In the group of malignant epithelial tumours of the lungs, adenocarcinomas belong to the non-small cell carcinomas (non-small cell lung cancer (NSCLC)), as opposed to small cell carcinomas (SCLC). Other NSCLCs of the lungs are: squamous cell carcinomas, adenosquamous carcinomas, large cell carcinomas, sarcomatoid carcinomas, carcinoid tumours, and salivary gland tumours.

KRAS (12p12) and EGFR (7p11) are mutated in 15% and 10% of NSCLCs, and PIK3CA (3q26), BRAF (7q34), and ERBB2 (17q12) are mutated in another 5% of NSCLCs. The presence of EGFR or KRAS mutations and translocations such as EML4/ALK or other tyrosine kinase fusions (see below), are mutually exclusive in lung adenocarcinoma.
Three tyrosine kinase receptors are recurrently found implicated in translocations: ALK (2p23), ROS1 (6q22), and RET (10q11). Kinase fusion positive (ALK, ROS1 and RET fusions) lung cancers are (almost) exclusively adenocarcinomas, at times squamous or adenosquamous carcinomas.
In a study of 16 patients with adenocarcinoma and one patient with large cell carcinoma, never-smokers have more often EGFR mutations or ALK-ROS1-RET translocations and smokers more often KRAS, TP53, BRAF, JAK2, JAK3 and mismatch repair gene mutations (Govindan et al., 2012).

Adenocarcinomas comprise 30% to 40% of lung cancers, with geographical variations, and it is becoming more prevalent. Tobacco smoking is the major cause of lung cancer of each histological subtype, but adenocarcinoma is more frequently found in non-smokers than any other histologic types of lung cancer.

Adenocarcinomas are more common in the peripheral lung (alveolar or bronchioalveolar cell) than in central location, and the visceral pleura is therefore frequently involved, with fibrosis. Patients with ALK, ROS1, or RET fusion transcripts are often younger nonsmoking female patients, with early lymph node metastases.

Presence of either solid signet ring cell or cribriform patterns with abundant extracellular mucus is frequently found in ALK-ROS1-RET translocations cases (Takeuchi et al., 2012; Yoshida et al., 2013).

- As said above, three membrane associated tyrosine kinase receptors are recurrently involved in translocations in adenocarcinomas: ALK, implicated with six possible different partners; ROS1, implicated with nine possible partners; RET, implicated with three possible partners. Other tyrosine kinases can also be involved (PDGFRA (4q12), DDR1 (6p21), FGFR2 (10q26), AXL (19q13), ...).
- Eight others genes were found implicated in two distinct translocations: APAF1 (12q23, structural core of the apoptosome), CCDC6 (10q21, structural constituent of the cytoskeleton), GOPC (6q22, ion channel binding protein), H19 (11p15, non-protein coding sequence), KDELR2 (7p22, receptor), KIF5B (10p11, motor protein), SFTPA2 and SFTPB (10q22 and 2p11, surfactant-associated proteins); 138 other genes were implicated once.

Targeted therapies: the treatments for NSCLCs have shown impressive clinical responses in patients with EGFR mutations treated with EGFR tyrosine kinase inhibitor therapy. ALK and ROS1 fusions proteins are both sensitive to treatment with the new ALK tyrosine kinase inhibitors, and clinical trials report an overall response rate of 57% in patients with ALK rearrangements. Cells expressing KIF5B/RET were found sensitive to multitargeted kinase inhibitors that inhibit RET. Therefore, more than 50% of the patients with lung adenocarcinoma may benefit from treatments with corresponding kinase inhibitors (Takeuchi et al., 2012).

In a study of 248 patients with NSCLC, the 2-year overall survival rates were 89% for EGFR, 73% for KRAS, 74% for ALK, and 62% for RET. There was no significant difference between patients with RET-positive and RET-negative tumors. Patients with EGFR mutations had a significantly longer overall survival than patients with KRAS mutations (Wang et al., 2012). Patients lacking EGFR mutations or translocations involving tyrosine kinases are left with a dismal 5-year survival rate of 15%.

