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Diagnosis and Discussion: Case 1138

Diagnosis

Mixed carcinoma in situ: Pleomorphic lobular carcinoma in situ (P-LCIS), with ductal carcinoma in situ (DCIS), nuclear grade 2-3, cribriform type with apocrine differentiation, comedonecrosis, and calcifications.

Discussion

Lobular carcinoma in situ (LCIS) is a non-invasive neoplastic proliferation of dyscohesive cells, originating in the terminal duct lobular units (TDLUs) [1]. The hallmark molecular alteration of these lesions is CDH1 inactivation, which leads to loss or impaired function of E-cadherin and subsequent dyscohesion of cells [2-3]. Classic LCIS is considered as a non-obligate precursor lesion, as well as a marker of generalized increase in risk of breast carcinoma [1, 4-5]. The current consensus for management involves increased surveillance in cases that are radiology-pathology concordant. On the contrary, variant LCIS, which includes pleomorphic and florid LCIS, have historically shown significantly higher upgrade rates upon excision (20-50%), and thus, the recommendation for management includes surgical excision [6-7]. This case demonstrates a unique combination of findings with not only pleomorphic LCIS, but also ductal carcinoma in situ (DCIS) admixed within this proliferation. The E-cadherin showed variably reduced membranous staining in LCIS, which is considered an aberrant pattern of expression. The E-cadherin in this case aided in distinguishing cells of lobular phenotype from those of ductal phenotype which comparatively showed strong membranous staining. This case illustrates the need to approach breast pathology with careful attention to detail and consider either multiple diagnoses or the possibility of a mixed population within the same lesion.

References

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