Cancer of unknown primary

Testicular cancer is the most common solid tumor in men aged 15 to 35 and is usually cured even when metastatic, because germ cell tumors are exquisitely chemosensitive. A painless testicular mass is worked up with scrotal ultrasound and serum tumor markers, radical inguinal orchiectomy establishes the diagnosis and provides local control, and post-orchiectomy markers plus CT staging then guide surveillance, radiation, retroperitoneal lymph node dissection, or cisplatin-based chemotherapy.

Breast cancer is a malignancy of ductal or lobular epithelium, most often presenting as a firm, painless mass in the upper outer quadrant. Diagnosis rests on core needle biopsy with estrogen, progesterone, and HER2 receptor testing, and first-line treatment pairs breast-conserving surgery or mastectomy with sentinel node biopsy, radiation, and receptor-guided systemic therapy such as tamoxifen or trastuzumab.

Epithelial ovarian cancer is the most lethal gynecologic malignancy because nonspecific symptoms and the absence of an effective screening test mean most women present with stage III or IV disease. Diagnosis rests on pelvic examination, cancer antigen 125 (CA-125), and transvaginal ultrasonography followed by surgical staging; treatment is cytoreductive surgery plus platinum-taxane chemotherapy, with olaparib maintenance in breast cancer susceptibility gene (BRCA)-mutated disease.

Head and neck squamous cell carcinoma arises from the mucosal epithelium of the oral cavity, pharynx, and larynx along two pathways, tobacco/alcohol-driven and HPV-16-driven oropharyngeal disease, presenting with site-specific symptoms culminating in a new neck mass. Diagnosis requires laryngoscopy and biopsy of the primary with p16 testing, and treatment is single-modality surgery or radiation for early stage, cisplatin-based chemoradiation for locally advanced disease, and checkpoint inhibitors or cetuximab for recurrent or metastatic disease.

Lung cancer is the leading cause of cancer death worldwide, split into non-small cell lung cancer (NSCLC, 80% of cases: adenocarcinoma, squamous cell, large cell) and small cell lung cancer (SCLC, 10-15%), both driven overwhelmingly by cigarette smoking. Diagnosis requires tissue histopathology, staging drives treatment (TNM staging for NSCLC, limited versus extensive stage for SCLC), and management ranges from lobectomy in early-stage disease through concurrent chemoradiation and consolidation immunotherapy in locally advanced disease to targeted tyrosine kinase inhibitors, immune checkpoint inhibitors, or platinum-based chemotherapy in metastatic disease.

Prostate cancer is the most commonly diagnosed cancer in men, usually found through an elevated PSA in an asymptomatic patient, with risk stratified by PSA, Grade Group (Gleason score), and TNM stage. Localized low-risk disease is often managed with active surveillance, while higher-risk and metastatic disease require radiation, surgery, or androgen deprivation therapy escalated through castrate-sensitive and castrate-resistant phases.

Non-Hodgkin lymphoma is a heterogeneous group of B-cell (about 85%) and T-cell lymphoid malignancies that spread noncontiguously and often involve extranodal sites, ranging from indolent follicular lymphoma to aggressive diffuse large B-cell lymphoma to highly aggressive Burkitt lymphoma. Diagnosis requires excisional or core biopsy with flow cytometry and cytogenetics, Ann Arbor staging with PET-CT, and treatment is subtype-specific, from observation to R-CHOP to intensive Burkitt regimens with aggressive tumor lysis and CNS prophylaxis.

Hodgkin lymphoma is a B-cell malignancy defined by Reed-Sternberg cells that classically presents with painless, contiguously spreading cervical or mediastinal lymphadenopathy in a young adult, and it is confirmed by excisional lymph node biopsy. Ann Arbor/Lugano stage and interim PET response drive risk-adapted ABVD chemotherapy with or without radiation, and most patients are cured.

Colorectal cancer is an adenocarcinoma that arises through the adenoma-carcinoma sequence and presents differently by location, with right-sided tumors causing occult bleeding and iron-deficiency anemia and left-sided tumors causing obstruction and hematochezia. Colonoscopy with biopsy confirms the diagnosis, TNM staging on CT chest/abdomen/pelvis with CEA guides treatment, and management ranges from surgical resection alone for localized disease to adjuvant FOLFOX for node-positive colon cancer, neoadjuvant chemoradiation for rectal cancer, and molecularly targeted systemic therapy for metastatic disease.

Melanoma is a malignant tumor of melanocytes recognized by the ABCDE criteria (asymmetry, border irregularity, color variation, diameter greater than 6 mm, evolving) and confirmed by complete excisional biopsy that captures full lesion thickness. Treatment starts with wide local excision sized to the Breslow tumor depth, adds sentinel lymph node biopsy for deeper lesions, and escalates to BRAF/MEK-targeted therapy or checkpoint immunotherapy for metastatic disease.

Soft tissue sarcoma is a diverse group of mesenchymal malignancies of fat, muscle, nerve, vessel, and fibrous tissue, confirmed only by biopsy and staged mainly by histologic grade and hematogenous (usually pulmonary) spread. A mass 5 cm or larger, deep to fascia, fixed, rapidly enlarging, recurrent, or painful without explanation should be imaged and biopsied before any excision.

Malignant spinal cord compression (metastatic epidural spinal cord compression) is an oncologic emergency from vertebral metastasis that requires whole-spine MRI within 24 hours, immediate high-dose dexamethasone, and urgent radiotherapy or surgical decompression to prevent irreversible paralysis.

Superior vena cava (SVC) syndrome is obstruction of blood flow through the SVC, most often from extrinsic compression by a mediastinal malignancy (lung cancer causes about 75% of cases) or, less commonly, catheter-related thrombosis. Contrast-enhanced chest CT establishes the diagnosis. Unless stridor, cerebral edema, or hemodynamic compromise demand emergency endovascular stenting, tissue biopsy precedes treatment, which targets the underlying malignancy with chemotherapy, radiation, or surgery.

Neutropenic fever is an oncologic emergency defined as a single oral temperature of 38.3 C or higher, or 38.0 C sustained for 1 hour, with an ANC of 500/microL or lower, most often during the chemotherapy nadir. Management is empiric antipseudomonal beta-lactam therapy within 60 minutes, with vancomycin, antifungal therapy, and growth factors added only for specific indications.