This is a histopathology slide of lung tissue prepared for light microscopy, stained with Hematoxylin and Eosin (H&E). The sample demonstrates a lepidic adenocarcinoma pattern, with neoplastic columnar epithelial cells proliferating along preexisting alveolar walls (lepidic growth) and partially preserving alveolar architecture. In the lower half of the field, neoplastic cells line and expand the alveolar septa, producing subtle crowding of nuclei with mild to moderate atypia and low mitotic activity. There is no conspicuous desmoplasia or stromal invasion evident in this view, although invasion may be focal and better assessed on additional sections. Some tumor cells show intracellular mucin. The background lung parenchyma displays relatively preserved air spaces and occasional inflammatory cells. The overall histology is compatible with lung adenocarcinoma, lepidic predominant or adenocarcinoma in situ spectrum, and could represent early invasive adenocarcinoma depending on invasion assessment in deeper sections. Clinically, lepidic growth pattern carries relatively favorable prognosis compared with other invasive adenocarcinoma subtypes when invasion is limited. This image is suitable for educational illustration of pulmonary adenocarcinoma subtypes, differential diagnosis with atypical adenomatous hyperplasia and adenocarcinoma in situ, and correlation with radiologic ground-glass opacities. Further sections may reveal invasive components not seen here. Correlation with radiologic imaging can aid staging.

This image depicts a hematoxylin and eosin stained histology slide of lung parenchyma showing invasive non-mucinous adenocarcinoma with a lepidic growth pattern. The neoplastic epithelium lines and expands the alveolar septa with columnar to cuboidal atypical pneumocytes resembling type II pneumocytes or Clara cells. Lepidic spread is evident as neoplastic cells proliferate along preexisting alveolar walls, often preserving underlying architecture. In this specimen, components typical of lepidic growth may co-occur with minor areas showing acinar, papillary, micropapillary or solid differentiation, illustrating the histologic continuum described in contemporary classification. The lepidic areas frequently lack fibrovascular cores, contrasting with true papillary architecture; mucin production is not prominent in the shown fields. The tumor demonstrates nuclear atypia, mitotic activity may be inconspicuous, and alveolar spaces remain partly preserved by tumoral lining, contributing to a morphological impression of invasive lepidic adenocarcinoma. Correct classification requires semi-quantitative assessment of the lepidic component versus invasive patterns, as per the WHO 2015 guidelines, since prognosis and therapeutic implications depend on predominant histology. This image is relevant for pathology education, differential diagnosis discussions, and correlation with radiologic ground-glass opacities. The image serves as a reference for grading lepidic dominance and for correlating histology with radiographic patterns in thoracic oncology education and research.

Histopathology image depicts primary non-mucinous lung adenocarcinoma with a lepidic growth pattern. Hematoxylin and eosin stained sections show cuboidal to low-columnar malignant cells lining alveolar septa and projecting into alveolar spaces, creating a characteristic lepidic architecture with preservation of alveolar outlines and minimal desmoplasia. Scattered anthracotic pigment granules are present within the alveolar septa and spaces. The inset immunohistochemical panel demonstrates strong nuclear positivity for TTF-1 in tumor cells, supporting a pulmonary origin and helping differentiate from metastatic carcinomas that are typically TTF-1 negative (with exceptions such as some thyroid metastases). The described immunoprofile of primary lung adenocarcinoma commonly includes CK7+, TTF-1+, Napsin A+, EMA+, CEA+, with CK20-, CDX2-, MUC2- in many cases, though CDX2 can be positive in mucinous variants. Overall, the image emphasizes non-mucinous histology, lepidic polarity, and the diagnostic value of TTF-1 staining for establishing a primary lung adenocarcinoma versus metastasis. Clinically relevant for diagnosis, prognosis assessment, and guiding molecular testing and therapeutic planning.