The most frequent ALK fusion in adenocarcinomas of the lung is EML4/ALK (4% to 7% of cases), and the second is KIF5B/ALK (0.5%). ROS1 fusions are found in 1% to 2.5% of patients with NSCLCs (Davies et al., 2012; Yoshida et al., 2013). RET fusions occur in 1.4% of NSCLCs and 1.7% of lung adenocarcinomas (Takeuchi et al., 2012; Yoshida et al., 2013).
- ALK is implicated with six possible different partners: inv(2)(p21p23) or del(2)(p21p23) EML4/ALK, t(2;2)(p23;p22) STRN/ALK, t(2;3)(p23;q12) TFG/ALK, t(2;9)(p23;q31) ALK/PTPN3, t(2;10)(p23;p11) KIF5B/ALK and t(2;14)(p23;q32) KLC1/ALK;
- ROS1 is implicated with nine possible partners: t(1;6)(q21;q22) TPM3/ROS1, t(4;6)(p15;q22) SLC34A2/ROS1, t(5;6)(q33;q22) CD74/ROS1, t(6;6)(q22;q22) GOPC/ROS1, inv(6)(q22q25) EZR/ROS1, t(6;7)(q22;p22) KDELR2/ROS1, t(6;10)(q22;q21) CCDC6/ROS1, t(6;12)(q22;q14) LRIG3/ROS1, and t(6;20)(q22;q12) SDC4/ROS1;
- RET is implicated with three possible partners: inv(10)(p11q11) CCDC6/RET, inv(10)(p11q11) KIF5B/RET, and inv(10)(q11q11) NCOA4/RET.
These translocations lead to aberrant tyrosine kinase activation.

The eighty six translocations reported so far in adenocarcinomas of the lung greatly differ from that ones found in squamous cell carcinoma, or that ones found in small cell carcinoma. They are the following:

t(X;X)(p22;q13) EDA/MID1 (Seo et al., 2012)
t(X;1)(q23;q24) ACSL4/DCAF6 (Govindan et al., 2012)
t(X;20)(p11;p12) SPTLC3/MAOA (Seo et al., 2012)

t(1;1)(p36;p36) UBR4/ATP13A2 (Seo et al., 2012)
t(1;1)(p36;p34) ARHGEF16/TCTEX1D4 (Seo et al., 2012)
t(1;1)(p35;p35) SRSF4/SNRNP40 (Seo et al., 2012)
t(1;1)(p34;p32) FGGY/TESK2 (Majewski et al., 2013)
t(1;1)(p13;p12) IGSF3/MAN1A2 (Seo et al., 2012)
t(1;1)(p13;p12) VANGL1/HAO2 (Govindan et al., 2012)
t(1;1)(q24;q24) CD247/GPR161 (Imielinski et al., 2012)
t(1;6)(p32;q14) ZFYVE9/CGA (Seo et al., 2012)
t(1;6)(q21;q22) TPM3/ROS1 (Takeuchi et al., 2012)
t(1;19)(q23;p13) TCF3/PBX1 (Mo et al., 2013)

t(2;2)(p23;p22) STRN/ALK (Majewski et al., 2013)
inv(2)(p21p23) del(2)(p21p23) EML4/ALK (Rikova et al., 2007; Choi et al., 2008; Koivunen et al., 2008; Majewski et al., 2013)
t(2;2)(p22;p21) MAP4K3/PRKCE (Seo et al., 2012)
t(2;2)(q21;q22) MGAT5/HNMT (Seo et al., 2012)
t(2;2)(q24;q24) STK39/B3GALT1 (Imielinski et al., 2012)
t(2;2)(q33;q33) ADAM23/SGOL2 (Imielinski et al., 2012)
t(2;3)(p23;q12) TFG/ALK (Rikova et al., 2007)
t(2;8)(p11;p21) SFTPB/DPYSL2 (Seo et al., 2012)
t(2;9)(p23;q31) ALK/PTPN3 (Jung et al., 2012)
t(2;10)(p23;p11) KIF5B/ALK (Takeuchi et al., 2009; Wong et al., 2011)
t(2;10)(p11;q22) SFTPA2/SFTPB (Seo et al., 2012)
t(2;14)(p23;q32) KLC1/ALK (Togashi et al., 2012)
t(2;19)(q11;q13) XRCC1/MAL (Seo et al., 2012)

t(3;3)(p25;p25) TTLL3/MTMR14 (Imielinski et al., 2012)
t(3;3)(p24;p24) EOMES/SLC4A7 (Imielinski et al., 2012)
t(3;3)(p21;p14) CACNA2D3/FLNB (Govindan et al., 2012)
t(3;3)(q21;q22) MGLL/SLCO2A1 (Imielinski et al., 2012)
t(3;3)(q25;q25) CP/WWTR1 (Imielinski et al., 2012)
t(3;6)(p24;q16) UBE2E1/ASCC3 (Seo et al., 2012)

t(4;6)(p15;q22) SLC34A2/ROS1 (Davies et al., 2012; Rimkunas et al 2012; Seo et al., 2012; Takeuchi et al., 2012)
t(4;12)(q12;q12) SCAF11/PDGFRA (Seo et al., 2012)

