BALB/c mice are particularly well known for the production of plasmacytoma on injection with mineral oil, forming the basis for the production of monoclonal antibodies. Although not all BALB/c substrains have been examined for plasmacytoma induction, substrains derived from the Andervont (An) lineage (which includes BALB/cByJ) typically are susceptible, while those descended from BALB/cJ are resistant. Mammary tumor incidence is normally low, but infection with mammary tumor virus by fostering to MMTV+ C3H mice dramatically increases tumor number and age of onset. BALB/c mice develop other cancers later in life, including reticular neoplasm, primary lung tumors, and renal tumors. Rare spontaneous myoepitheliomas arising from myoepithelial cells of various exocrine glands have been observed in both BALB/cJ and BALB/cByJ substrains. A deficiency of Acads (acyl-Coenzyme A dehydrogenase, short chain) leads to severe organic aciduria. BALB/cByJ develop a fatty liver upon fasting or dietary fat challenge and become hypoglycemic after an 18-hour fast. BALB/cByJ mice have the advantage of better reproductive performance and less aggression than mice of the BALB/cJ substrain. A 2022 study found vaginal septa in 21% of BALB/cByJ females. BALB/c mice are predisposed to dystrophic cardiac calcinosis (mineralization of cardiac tissues). Using <a href="https://www.jax.org/strain/001026">BALB/cByJ</a> and <a href="https://www.jax.org/strain/000651">BALB/cJ</a> mice obtained from The Jackson Laboratory, a study by the laboratory of Dr. Steven Taffet reports that BALB/cByJ mice exhibited more frequent and severe calcium deposition (44/49; 90% at 5 weeks of age) than did BALB/cJ (1/6; 17% at 5 weeks of age) or other BALB/c substrains [Glass et al. 2013 Comp Med 63: 29 (<a href="https://pubmed.ncbi.nlm.nih.gov/23561935/">PMID:23561935</a>)].

Mice of this substrain of BALB/c, among other differences, have better reproductive performance and less aggression than mice of the BALB/cJ substrain (Stock No. <a href="https://www.jax.org/strain/000651"">000651</a>).