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Pathology report: Left lower lobe lung, Tumor Size: Greatest dimension: 3.0 cm Additional dimensions: 2.5 x 2.0 cm; Tumor Focality: Unifocal; Histologic Type: Invasive adenocarcinoma Solid predominant with mucin production; Histologic Grade: G3: Poorly differentiated. Is the correct histology for this case 8230/3 (rule H5) or 8255/3 (rule H6)?

Immunostain results of the malignant cells show strong staining with p63 and negative staining with TTF-1 and Napsin. Rare cells stain with CK7. Findings are most compatible with squamous cell carcinoma. The patient is treated as if he has squamous cell carcinoma. The new histology coding rules say you cannot use ambiguous terms which modify the histology to code the histology. So is this 8010/3?

Per Mayo consulting pathologist, the final diagnosis on this right lung biopsy is: SMARCA4-deficient malignant neoplasm (see Comment). Comment: Sections show a poorly-differentiated malignant neoplasm without any apparent glandular, squamous, or stromal differentiation. The tumor near totally replaces the underlying lung tissue without recognizable underlying alveolar parenchyma. Immunohistochemical stains performed at Mayo Clinic (Oscar keratin, INSM1, NUT, S100, desmin and BRG1 protein encoded by SMARCA4 gene) demonstrate that the malignant cells are positive for Oscar keratin (rare cells only), synaptophysin (weak/patchy) and p63 (focal) while negative for the remaining antibodies tested. Of note, SMARCA4 stain is negative in the tumor cells. Thus, this tumor can be categorized as a SMARCA4-deficient malignant neoplasm, which is known to be an aggressive malignancy, likely represent a SMARCA4-deficient thoracic sarcoma, a recently described entity. SMARCA4-deficient carcinomas in the lung have been reported to be mostly adenocarcinomas or squamous cell carcinomas, which would not fit for this case. Please refer to a paper published by our group (Sauter JL et al. Mod Pathol 2017;30:1422-32.

The patient was diagnosed with a biopsy-proven 12/2020 LUL SCC treated with radiation only, followed by a right hilar lymph node biopsy in 07/2022, that proved “metastatic pulmonary adenocarcinoma” per pathology and treated with radiation, followed by a biopsy-proven 12/2022 RLL SCC to be treated with immunotherapy only. The imaging never definitively identified a lung tumor that can be assumed to be a primary adenocarcinoma tumor.  In 06/2022, a PET scan only described a “strongly PET positive Rt inferior hilar LN vs infrahilar pulmonary mass,” as well as the subsequently biopsy-proven SCC in the RLL (12/2022 SCC primary). The biopsy path indicates this was a right hilar lymph node metastasis and does not indicate this is an infrahilar pulmonary mass. No other PET positive pulmonary lesions were seen at the time.

The oncologist’s assessment indicates the right hilar node was the only positive finding on the biopsy, and it was unclear if this right hilar node metastasis was from the left lung or if the primary was “not detectable.” The oncologist summarized this as a LUL lung lesion radiated for SCC, a right hilar lesion radiated for adenocarcinoma, and a RLL lung lesion on pathology found to be SCC.

Should the interval occurring metastatic adenocarcinoma be accessioned as a separate lung, NOS primary based on the histology difference? While the Solid Tumor Rules do not apply to metastasis, the oncologist did treat these three malignancies separately and does not indicate the hilar lymph node metastasis was felt to be from either SCC primary.

For example, pathologic diagnosis is non-small cell carcinoma with squamous features. The medical oncologist describes this as squamous cell carcinoma and begins treatment regimen. As I interpret the rules, we would use code 8046, non-small cell carcinoma, because of instruction 2 and the fact that features is not included in the list of ambiguous terminology.

Bilobectomy revealed two tumors, adenocarcinoma in the right middle lobe and bronchioalveoar carcinoma non-mucinous type in the right upper lobe. MP/H rule M10 states that tumors with non-small cell carcinoma (8046) and a more specific non-small cell type (chart 1) are a single primary. Does rule M10 apply to only those cases for which one tumor is stated to be non-small cell, NOS? Or do we use chart 1 to identify specific subtypes? For this case, using chart 1, would we note that bronchioalveolar is a subtype of adenocarcinoma and count this case as a single primary? Most of the MP/H rules schemas have a rule making an adenocarcinoma and a more specific type of adenocarcinoma a single primary. Would we apply rule M10 to this case and count it as a single primary? Or would we move on to rule M11 and count the case as two primaries?

After more than seven years, the patient in this case decided to proceed with the originally suggested standard therapy. Is this a multiple primary case because the tumors are "diagnosed" more than 3 years apart? Or should we assume this is further progression of the 2000 case because it was originally only treated with alternative therapies? The clinician in this case indicates the patient is being referred for treatment to the right upper lung originally diagnosed in 2000.