Histiocytoid breast carcinoma: an enigmatic lobular entity

Abstract

Histiocytoid breast carcinoma is an uncommon entity that is mostly regarded as a variant of lobular carcinoma. Its occurrence with apocrine lobular carcinoma in situ and consistent expression of gross cystic disease fluid protein 15 suggest apocrine differentiation. Its recognition is often challenging, particularly when histiocytoid tumour cells occur in a metastatic site before the primary diagnosis of breast carcinoma, or in limited core biopsy or cytology material. In the breast, its bland histological appearances can lead to a benign diagnosis. Clues to the correct conclusion include finding tumour cells with more cytological atypia, the presence of cytoplasmic vacuoles and secretions, coexistence with more traditional invasive lobular carcinoma patterns and/or lobular neoplasia, and the use of immuohistochemistry to confirm their epithelial nature. Close clinicoradiological correlation and awareness of histological mimics are needed to achieve an accurate diagnosis of this enigmatic condition that should be appropriately subsumed within the invasive lobular histological subtype.

Periocular Histiocytoid Carcinoma: Potential Diagnostic Challenges

“…Unfortunately, molecular and immunohistochemical markers that clearly differentiate primary and metastatic tumors are not known. In both, the neoplastic cells are immunopositive for cytokeratins CK7, AE1/AE3, CAM 5.2, and EMA, whereas they are generally immunonegative for CK20 [2,24]. Positive immunoreactivity for GCDFP-15, carcinoembryonic antigen, and Ber-EP4 has also been reported [2,24].…”

“…In both, the neoplastic cells are immunopositive for cytokeratins CK7, AE1/AE3, CAM 5.2, and EMA, whereas they are generally immunonegative for CK20 [2,24]. Positive immunoreactivity for GCDFP-15, carcinoembryonic antigen, and Ber-EP4 has also been reported [2,24]. E-cadherin is immunopositive in around 80% of the primary periocular histiocytoid carcinoma cases, whereas immunoreactivity is seen in only 25% of the histiocytoid breast carcinomas cases [1-5, 20, 22, 28-34].…”

“…One case of histiocytoid carcinoma in the male breast has been reported [22]. The tumors are most commonly regarded as a variant of lobular carcinoma, and their occasional occurrence with apocrine lobular carcinoma in situ and expression of GCDFP-15 suggest apocrine differentiation [23,24]. Both lobular and histiocytoid breast cancers can metastasize to the periocular region, often with bilateral involvement [25,26].…”

Mesenchymal tumours of the breast and their mimics: a review with approach to diagnosis

“…The differential diagnosis based on the imaging appearances is often ruptured cysts and fat necrosis. [143][144][145] Pathology Histiocytoid carcinoma is characterised by bland epithelioid cells with abundant pale eosinophilic slightly granular to frothy cytoplasm variably arranged as sheets, single cells and cords infiltrating breast parenchyma. The low power appearance can be subtle, particularly in tumours showing a dispersed pattern.…”

“…6A). 145 Evaluation of metastatic sites may be particularly challenging; lymph node deposits may mimic sinus histiocytosis and cutaneous deposits may be confused with xanthogranuloma.…”