomas (SCC), 23 squamous-cell carcinomas (SQCC), and
six undifferentiated large-cell carcinomas. The primary source was def
ined in 30 cases (26%), consisting of lung in 11 cases, prostate in ni
ne, kidney in four, colon in four, pleura in one, and peritoneum in on
e. Clinical correlation also supported a lung origin for the SCC, whil
e the majority of the SQCC in upper and middle cervical lymph nodes we
re considered head-and-neck tumors. Our results affirm that FNAC is a
viable and simple procedure in MUO investigations. (C) 1998 Wiley-Liss
, Inc.