Intracystic Papillary Carcinomas of the Breast Are More Similar to In Situ Carcinomas Than to Invasive Carcinoma

Abstract

To the Editor: We read with interest the article by Wynveen et al4 regarding intracystic papillary carcinoma (IPC). In this article Wynveen et al4 describe a clinical pathologic study of 13 cases of pure IPC, 8 cases of IPC with or indeterminate for microinvasion (IPC±microinvasion), and 19 cases of IPC associated with invasion. The results of their study are generally similar to other studies carried out earlier on the subject1–3; however, inclusion of cases with microinvasion and obvious invasive carcinoma associated with IPC made it difficult to tease out the clinical follow-up data on pure IPC, resulting in a somewhat erroneous conclusion. The authors have concluded that IPC constitutes a spectrum of intraductal and invasive carcinoma, with predominance of the latter.4 We disagree and would rather conclude that IPC is associated with a spectrum of intraductal and invasive carcinoma, but pure IPC is morphologically and clinically more similar to intraductal carcinoma. Our conclusion is not based solely on collagen IV staining (which can vary from 1 laboratory to another because of a variety of reasons)2; it is also based on clinical follow-up data provided by our previously published report2 and on the current study by Wynveen et al.4 Of the 13 cases of pure IPC in this study, 3 underwent lymph node sampling at diagnosis. All 3 cases had negative lymph node status. On follow-up, none of these 13 cases developed axillary recurrence. However, local inbreast recurrence was identified in 3 cases. Of these 3 patients, 1 recurred as pure IPC within 2 years and subsequently developed ipsilateral invasive lobular carcinoma. Another patient recurred as pure IPC 8 years after diagnosis, which was excised. This patient was reported to develop bone metastases 9 years later. However, no information was provided regarding the morphology of the metastases or whether the excised tissue was entirely submitted for histologic evaluation to exclude any concurrent invasive carcinoma. The third patient recurred as invasive ductal carcinoma 8 years after diagnosis. Recurrence can occur and is not uncommon in patients with a diagnosis of in situ carcinoma. In situ carcinoma is also associated with increased risk of developing an invasive malignancy in the breast. The development of bone metastases is clearly a feature of invasive carcinoma; however, lack of information on specimen processing on the only pure IPC case with metastases in this study raises the possibility of an unsampled invasive carcinoma in the specimen. On the basis of this study and on other previously carried out studies, IPCs (also known as encysted or encapsulated papillary carcinomas) are circumscribed papillary tumors that often lack myoepithelial cell markers on immunohistochemical examination.1–4 However, in absence of frank invasion their clinical behavior is similar to that of ductal carcinoma in situ. The most challenging part of processing breast specimens with IPC is a thorough histologic evaluation of the entire specimen. Although all excisional biopsies and lumpectomies can be entirely submitted for histologic evaluation, this task cannot be practically accomplished in a mastectomy specimen. In the latter case, the pathologist can extensively sample the tissue in the immediate vicinity of IPC and carry out a thorough gross evaluation of the remainder of the mastectomy specimen to exclude the possibility of invasion. We do agree with Wynveen et al4 that appropriate management of patients with a core biopsy diagnosis of IPC is the carrying out of a lumpectomy with sentinel lymph node mapping. However, our reasoning is different. Sentinel lymph node mapping should be offered to these patients not because pure IPC is a form of invasive carcinoma but because they have a high likelihood of harboring an invasive tumor in the immediate vicinity. From a conceptual standpoint, it is reasonable to believe that IPC represents a lesion somewhere in between in situ carcinoma and invasive carcinoma; however, clinically, these lesions are more close to in situ carcinoma and should be managed similar to mass forming ductal carcinoma in situ. Rohit Bhargava MD *Magee-Womens Hospital of UPMC Pittsburgh, PA Nicole N. Esposito MD †H. Lee Moffitt Cancer Center Tampa, FL David J. Dabbs MD *Magee-Womens Hospital of UPMC Pittsburgh, PA