Utility of cryobiopsy for diagnosis of mucinous adenocarcinoma

[Background] Mucinous adenocarcinoma (MA) is a rare lung adenocarcinoma that is difficult to distinguish from pneumonitis on imaging. According to a recent classification, MA includes mucinous adenocarcinoma in situ, minimally invasive adenocarcinoma, and invasive mucinous adenocarcinoma. A definitive pathological diagnosis of MA is often difficult by transbronchial lung biopsy (TBLB) because of the small specimen. Transbronchial lung cryobiopsy (TBLC) provides a large biopsy specimen with less tissue damage. Thus, TBLC may be useful for diagnosis of MA, but its contribution has not been reported.[Methods] We reviewed 74 MA patients who underwent bronchoscopic biopsy from July 2011 to December 2023 at our institution (TBLC was introduced in 2018). To determine the usefulness of TBLC for diagnosis of MA, we examined the diagnosis rate for MA using this procedure and background characteristics.[Results] The patients had a median age of 74 years (42–89) and 64% were men (47/74). The diagnosis rate for TBLB was 45.8% (27/59), whereas that for TBLC was 100% (15/15). Of the 10 patients who were not diagnosed on the first biopsy and required a second biopsy, three underwent TBLC with a diagnosis rate of 100% (3/3), and seven underwent TBLB with a diagnosis rate of only 57.1% (4/7). The three patients without a diagnosis on the second TBLB were confirmed by TBLC. Thus, all 21 patients who underwent TBLC had a diagnosis rate of 100%. Although TBLC was a significant factor for diagnosis (100% vs. 45.8%, p<0.01), the patients’ background characteristics, such as tumor location, age, and imaging patterns, showed no associations in a logistic regression analysis. [Conclusions] TBLC is more useful than TBLB for diagnosis of MA.