Immunohistochemistry at rescue in the cancers of unknown primary origin

Aims: To identify and explore the role of immune histochemical markers in the diagnosis of malignancies of unknown primary origin.Background: Cancer of unknown primary (CUP) origin is a heterogenous group of cancers explained by the presence of metastatic disease with no identified primary tumor at presentation. These malignant neoplasms with unknown primary origin can be identified and classified by the use of a robust IHC panel which may permit development of tailored treatment algorithm with specific targeted agents. Methods: In the current study, Histopathology and biopsy samples from 38 patients were included which were diagnosed as CUP and referred to IHC department, M. P. Shah medical college and hospital, Jamnagar from 2019 to 2023. CUP were diagnosed and classified of their histologic types on basis of hematoxylin and IHC slides. Results: From 2019 to 2023, out of 4026 cases, CUP constitutes 0.99% (~1%). The age group (60-69) years have the highest cases 14/40 cases with equal distribution in both sexes. Lymph node represents (42.5%) which is the most common presenting site followed by liver (12.5%) and lung (10%). In 50% of the cases, the primary site was determined; whereas 37.5% cases were remained unknown for primary and 12.5% cases were given an only differential diagnosis. Adenocarcinoma (66.6%) was the most common subtype, followed by squamous cell carcinoma (13.15%), undifferentiated neoplasm (10.52%). Conclusions: The most common presenting sites were lymph nodes, liver, lungs and others. CUP cases are uncommon (0.88%) and primary origin of these CUPs were identified in 50% cases. Sub typing of primary site were adenocarcinoma, squamous cell carcinoma and carcinoma with undifferentiated neoplasm.