Basal-cell adenoma of parotid. Difficulty of differentiation from adenoid cystic carcinoma on aspiration biopsy

Two cases of basal-cell adenoma (basaloid monomorphic adenoma, dermal analogue tumor) seen in a one-year period were subjected to fine needle aspiration biopsy and subsequent histologic confirmation. Two cases of adenoid cystic carcinoma occurring in the parotid region were selected for comparison; a great similarity between the two types of tumors was noted. On aspiration smear both lesions consisted of clusters and sheets of uniform, small, regular cells with scant basophilic cytoplasm and regular round or oval bland nuclei. The smears contained varying amounts of homogeneous, pale, eosinophilic stromal substance within and around the cell clusters. Individual cell differences between the two lesions were minimal, with the adenoid cystic carcinomas tending to exhibit more nuclear hyperchromatism and irregularity; the architectural arrangements of the cell clusters and the stromal substance permitted differentiation between the two lesions.     

Genetic association of a GABAA receptor γ2 subunit variant with severity of acute physiological dependence on alcohol

The ultimate goal of quantitative trait locus (QTL) mapping is to identify the genes affecting complex traits. Using animal models, we recently identified QTLs on mouse Chromosomes (Chrs) 1, 4, and 11 affecting genetic predisposition to acute alcohol withdrawal. Among mice derived from the C57BL/6J (B6) and DBA/2J (D2) inbred strains, the locus identified on Chr 11 (∼20 cM) accounted for 12% of the genetic variability in withdrawal liability. Candidate genes in proximity to this QTL encode the γ₂, α₁, and α₆ subunits of GABA_A receptors. The present studies identify a polymorphism between the B6 and D2 strains in the γ₂ subunit gene, Gabrg2, and expand genotypic analysis to their BXD recombinant inbred strains. This polymorphism predicts a difference in amino acid sequence (Ala-11 vs. Thr-11) within the extracellular amino-terminal region of the γ₂ subunit. Analysis using BXD strain means for acute alcohol withdrawal severity suggests that the γ₂ subunit polymorphism is genetically correlated with alcohol withdrawal severity. This is the first report that QTL mapping for an alcohol-related trait has successfully led to the identification of a polymorphic candidate gene product that is genetically associated with the trait. Received: 15 September 1998 / Accepted: 8 October 1998