Basal cell (myoepithelial) adenocarcinoma of the lung. First case with cytogenetic findings

We describe a case of lung carcinoma with myoepithelial differentiation, histologically analogous to the basal cell adenocarcinoma of salivary glands. The patient, a 76-year-old female, smoker, presented with a peripheral nodule of 1.5 cm in the lower lobe of her right lung. She was asymptomatic and the nodule was disclosed during the follow up program for a squamous cell carcinoma of the tongue surgically resected 2 years previously. The patient underwent surgery and a lobectomy with dissection of the ipsilateral hilar and mediastinal lymph nodes was performed. All the lymph nodes were tumor-free. 12 months after surgery the patient is well without evidence of disease. Microscopically, the tumour had a lobular architecture made up of lobules and solid aggregates of cells immersed in a fibrous stroma. The lobules were well circumscribed and sometimes the cells were arranged to form a peripheral palisade (Fig.1A). Variable amounts of eosinophilic basal lamina-like material were evident in the stroma and within the lobules, giving the tumour a cylindromatous appearance. Neoplastic cells were basaloid in appearance. They had a small to moderate amount of basophilic or amphophilic cytoplasm and oval nuclei with coarse chromatin and small nucleoli. Mitoses were numerous with atypical figures. In some aggregates, small glandular lumina were present lined by cells with the same characteristics as cells displaying solid growth on H&E stains (Fig. 1B). Lastly, sparse foci of squamous differentiation were also evident (Fig.1B inset). Immunohistochemically, most of the cells were diffusely positive with p63, calponin, smooth muscle actin, and cytokeratin 14, while cytokeratin 7 and EMA selectively stained the cells lining the glandular lumina (Fig. 2A). Anti-laminin antibody stained the basal lamina-like material. EGFR and CD10 were positive in 30% and 20% of the cells respectively. All the other antisera gave negative results. For cytogenetic analysis twenty metaphases were evaluated and two were found to have a composite karyotype: 46,X, -X del (1)(q21), +del (1) (p31) [cp2]./ 46,XX[18] (Fig.). To confirm these data, the cells were reseeded and metaphase spreading revaluated. One metaphase out of 16 evaluated showed the same alteration as found in the first examination. Myoepithelial carcinomas resembling basal cell adenocarcinoma of the salivary glands are rare in the lung. Yousem (1) firstly reported two pulmonary tumours identical to the present lesion. He named them “adenosquamous carcinoma” because of the presence of squamous foci. Subsequently, Cavazza et al (2) described the third case and suggested calling these pulmonary tumours with the same name of their counterpart in the salivary glands. Cytologically, these tumours may be worrisome. The cells have a basaloid, poorly differentiated appearance and vesicular nuclei with frequent mitoses. Neoplastic glands with a distinct biphasic pattern are not clearly evident on routine hematoxylin eosin (HE) stain. However, immunohistochemistry readily reveals the double, secretory and myoepithelial, components. Despite its cytologic appearance, BCA seems to behave as a low grade neoplasm: the patient reported by Cavazza et al (2) was free of disease 22 months after surgery and the present patient is well after 1 year. Therefore it is very important to recognize BCA and to distinguish this tumour from a metastasis or from other more aggressive neoplasms. Basaloid carcinoma (BC) of the lung (3) is an aggressive tumour with poor prognosis and a basaloid cytology very similar to BCA. However, BC does not show any feature of myoepithelial differentiation and , thus, immunohistochemistry can easily distinguish between the two. Epi-myoepithelial carcinoma (EMC) and adenoid cystic carcinoma (ACC) may show features similar to BCA. However, EMC and ACC lack squamous differentiation and, in addition, in these tumours the biphasic growth is easily recognized at H&E level. On the contrary, ...