Metastatic carcinoma with unknown primary – does immunohistochemistry help to detect origin?

Carcinoma of unknown primary is a common clinical problem. They are often the first symptom of systemic malignancy. Hence, immunohistochemistry (IHC) is of importance in evaluating the primary origin. The aim was to detect the primary site of metastatic carcinoma and evaluate the role of IHC in diagnosing the same. Cases of metastatic carcinoma of unknown primary to lymph node, bone and parietis were collected. After initial histopathological examination on haematoxylin and eosin stained section, panel of immunohistochemistry were applied in search of most possible primaries. Forty eight cases of metastatic carcinoma of unknown primary to lymph node, bone, soft tissue and parietis were taken. After routine histopathological examination total seventeen antibodies were used in immunohistochemical test to detect the most possible primary site. Out of 48 cases, lung was primary site in 16 cases, gastrointestinal and pancreatico biliary tract in 12 cases, breast in 4 cases, thyroid in 5 cases, ovary in 8 cases and kidney in 3 cases. Immunohistochemistry has utility in detecting the primary site expeditiously, and thereby guide management and predict prognosis in a given case.