BAC pattern

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BAC pattern

Bronchioloalveolar carcinoma pattern. A term of art referring to a so-called lepidic (hobnail-like cells spreading across a surface) growth pattern of a tumour that mimics classic bronchioloalveolar carcinoma.
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References in periodicals archive ?
Among the cases with adenocarcinoma (AC) showing PD-L1 expression, a solid pattern was predominant in 5 and a lepidic pattern was predominant in 2 cases.
A discontinuous lepidic pattern can be seen at the periphery of the lesion, and adjacent alveolar spaces may contain mucin.
There was also a focal lepidic pattern of growth seen at the periphery of the specimen.
(52) In some instances, tumors that metastasize or grow in the interstitium, including squamous cell carcinoma, can induce a pneumocyte reaction that can be sufficiently atypical as to raise a concern for lepidic pattern adenocarcinoma (Figure 4, C).
The presence of STAS is an exclusion point in the diagnosis of minimally invasive adenocarcinoma (MIA), a small, solitary adenocarcinoma ([less than or equal to] 3 cm) with predominantly lepidic pattern and invasion extending 5 mm or less.
(c) Solitary adenocarcinoma (not more than 3 cm in greatest dimension), with a predominantly lepidic pattern and not more than 5 mm invasion in greatest dimension in any one focus.
An example of the macroscopic features of invasive lung adenocarcinoma with a lepidic pattern. Central firm area corresponds to tumor invasion, whereas the peripheral, ill-defined area matches the lepidic pattern.
If the alveolar walls are covered with tumor cells (ie, lepidic pattern), this may be mistaken for a papillary carcinoma (2,6) (Figure 1, C and D).
As we have over the decades come to better understand lung neoplasia and preneoplasia, bronchioloalveolar carcinoma (far from being understood as a single, specific lesion as it was originally considered) has leant its appellation to 5 clinically and pathologically distinct entities, namely, 3 nonmucinous lesions (adenocarcinoma in situ, minimally invasive adenocarcinoma, and adenocarcinoma with a prominent lepidic pattern) and 2 mucinous lesions (mucinous adenocarcinoma in situ and mucinous adenocarcinoma).
The predominant pattern seen in the EGFR-mutant-positive lung cancer group was lepidic (44%) as compared to patients with wild-type gene, whose tumors exhibited acinar pattern in 69% and lepidic pattern in 15% of cases; P < .001 (Figure 3).
Two cases with lepidic pattern and showing elastin in the fibrovascular cores are described.
Lepidic pattern of adenocarcinoma, characterized by noninvasive surface alveolar growth of tumor cells (hematoxylin-eosin, original magnification X200).