Abstract
Cancer of unknown primary site is a histologically confirmed cancer that manifests in advanced stage, with no identifiable primary site following standard diagnostic procedures. Patients are initially categorized based on the findings of the initial biopsy: adenocarcinoma, squamous-cell carcinoma, neuroendocrine carcinoma, and poorly differentiated carcinoma. Appropriate patient management requires understanding several clinical and pathological features that aid in identifying several subsets of patients with more responsive tumors.
Highlights
IntroductionCancer of unknown primary site (CUP) is defined as a group of metastatic tumors for which a standardized diagnostic work-up fails to identify the site of origin at the time of diagnosis
PrognosisCancer of unknown primary site (CUP) is defined as a group of metastatic tumors for which a standardized diagnostic work-up fails to identify the site of origin at the time of diagnosis.Currently, CUP accounts for 3–5% of all tumors and is among the 10 most frequent tumors in developed countries
The 20% of CUPs that respond better to therapy and have better prognosis include: men with poorly differentiated carcinoma with midline nodal distribution, squamouscell carcinoma involving the head and neck lymph nodes, women with papillary adenocarcinoma of the peritoneal cavity or adenocarcinoma affecting only axillary lymph nodes, men with blastic bone metastases and high PSA, neuroendocrine carcinomas of unknown primary site, adenocarcinoma with a colon-cancer profile (CK20?, CK7, CDX2?), isolated inguinal nodes, and patients with one small, potentially resectable tumor
Summary
Cancer of unknown primary site (CUP) is defined as a group of metastatic tumors for which a standardized diagnostic work-up fails to identify the site of origin at the time of diagnosis. The 20% of CUPs that respond better to therapy and have better prognosis include: men with poorly differentiated carcinoma with midline nodal distribution, squamouscell carcinoma involving the head and neck lymph nodes, women with papillary adenocarcinoma of the peritoneal cavity or adenocarcinoma affecting only axillary lymph nodes, men with blastic bone metastases and high PSA, neuroendocrine carcinomas of unknown primary site, adenocarcinoma with a colon-cancer profile (CK20?, CK7-, CDX2?), isolated inguinal nodes (squamous carcinoma), and patients with one small, potentially resectable tumor. IHC testing is cost-effective and should be carried out initially in all CUPs. IHC can provide information about three aspects: the tumor lineage (carcinoma, melanoma, lymphoma, or sarcoma); tumor subtype (adenocarcinoma, germ-cell, hepatocellular, renal, thyroid, neuroendocrine, or squamous-cell cancer), and the primary site of adenocarcinoma (Fig. 1). Empirical adjuvant chemotherapy is reasonable in this setting, in patients with poorly differentiated carcinoma [24]
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