Mucocele-like Lesion: To Excise or Not to Excise?

Abstract Introduction/Objective Mucocele-like lesions (MLLs) are characterized by cystically dilated, mucin-filled ducts, usually associated with rupture and extravasation of mucin into the stroma. The epithelium lining the ducts may be attenuated or show a spectrum of proliferative changes ranging from hyperplasia to atypical hyperplasia to ductal carcinoma in situ (DCIS). Our study aims to evaluate the necessity of excision of pure MLL without atypia diagnosed on core needle biopsy (CNB). Methods/Case Report We retrospectively identified all subsequent in-house CNBs obtained between January 2017- August 2022 with MLLs. We reviewed all CNB slides with the diagnosis containing a “mucocele-like lesion” and assessed radiologic-pathologic concordance. An upgrade was defined as invasive carcinoma and/or DCIS in the excision. The excision slides of all upgraded cases were re-reviewed. Out of ~16000 consecutive CNBs in the study period, 69 CNBs from 69 patients yielded MLL alone, MLL with atypia, or MLL with carcinoma. We excluded 43 CNBs (7 patients with prior/concurrent carcinoma and 36 without excision). The final cohort consisted of 25 CNBs (14 with pure mucocele-like lesions and 11 MLLs with atypia). The CNB targeted mammographic calcifications in 42 cases, and 4 sonographic mass. Results (if a Case Study enter NA) Subsequent excision or clinical follow-up was available for 14 pure MLLs—of which one was upgraded. Five excisions showed atypia (4 atypical ductal hyperplasias (ADH) and one atypical lobular hyperplasia (ALH)). Excisions of 11 MLL with atypia yielded 1 case upgraded to DCIS (9.09%, 1/11) and seven excisions showed atypia (5 ADH, 1 ALH, and 1 flat epithelial atypia). DCIS in an upgraded case was in an area with biopsy site changes. There was no upgrade to invasive carcinoma in either group. Among the 36 MLLs excluded from the study due to not having excision available for review, twelve were followed up with interval radiology and showed either stable lesions or no residual calcifications. Conclusion There was one case with upgrade of pure MLLs in our series. Clinicoradiological surveillance can be considered in a patient without prior/current carcinoma in pathological-radiological concordant CNB diagnosis of pure MLL.