Table 3.

Favourable cancers of unknown primary and specific therapy

Histology	Clinical subset	Further investigation	Therapy
Adenocarcinoma	Female + axillary lymphadenopathies	Breast MRI ER/PR/HER-2	= Breast cancera
	Female + peritoneal carcinomatosis	CA 12.5	= Ovarian cancerb
	Male with blastic bone M1 and raised PSA	PSA	= Prostate cancerc
	Clinical/pathological features consistent with a primary colorectal tumour	IHC: CK20 +/CK7- and CDX2+	= Colon cancerd
	Single M1 lesion	PET	Local therapy ± CT
Squamous cell	Cervical lymph nodes	Endoscopy/PET? Tonsillectomy	= Head and neck cancere
	Inguinal lymph nodes		LND ± RT ± CT
Undifferentiated	Young male, mediastinum and/or retroperitoneum	hCG, AFP	= Extragonadal germ cell cancerf
Neuroendocrine	Low or high grade	Octreotide scan	= Neuroendocrine tumour

AFP alpha-fetoprotein, CK cytokeratin, CT chemotherapy, ER oestrogen receptors, hCG human chorionic gonadotropin, IHC immunohistochemistry, LND lymph node dissection, M1 metastasis, MRI magnetic resonance imaging, PET positron emission tomography, PR progesterone receptors, PSA prostate-specific antigen, RT radiotherapy

^aBreast cancer: females with adenocarcinoma and axillary lymphadenopathy should be treated as if they had stage II breast cancer

^bOvarian cancer: females with peritoneal carcinomatosis should be treated as if they had stage III ovarian cancer, especially in the case of raised CA 12.5, known adenocarcinoma histology, and if gastrointestinal origin has been ruled out

^cProstate cancer: males with blastic bone metastases and raised serum prostate-specific antigen should be treated as if they had metastatic prostate cancer

^dColorectal cancer: patients whose clinical and pathological features are consistent with a primary colorectal tumour should be treated using the same protocols as for metastatic colorectal cancer, especially in the case of known adenocarcinoma histology and CK20+/CK7- or CDX2+ immunohistochemical staining

^eTumours of the head and neck, and anogenital tumours: in patients with squamous cell carcinoma involving the cervical or inguinal lymph nodes only, locoregional approaches based on chemotherapy/radiotherapy strategies are warranted

^fExtragonadal germ cell tumours: young males with poorly differentiated mediastinal or retroperitoneal tumours should be treated as if they had extragonadal germ cell tumours