Solid Tumor — Abnormal Mass of Tissue

A solid tumor is a discrete, localised collection of cells that have lost their normal regulatory mechanisms for growth. These growths can be non-cancerous (benign) or cancerous (malignant). Malignant solid tumors have the capacity to invade adjacent tissues and potentially shed cells into the bloodstream or lymphatic system, establishing secondary growths known as metastases.

Clinicians broadly categorise malignant solid tumors into carcinomas and sarcomas. Carcinomas arise from epithelial tissues that line organs and internal cavities, representing the majority of adult cancers. Sarcomas originate in mesenchymal tissues, including bone, cartilage, muscle, fat, and blood vessels. In contrast, haematological malignancies do not form distinct structural masses.

Identifying a solid tumor provides the starting point for cancer staging, risk assessment, and personalised treatment planning. Its physical dimensions, exact location, and relationship to neighbouring organs directly influence whether surgery is feasible. Pathological examination of tumor tissue clarifies the cellular origin, histologic grade, and biological aggressiveness. Furthermore, sampling the tumor yields vital tissue for genomic profiling, helping oncologists select targeted medicines or immunotherapy.

Solid tumors are typically detected using diagnostic imaging, including computed tomography (CT), magnetic resonance imaging (MRI), ultrasound, and positron emission tomography (PET). Definitive diagnosis requires a tissue biopsy, such as a core needle biopsy or surgical excision. Pathologists perform immunohistochemistry and molecular profiling to evaluate key biomarkers, such as HER2, ER, PR, EGFR, BRAF, and PD-L1.

Solid tumors encompass most human malignancies. Common examples include breast cancer, non-small cell lung cancer, prostate cancer, and colorectal cancer. Other types include renal cell carcinoma, ovarian cancer, pancreatic cancer, melanoma, and rarer malignancies such as osteosarcoma, soft tissue sarcomas, and primary central nervous system tumors like glioblastoma.

Management often involves local therapies, notably surgical resection to remove the mass and targeted radiotherapy to destroy residual cells. Systemic treatments—including cytotoxic chemotherapy, molecularly targeted therapies, and immune checkpoint inhibitors—are employed neoadjuvantly to shrink tumors prior to surgery, adjuvantly to clear micro-metastatic disease, or as primary treatment for inoperable tumors.