Imaging modality: Light microscopy of hematoxylin and eosin (H&E) stained lung tissue section. Primary subject: small cell lung carcinoma (SCLC) tumor cells derived from bronchogenic carcinoma. Specimen: bronchial/lung parenchyma biopsy; histologic section prepared from paraffin-embedded tissue, typically 4-5 micrometers thick. Imaging perspective: high-magnification cellular view under brightfield illumination. Visual features: the tumor shows dense sheets and clusters of small, round to oval cells with scant cytoplasm and ill-defined cytoplasmic borders, producing a densely packed, blue-gray appearance on H&E. Nuclei are hyperchromatic with finely dispersed granular chromatin giving a salt-and-pepper pattern; nucleoli are absent or inconspicuous. Nuclear molding is a constant finding. Mitotic activity is markedly increased, with numerous mitotic figures; necrosis is commonly present within tumor nests. The morphology is that of a high-grade neuroendocrine carcinoma, with little cytoplasm and abrupt cell borders. Background tissue often contains necrotic debris and crush artifacts near tumor clusters. This histology supports differentiation from non-small cell lung carcinomas, in which chromatin may be coarser and nucleoli more conspicuous. Clinically, SCLC is aggressive with early metastatic potential and a distinct therapeutic approach; histology guides diagnosis, prognosis, staging, and treatment planning, including chemotherapy and radiotherapy regimens and consideration of paraneoplastic syndromes.

Imaging modality: light microscopy of hematoxylin and eosin (H&E) stained lung tissue biopsy; specimen: lung parenchyma, central airways, consistent with small cell lung carcinoma (SCLC). The histology shows sheets and clusters of very small round to oval cells with scant cytoplasm and ill-defined borders, resulting in a high nuclear-to-cytoplasmic ratio. Nuclei are hyperchromatic with finely dispersed granular chromatin described as salt-and-pepper, and nucleoli are absent or inconspicuous. Nuclear molding is a constant and defining feature, with intimate contiguity of nuclei that distorts cell borders. Mitotic activity is brisk and necrosis is commonly present, reflecting the high-grade nature of SCLC, which by definition is high-grade and lacks a conventional grading scale. The tumor often displays crush artifact and necrotic debris in intercellular spaces. The morphology helps distinguish SCLC from non-small cell carcinoma, where chromatin tends to be clumpy and nucleoli are more conspicuous. Immunohistochemistry may further support diagnosis, with neuroendocrine markers such as synaptophysin, chromogranin A, and CD56 typically positive, and TTF-1 often variably expressed. Clinically, these findings correlate with aggressive behavior, early metastatic potential, and a treatment paradigm dominated by systemic chemotherapy and radiotherapy. The image is essential for education and reference in pathology, oncology, and thoracic medicine. Educational reference material.

Imaging modality and technique: Brightfield light microscopy of a hematoxylin and eosin–stained lung biopsy section. Primary subject: small cell carcinoma of the lung (SCLC), a high‑grade neuroendocrine carcinoma commonly arising centrally in smokers. Specimen: bronchoscopic or percutaneous core biopsy tissue displaying dense cellularity within lung parenchyma. Morphologic features: numerous small, round to oval cells with scant cytoplasm and ill‑defined borders, forming sheets and clusters. Nuclear characteristic: hyperchromatic, finely dispersed salt‑and‑pepper chromatin with absent or inconspicuous nucleoli and pronounced nuclear molding. Cytoplasm is tenuous, giving a characteristic high nuclear‑to‑cytoplasmic ratio. Mitotic activity is brisk with frequent atypical mitoses; extensive necrosis is often present, contributing to geographic tumor necrosis on histology. Background stroma is usually fibrotic or desmoplastic, and crush artifacts may accentuate nuclear crowding. These features collectively define a high‑grade phenotype with aggressive biology. Diagnostic significance: when present, these findings support SCLC diagnosis and guide rapid systemic chemotherapy and radiotherapy planning. Context and differential: morphological distinction from non‑small cell lung carcinoma relies on chromatin pattern (finely dispersed, no clumps) and nucleoli, rather than nuclear size or neuroendocrine differentiation. Correlation with immunohistochemistry (e.g., synaptophysin, chromogranin A) reinforces the diagnosis and informs prognosis and treatment planning.