Observations by G-banding and multicolor spectral karyotyping in a salivary gland basal cell adenoma.

Abstract

G-banding · Spectral karyotyping · Salivarygland · Basal cell adenomaSir, During the past two decades, we have performed system-atic cytogenetic studies of the most frequently occurringhistological subtypes of benign and malignant salivarygland tumors [7, 10, 13]. In our total material, compris-ing more than 400 tumors, there is no case of benign sal-ivary basal cell adenoma. This uncommonly diagnosedtumor type accounts for about 2–3% of all neoplasms inthe salivary glands [4]. The basal cell adenoma was orig-inally described by Kleinsasser and Klein in 1967 [3],who pointed out the resemblance of the tumor cells tothe basal cells of ducts in salivary glands. Here, we pres-ent the karyotypic findings based on G-banding andspectral karyotyping (SKY) in such a tumor.The patient was a 45-year-old woman who had beenaware of a painless swelling in her left parotid gland formore than 10 years. During this period there had been noincrease in size of the swelling. Clinical examinationshowed a well-demarcated, firm, non-tender and movabletumor in the lower and superficial part of the left parotidgland. A fine needle biopsy revealed sheets of monomor-phic cells with a basaloid appearance, some of whichformed tubular structures. A few small lumps of metachro-matic substance were also observed. Based on the cytolo-gy, two diagnoses were considered: a basal cell adenomaversus an adenoid cystic carcinoma. Subsequently, a super-ficial parotidectomy was performed. The surgical specimencontained a completely removed, unencapsulated but well-demarcated, firm and lobular tumor. It measured approxi-mately 0.9×0.9×1.0 cm. Histological examination revealedthe typical picture of a basal cell adenoma (Fig. 1). Therewere no areas with signs of infiltrative growth.Cytogenetic analysis was performed on short-term cul-tured tumor material [7]. Slides aged for 3 weeks wereused for SKY analysis. The conditions for pretreatment,hybridization (Sky Paint probe), post-hybridization washesand detection were essentially as recommended by themanufacturer (ASI-Applied Spectral Imaging Ltd., MigdalHa’Emek, Israel). Image acquisition was achieved usingthe SpectraCube system (ASI) mounted on a Zeiss Axioplan2 Imaging microscope, and the analysis of spectral imageswas performed using the SkyView software (ASI) [12].A total of 25 G-banded metaphase cells were karyo-typed. Of these, three cells had a normal karyotype. Of theremaining cells, 20 had an abnormal stemline (mainline)karyotype with two marker chromosomes, a der(7) and ader(13). The other two cells were doubling products of thestemline cells. Detailed analysis of the G-banded meta-phases and of seven metaphases analyzed using SKY al-lowed us to determine the composition of these markersand to precisely map the breakpoints. The stemline karyo-type was 46, XX, der(7)t(7;13)(p15;q32), der(13)inv(13)(q12q32)t(7;13)(p15;q32) (Fig. 2a, b). No other structuralchanges were detected in any of the cells studied.Only three cases of basal cell adenomas have previ-ously been studied cytogenetically [2]. All of them origi-nated from the parotid gland. One tumor had a normalkaryotype, the second had a hyperdiploid karyotype withtrisomy 8 as the sole anomaly, and the third case con-tained three closely related clones: 49, XX, +8, +8, +16 /98, idem × 2, der(9)t(1;9)(q24;p24), +18, -22 / 98, idem ×2, i(1q), der(9)t(1;9)(q24;p24). The only common abnor-mality observed among these four tumors (the presentcase included) is one or two extra copies of chromosome8 found in two of the tumors, suggesting that at least asubgroup of these tumors might be distinguished by tri-somy 8. Whether or not the 7;13-translocation and/orinv(13) recorded in the present case are recurrent in basalcell adenomas is at present unknown.