Abstract
Communication between pathologists and clinicians is of the utmost importance for an adequate interpretation of histopathological findings.
In early 2018, we started to observe, in breast cancer specimens of patients submitted to neoadjuvant treatment or with small or mammographic detected lesions, an unusual pathological finding. It consisted of pseudocystic lesions, lined by epithelioid histiocytes and multinucleate foreign body giant cells (Figure 1). The pseudocyst contained a basophilic substance, resembling mucinous material. The wall had minimal fibrosis and histiocytic infiltrate, sometimes with abundant hemosiderin pigment (Figure 1). It was common to find such lesions in close proximity to neoplastic lesions (carcinoma in situ, invasive carcinoma) or lymph nodes (Figure 2). Due to these unusual findings, we discussed with a surgeon of our multidisciplinary team what type of material was being used, that could be related to those alterations. Together, and after literature research, 1 we came to the conclusion that such pseudocysts corresponded to a foreign body reaction to hydrogel-based, detectable breast biopsy markers. The histological pseudomucinous content, observed within the pseudocysts, correlates to the hydrogel component.
Low-power view of a pseudocystic lesion that has a thin fibrous wall (a) and is lined by epithelioid histiocytes, resembling a pseudosynovial reaction, and numerous multinucleated foreign body giant cells (b; arrowheads). Note the pseudomucinous appearance of the pseudocyst content and the presence of abundant siderophages in the cystic wall (b).
Pseudocystic lesions found in close proximity to neoplastic lesions: carcinoma in situ (a [arrows] and b) associated with a pseudocyst with basophilic, pseudomucinous content (a), invasive carcinoma of no special type (c, d), and a lymph node metastasis with evidence of tumor regression (e, f).
These sonographically detectable devices, used to mark the lesion(s) for resection, have been recently introduced at our hospital. They are composed of a biodegradable hydrogel polymer and a central permanent metal marker, which accurately mark the breast lesion (HydroMark 2 ; Figure 3). The very small dimension of the device might be the reason for the failure of macroscopic detection in most cases.
The pseudocystic lesions (a) corresponded to a foreign body reaction to sonographically detectable clips (b; arrowhead). Note the numerous multinucleated foreign body giant cells lining the cystic wall (a inset; arrowheads).
