If there is overt evidence of squamous differentiation, such as keratinization, keratin pearls, and/or intracellular bridges:
– Squamous cell carcinoma
If there is evidence of glandular differentiation, such has gland formation or cytoplasmic mucin:
– Adenocarcinoma (see comment)
COMMENT: The biopsy shows an adenocarcinoma with *** growth patterns.
[Fill in the blank with a combination of: Lepidic, Acinar, Papillary, Micropapillary, and/or Solid]
If there is an adenocarcinoma with pure lepidic growth in the biopsy:
– Adenocarcinoma with a lepidic pattern (see comment)
COMMENT: The biopsy shows an adenocarcinoma with exclusively lepidic growth in the biopsy. The differential diagnosis includes adenocarcinoma in situ and the lepidic component of an invasive adenocarcinoma. Clinical and radiographic correlation is recommended.
If there is an adenocarcinoma with unique features:
– Mucinous adenocarcinoma
– Adenocarcinoma with colloid features
– Adenocarcinoma with fetal features
If there is an adenocarcinoma in the lung that essentially looks like colon cancer and stains like colon cancer
– Adenocarcinoma with enteric features (see comment)
COMMENT: The biopsy shows an adenocarcinoma with abundant dirty necrosis and an immunohistochemical profile that is often seen with enteric/intestinal adenocarcinoma. Clinical correlation is required to exclude a metastasis from the colon/gastrointestinal tract. If a metastasis has been excluded, then these findings could be compatible with a primary lung enteric-type adenocarcinoma.
If a tumor is not clearly squamous morphologically, but the IHC profile supports squamous (e.g., p40 +)
– Non-small cell carcinoma, favor Squamous cell carcinoma
If a tumor is not clearly adenocarcinoma morphologically, but the IHC profile supports adenocarcinoma (e.g., TTF1 +)
– Non-small cell carcinoma, favor Adenocarcinoma
If a tumor is not clearly categorizable as adenocarcinoma or squamous cell carcinoma by IHC and morphology (e.g., TTF1 and p40 -)
– Non-small cell carcinoma, Not Otherwise Specified
If a tumor is not clearly morphologically adenocarcinoma or squamous cell carcinoma and tumor is very scant and tissue is anticipated to be needed for additional studies, so additional work-up is forgone
– Non-small cell carcinoma, Not Otherwise Specified (see comment)
COMMENT: The biopsy shows a non-small carcinoma without clear squamous cell carcinoma or adenocarcinoma features morphologically. Given the limited material, additional work up with immunohistochemical stains to further categorize the tumor was not pursued to save as much tissue as possible for other anticipated additional studies. However, they could be performed if requested. Clinical and radiographic correlation is recommended.
– Carcinoid Tumor/Neuroendocrine Tumor, Not Otherwise Specified (see comment)
COMMENT: The lung biopsy shows a carcinoid tumor. No mitotic figures or necrosis are identified in this limited biopsy, compatible with a traditional carcinoid tumor. However, given the limited sampling, final classification is deferred. The proliferation index by staining for Ki67 is ***%.
– Small cell carcinoma
– Large cell neuroendocrine carcinoma
Large cell neuroendocrine carcinoma, in many circumstances, cannot be definitively diagnosed on a small biopsy as there must be both morphologic and IHC evidence of NE differentiation.
– Non-small cell carcinoma, possible Large cell neuroendocrine carcinoma (see comment)
COMMENT: The biopsy shows a tumor with a suggestion of trabecular growth with peripheral palisading and large cells with vesicular chromatin and prominent nucleoli and abundant cytoplasm. Immunohistochemical stains demonstrate neuroendocrine differentiation. Together, these findings raise the possibility of large cell neuroendocrine carcinoma.