Cancer of Unknown Primary: A Review on Clinical Guidelines in the Development and Targeted Management of Patients with the Unknown Primary Site

Abstract

Cancer of unknown primary (CUP) is a malignant widespread metastatic disease without an identifiable primary site after extensive clinical investigation. Recently, a decline is observed in the diagnosis of CUP, mainly due to improvement in detection of the primary tumors, thus decreasing the unknown primaries. Worldwide, CUP is the sixth to eighth most common malignancy, accounting for 2.3% to 5% of a new cancer diagnosis. CUP is third to fourth most common cause of death due to cancer-related mortality. The prognosis of CUP is depressing with the median survival of three to six months in the previous studies, but according to recent studies, median survival is less than one year. High risk for developing CUP is seen in heavy smokers (26 or more cigarettes/day) and individuals with the lowest quartiles of waist circumference. A weak association is observed with the use of alcohol consumption and low level of education. Human papillomavirus DNA plays a role in those with squamous cell carcinoma of unknown primaries in head and neck regions. In the diagnosis of CUP, comprehensive medical history, complete physical examination (including genitourinary, rectal exam, and breast examination in women) and necessary laboratory tests are crucial.Whole-body positron emission tomography-computed tomography (PET/CT) is the investigation of choice to assess the entire body for CUP. Multiparametric 3T-MRI (MP-MRI) is used to examine the local soft tissue status, helps in the staging of the tumor, and to determine the extent of involvement of tissue for medical as well as prognostic purposes. Immunohistochemistry outlines the specific markers, including caudal-related homeobox protein (CDX2), homeobox protein Nkx-3.1 (NKX3-1), paired box gene 8 (PAX8), special AT-rich sequence-binding protein 2 (SATB2), thyroid transcription factor 1 (TTF-1), and splicing factor 1 (SF1) with the focus on the effectiveness of lineage-restricted transcription factors. Patients response to treatment can be evaluated by the gene expression profiling (GEP) test that also predicts tissue of origin (TOO). Tumor identified through gene profiling is sensitive to platinum/taxane therapy, others that are not TOO tumors are resistant to platinum/taxane. The new therapeutic method based on molecular profiling is associated with higher treatment response. In comprehensive genomic profiling, it is observed that there is at least one clinically appropriate genomic alteration in CUP that can influence the targeted therapy. The targeted therapeutic approach will not only improve the disease outcome but will also be cost-effective and save time from finding the primary site.

Fine Needle Biopsy of Malignant Tumors of the Liver: a Retrospective Study of 624 Cases from a Single Institution Experience

“…Recent studies have found that these unclassifiable neoplasms represent a heterologous group of tumors [18]. Many specific entities have been recently identified with new molecular and/or immunohistochemical tools, especially in the head and neck region [21][22][23][24][25]. Identification of these new entities is important for us to understand the epidemiology, etiology, tumor behavior, and most importantly, identify effective patient treatment [26].…”

Pineal Gland Metastasis From Poorly Differentiated Carcinoma of Unknown Primary Origin

“…The pathobiology of CUP remains to be elucidated; however, two hypotheses have been described to explain their inception. The first theory establishes that a tumor can develop without a premalignant lesion or primary tumor (10,11). The second theory postulates that metastatic progression occurs parallel to development of the primary lesion emphasizing that CUP metastases may be a premature event in tumorigenesis (10,11).…”

“…The first theory establishes that a tumor can develop without a premalignant lesion or primary tumor (10,11). The second theory postulates that metastatic progression occurs parallel to development of the primary lesion emphasizing that CUP metastases may be a premature event in tumorigenesis (10,11). Regardless of etiology, histological confirmation of a metastatic tumor is the fundamental basis of a diagnosis of CUP.…”

Radiologische Diagnostik von Kopf-Hals-Tumoren

“…Ist sowohl in der Bildgebung als auch der Endoskopie kein Tumor zu lokalisieren, sollte noch bevor systematische Biopsien erfolgen ein FDG-PET/ CT (▶ Abb. 9) durchgeführt werden [18]. Für die FDG-PET/CT wurde die Tumordetektionsrate, Sensitivität und Spezifität in einer Metaanalyse mit 44 %, 97 % und 68 % angegeben [19].…”

“…Kräftige FDG-Aufnahme sowohl im Primärtumor, als auch in den Lymphkontenmetastasen. 18 F-FDG PET, CT nativ , fusioniertes 18…”