del(18)(p11) is a very rare structural anomaly found only in 24 cases with onco-hematological disorders. This deletion has been observed in both myeloid (14 cases) and lymphoid (10 cases) malignancies and has been predominantly associated with a complex karyotype. In all cases 18p- is presented as a single copy in the karyotype. The anomaly was determined by conventional cytogenetic as terminal deletion with sub-band location of the breakpoint in 18p11.2. Microarray comparative genome hybridization (aCGH) studies in patients with acute myeloid leukemia have demonstrated that the deleted segment in 18p could be also interstitial and variable in size as has been proven in other tumor associated deletions. Three submicroscopic deleted regions have been identified - 18p11.32-p11.31, 18p11.23 and 18p11.22-p11.21 (Itzhar et al, 2011).

Acute Myeloid Leukemia (AML)

del(18)(p11) is found in 9 cases ( 0.1% of all AML cases with an abnormal karyotype) (Alimena et al., 1981; Brodeur et al., 1983; GFCH, 1990; Lawler et al., 1990; Mohamed et al., 1993; Davey et al., 1995; Krauter et al., 1998; Babicka et al., 2007; Kasyan et al., 2010) - 1 case with M1 French-American-British (FAB) phenotype, 2 cases with M2, 1 case with M3, 1 case with M4, 1 case with M6 and 3 with AML, NOS (one diagnosed as therapy related AML). The sex ratio is significantly unbalanced, near M:F=3.5:1. The age is documented in 5 cases: 6 and 35 (M2), 59 (M3), 42 (M4) and 61 (M6).

In 5 cases del(18)(p11) is found in complex karyotypes and in one as a sole anomaly. Three cases are with -5/del(5q), two with +8 and one case of each of the following well known rearrangements: -7; del(17p); t(8;21)(q22;q22); t(17;20)(q21;q11) in a M3 ( RARA not checked). In one case both arms of chromosome 18 are affected- der(18)del(18)(p11)del(18)(q21). In 3 cases 18p- is associated with sex chromosome abnormalities - 2 with a loss of Y chromosome and one with del(X)(q26).

Other Myeloproliferative Disorders

del(18)(p11) is described in 2 cases (one male and one female) with chronic myeloid leukemia (CML) (Ohyashiki et al., 1997; Sun et al,. 2011), 2 cases (males) with a myelodysplastic syndrome (Cerretini et al., 2002; Volkert et al., 2014) and one case (female) with primary myelofibrosis (PMF) involving a lymph node (Hu et al., 2009).

In 2 cases with MDS and one case with CML del(18)(p11) is associated with a complex karyotype, in one case with CML it is a second event and in one case (with PMF) it is a sole anomaly. In the two cases with CML 18p- anomaly is present in additional deviating sub-clones (sidelines) and in one case with MDS in two clones with dic(17;20)(p11-12;q11) and dic(18;18)(p11;p11).

Acute Lymphoblastic Leukemia (ALL)

del(18)(p11) is found in 8 cases with ALL (0.08% of all ALL cases with an abnormal karyotype) (Oshimura et al., 1977; Kanerva et al., 2002; van der Burg et al., 2002; Soulier et al., 2003; Karst et al., 2006; Shin et al., 2011; Schmiegelow et al., 2012; Lundin et al., 2014). The sex ratio is significantly unbalanced, near M:F=1.7:1. The anomaly has been observed in young, as well as older patients (average age 22.6 years; range 5-65).

In 5 cases del(18)(p11) is found in complex karyotypes and in 3 cases it is accompanied with second anomalies - der(21) in two cases and dup(18q)(q11q11) in one (unrelated clone). In 4 of the 5 cases with complex karyotypes 18p- is associated with one or more deletions including 6p-, 9p-, 11q- and 12p- and in two cases with t(7;14)(p13;q32) and t(14;18)(q32;q21) (Shin et al., 2011), respectively.

Follicular lymphoma (FL)

del(18)(p11) is reported in 2 cases with FL (Bosga-Bouwer et al., 2003; Horsman et al., 2003). Both have hyperdiplpoid, highly complex karyotypes.

A tumor suppressor gene(s) (TSG) important to the described hematological malignances may be is involved in the molecular pathogenesis of del(18)(p11). A number of TSG candidates are mapped in the deleted segment 18p11.2->18pter including PTPN2 (18p11.21), LDLRAD4 (C18orf1) (18p11.21), RALBP1 (18p11.22), PPP4R1 (18p11.22), PTPRM (18p11.23), EPB41L3 (18p11.31), L3MBTL4 (18p11.31), TGIF1 (18p11.31), ZEP161 (18p11.31) and SMCHD1 (18p11.32). Almost all are implicated in the pathogenesis of a variety of solid tumors, but there are several lines of data suggesting that four of them (PTPN2, PTPRM, TGIF1 and SMCHD1) could also have a role in leukogenesis and respectively may act as TSG in the hematopoietic system.

T-ALL

NHL