Atypical squamous metaplasia of seromas in breast needle aspirates from irradiated lumpectomy sites: A potential pitfall for false‐positive diagnoses of carcinoma

Abstract

The presence of squamous metaplasic cells is an uncommon finding in fine-needle aspiration (FNA) biopsies of the breast. We report that FNA smears containing atypical squamous metaplastic cells derived from the lining of seroma-type cavities following lumpectomy and irradiation in patients with breast cancer can be a potential pitfall for a false-positive diagnosis of recurrent malignancy. Four fine-needle breast aspirates from two adult patients with previous histories of invasive breast carcinoma were retrieved. One specimen was from a 56-yr-old female, while the remaining three FNAs aspirates were from a 75-yr-old female. Both patients presented with indurated cystic lesions arising at irradiated lumpectomy sites. The cytospins from the 56-yr-old patient showed markedly atypical cells having enlarged, degenerating, hyperchromatic nuclei and surrounding dense cytoplasm with sharp borders that were suspicious for carcinoma. A mastectomy revealed irradiation changes and atypical squamous metaplastic cells lining a cystic cavity consistent with a seroma, but there was no evidence of residual cancer. After three aspirations yielded "atypical" diagnoses, the second patient underwent core needle biopsies that also revealed changes consistent with a seroma cavity lined by atypical squamous metaplastic cells. We believe this is the first report of squamous metaplasia occurring in a seroma cavity following lumpectomy and irradiation of the breast. The squamous metaplastic cells in aspirates of these cystic lesions may display significant cellular atypia that can potentially result in a false-positive diagnosis of malignancy.

Fine-needle aspiration cytology of metaplastic carcinoma of the breast

“…30 31 Atypical squamous cells can be noted in the smears of seroma A B with post-irradiation atypia, 32 PT with intracanalicular metaplastic epithelial lining cells 33 34 and squamous cell carcinoma (metaplastic carcinoma). Therefore, the presence of atypical squamous cells in the aspirate may not necessarily indicate an underlying malignant lesion.…”

Fine Needle Aspiration Cytology of Seromas of the Breast from Irradiated Lumpectomy Sites

“…[1][2][3] In none of our cases did we find any atypical squamous metaplastic cells as a potential diagnostic pitfall, as described recently. 4 Also, while the findings of epithelial atypia with a high nuclear/ cytoplasmic ratio 4 may be regarded as a potential diagnostic pitfall for a false positive diagnosis, based on our study we do not consider them of serious consequence since in our cases we used cell blocks to yield reasonable histologic information to minimize the chance of such an error.…”

“…6 In these circumstances, FNAC as a first-line, noninvasive investigation may play an important role in the diagnosis of tumor recurrence and differentiation from benign changes, including atypia due to radiation, which is known to be a potential diagnostic pitfall for a false positive diagnosis of carcinoma. [1][2][3][4] In the cases in this study we had no difficulty diagnosing the 2 cases of recurrent carcinoma in cytologic preparations, and the cell blocks were of additional help in highlighting the histologic features of the malignant cells that were similar to those of the primary tumor. In 21 cases the cytologic preparations, along with the cell blocks, gave convincing information on the benign nature of the lesion, and in all these cases similar findings were noted on a follow-up aspiration, thus avoiding surgical biopsy.…”

“…In fine needle aspiration samples from a seroma with no unusual pathology, generally the findings are of a paucicellular sample with a few foam cells. 4 In 4 cases with highly atypical cells, a core biopsy was performed despite the fact that the atypical cells in cytologic samples on comparison did not resemble the primary breast carcinoma. In view of negative findings on the core biopsy, the atypias were regarded as due to the effects of radiation.…”

“…1,3 Also, a recent study emphasized the occurrence of atypical metaplastic squamous cells in seromas, which were considered a diagnostic pitfall for a false positive diagnosis. 4 Since local recurrence of carcinoma of the breast following surgical treatment is frequent, an early diagnosis is essential to permit timely management. In this regard, FNAC is a noninvasive, first-line investigation, and we have used it in seromas to determine if FNAC would be useful in the diagnosis of tumor recurrence and other atypia that may result in a diagnostic pitfall for a false positive diagnosis.…”