The disclosure generally relates to the preparation of representative samples from clinical samples, e.g., tumors (whole or in part), lymph nodes, metastases, cysts, polyps, or a combination or portion thereof, using mechanical and/or biochemical dissociation methods to homogenize intact samples or large portions thereof. The resulting homogenate provides the ability to obtain a correct representative sample despite spatial heterogeneity within the sample, increasing detection likelihood of low prevalence subclones, and is suitable for use in various diagnostic assays as well as the production of therapeutics, especially “personalized” anti-tumor vaccines or immune cell based therapies.