Bovine hepatocellular carcinoma histomorphologically and comparative pathologically analogous to human lymphocyte-rich hepatocellular carcinoma.

Human lymphocyte-rich hepatocellular carcinoma (LrHCC), a very rare HCC subtype associated with a favourable prognosis, has been debated on its existence as a distinct entity. Although HCC has been reported in all species of domestic animals, primary hepatic neoplasia similar to or identical with LrHCC has not been reported in cattle. Necropsy of an 8-year-old Holstein-Friesian slaughtered dairy cow revealed the presence of a hepatic neoplasm that was verified histopathologically as very similar to LrHCC on the basis of histomorphological and comparative pathological features. Not only did the neoplasm have histopathological features diagnostic of HCC, but it was also infiltrated by numerous CD3 T cells. The more intense the T-cell infiltrates, the more collapsed the growth pattern of the cancer cells, and cancer cell nests in the most advanced stage of cancer progression were enclosed within fibrotic connective tissues intermixed with massive T-cell infiltrates, leaving only a trace of tumour. Most likely, rather than providing evidence to substantiate a distinct variant of HCC, the massive intratumoural T-cell infiltrates in this bovine hepatic neoplasm reflected a host immune response against HCC cells resulting in spontaneous partial regression.