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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20) The presence of mucous cells and intra-alveolar mucin are the 2 critical mimickers of adenocarcinoma (Figure 7, A), and the notoriously bland cells of the lepidic pattern of mucinous carcinoma are also diagnostically challenging.
There was also a focal lepidic pattern of growth seen at the periphery of the specimen.
An example of the macroscopic features of invasive lung adenocarcinoma with a lepidic pattern.
The probability of finding 15 papillae in 1 microscopic field of view is much smaller, providing an additional argument that the proliferation represents cross-sections of lepidic pattern as opposed to true papillae.
Finally, there are often zones of transition from the lepidic pattern to the invasive pattern, and in the zones of transition there is often a change in nuclear grade as well as cellular morphology to a more columnar than cuboidal cell.
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 < .
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).
These relate to the discontinuation of the terms bronchioloalveolar carcinoma and adenocarcinoma, mixed subtype, as well as the introduction of micropapillary as a new histologic subtype, the term lepidic pattern for the former bronchioloalveolar carcinoma growth pattern, and the specific term invasive mucinous adenocarcinoma for overtly invasive tumors previously classified as mucinous bronchioloalveolar carcinoma.
Minimally invasive adenocarcinoma is a small, solitary adenocarcinoma ([less than or equal to] 3 cm), with a predominantly lepidic pattern and invasion of 5 mm or less in greatest dimension in any one focus (Table 2).
Tumors with the lepidic pattern predominant do relatively well, whereas those that are predominantly solid or micro-papillary do relatively badly.