Carcinoma of Unknown Primary Diagnosis

Carcinoma of unknown primary accounts for two to five percent of new cancer diagnoses and presents with metastatic disease in lymph nodes, liver, lung, bone, or peritoneum without identifiable primary tumor on imaging, endoscopy, and clinical examination. Adenocarcinoma is the most common subtype followed by squamous, neuroendocrine, and undifferentiated carcinoma.

Workup includes contrast computed tomography of chest abdomen pelvis, mammography in women, prostate specific antigen in men, gastrointestinal endoscopy when symptoms suggest, and tumor specific markers including alpha fetoprotein, beta human chorionic gonadotropin, and tissue immunohistochemistry panel. Molecular profiling and gene expression assays may suggest tissue of origin in selected cases.

Favorable subsets such as women with isolated axillary node adenocarcinoma resembling breast cancer, midline poorly differentiated carcinoma resembling germ cell tumor, peritoneal serous papillary carcinoma in women, and squamous cervical node disease receive site specific therapy with comparable outcomes to known primary cancers. Unfavorable group receives empirical platinum based combinations or experimental immunotherapy.