t(5;5)(q12;q12) ERBB2IP/MAST4 (Seo et al., 2012)
t(5;5)(q13;q13) ARHGEF28/UTP15 (Imielinski et al., 2012)
t(5;5)(q31;q31) UBE2D2/MATR3 (Imielinski et al., 2012)
t(5;6)(q11;p22) IL6ST/KDM1B (Seo et al., 2012)
t(5;6)(q33;q22) CD74/ROS1 (Rikova et al., 2007; Davies et al., 2012; Rimkunas et al., 2012; Seo et al., 2012)
t(5;6)(q33;q22) ROS1/CD74 (Imielinski et al., 2012)
t(5;8)(p15;q22) CMBL/NDUFAF6 (Seo et al., 2012; Takeuchi et al., 2012)
t(5;10)(q35;q11) SGMS1/STK10 (Govindan et al., 2012)
t(5;12)(q33;q14) GRIP1/TNIP1 (Govindan et al., 2012)

t(6;6)(q22;q22) GOPC/ROS1 (Rimkunas et al., 2012; Suehara et al., 2012)
t(6;6)(q22;q22) TPD52L1/TRMT11 (Seo et al., 2012)
inv(6)(q22q25) EZR/ROS1 (Takeuchi et al., 2012; Yoshida et al., 2013)
t(6;7)(q22;p22) KDELR2/GOPC (Govindan et al., 2012)
t(6;7)(q22;p22) KDELR2/ROS1 (Govindan et al., 2012)
t(6;10)(q22;q21) CCDC6/ROS1 (Seo et al., 2012)
t(6;12)(q22;q14) LRIG3/ROS1 (Takeuchi et al., 2012)
t(6;12)(q24;q13-14) UTRN/OS9 (Seo et al., 2012)
t(6;20)(q22;q12) SDC4/ROS1 (Davies et al., 2012; Takeuchi et al., 2012)

t(9;9)(q34;q34) TUBB4B/COBRA1 (Imielinski et al., 2012)
t(9;12)(p13;q23) APAF1/TLN1 (Govindan et al., 2012)
t(9;12)(p13;q23) APAF1/UNC13B (Govindan et al., 2012)

inv(10)(p11q11) CCDC6/RET (Matsubara et al., 2012; Takeuchi et al., 2012; Wang et al., 2012)
inv(10)(p11q11) KIF5B/RET (Ju et al., 2012; Kohno et al., 2012; Lipson et al., 2012; Seo et al., 2012; Suehara et al., 2012; Takeuchi et al., 2012; Wang et al., 2012)
inv(10)(q11q11) NCOA4/RET (Wang et al., 2012)
t(10;10)(q11;q11) MARCH8/PRKG1 (Govindan et al., 2012)
t(10;10)(q25;q25) SHOC2/RBM20 (Imielinski et al., 2012)
t(10;12)(q26;q24) FGFR2/CIT (Seo et al., 2012)
t(10;19)(q22;q13) FTL/SFTPA2 (Seo et al., 2012)

t(11;11)(q13;q13) RBM14/FGF3 (Seo et al., 2012)
t(11;11)(q23;q23) HYOU1/C11ORF93 (Seo et al., 2012)
t(11;13)(q24;q14) APLP2/TNFSF11 (Seo et al., 2012)
t(11;14)(p15;q11) MMP14/H19 (Seo et al., 2012)
t(11;19)(p15;p13) H19/CALR (Seo et al., 2012)

t(12;12)(q13;q14) SLC16A7/MUCL1 (Seo et al., 2012)
t(12;12)(q15;q21) RAB21/FRS2 (Seo et al., 2012)
t(12;12)(q23;q24) TXNRD1/GPR133 (Seo et al., 2012)
t(12;16)(p12;q23) KRAS/CDH13 (Seo et al., 2012)
t(12;17)(q14;q25) RASSF3/TTYH2 (Govindan et al., 2012)

t(14;19)(q13;q13) AXL/MBIP (Seo et al., 2012)

t(15;15)(q22;q24) CYP1A2/SPG21 (Imielinski et al., 2012)
t(15;22)(q21;q12) MCM5/TRPM7 (Majewski et al., 2013)

t(16;16)(p13;p13) MSLN/WDR90 (Majewski et al., 2013)

t(17;17)(p13;p13) XAF1/FAM64A (Seo et al., 2012)
t(17;17)(p12;p11) TTC19/ATPAF2 (Seo et al., 2012)
t(17;17)(q11;q12) IKZF3/NF1 (Majewski et al., 2013)
t(17;17)(q23;q23) BCAS3/MAP3K3 (Seo et al., 2012)
t(17;21)(q24;q22) BRWD1/CCDC46 (Seo et al., 2012)

t(18;18)(q11;q11) LAMA3/RIOK3 (Majewski et al., 2013)
t(18;20)(p11;q13) PHACTR3/PTPRM (Imielinski et al., 2012)

t(19;19)(p13;p13) MIER2/NMRK2 (Seo et al., 2012)
t(19;19)(p13;p13) OAZ1/SF3A2 (Imielinski et al., 2012)
t(19;19)(q13;q13) LSM14A/SIPA1L3 (Seo et al., 2012)
t(19;19)(q13;q13) RHPN2/ANKRD27 (Govindan et al., 2012)