Re:What is generic basis and how the varying terms correlated please?
We thank Dr Naim for the interest in our paper. In our review of histiocytoid breast carcinoma (1), we have indicated that it is best categorized as a subtype of invasive lobular carcinoma, and this is stated in our title. The various terms mentioned in our review relate to historical descriptions that alluded to this unusual tumour, based on morphological evaluation and reports by authors who investigated this subject (2-6). The 'apocrine lobular' prefix is perhaps the most morphologically and immunophenotypically accurate among the terms, as histiocytoid breast carcinoma has been shown to express apocrine differentiation fairly consistently, and its underlying lobular origin is mostly well accepted. Eusebi et al used 'myoblastomatoid' to refer to its resemblance to granular cell tumour, which is a histologic differential diagnosis for histiocytoid breast carcinoma (6). The reference to 'pleomorphic' lobular breast carcinoma was because of the observation that histiocytoid carcinoma cells that mimicked 'foam' cells were noted in these aggressive pleomorphic tumours (2). While lipid-rich carcinoma was initially considered synonymous with histiocytoid breast cancer, lipid stains are generally negative in the latter (1, 3, 4). We are not suggesting that these myriad terms should be currently applied to histiocytoid lobular breast carcinoma. The purpose of their mention is to present a chronological sequence of how this entity was initially recognized and the subsequent work that led to our present understanding. We believe the term histiocytoid breast carcinoma is best applied to a tumour that consists of carcinoma cells that resemble benign histiocytes. Invariably, further workup usually establishes its lobular phenotype. 'Malignant histiocytoma', which implies a tumour of fibrohistiocytic origin, is not an appropriate term for histiocytoid lobular breast carcinoma which is epithelial and not fibrohistiocytic nature. When a breast tumour composed of histiocyte-like cells is established on immunohistochemistry to be epithelial in nature with lobular characteristics, the diagnosis of histiocytoid lobular breast carcinoma is firm. However, we acknowledge the potential challenges in making this diagnosis on needle core biopsy where limited sampling may pose diagnostic difficulty, and in such instances, further excision with more complete histological examination will allow a conclusive diagnosis. References 1.Tan PH, Harada O, Thike AA, Tse GM. Histiocytoid breast carcinoma: an enigmatic lobular entity. J Clin Pathol Mar 12.
2.Eusebi V, Magalhaes F, Azzopardi JG. Pleomorphic lobular carcinoma of the breast: an aggressive tumor showing apocrine differentiation. Hum Pathol 1992 Jun; 23(6): 655-62.
3.Hood CI, Font RL, Zimmerman LE. Metastatic mammary carcinoma in the eyelid with histiocytoid appearance. Cancer 1973 Apr; 31(4): 793-800.
4.Ramos CV, Taylor HB. Lipid-rich carcinoma of the breast. A clinicopathologic analysis of 13 examples. Cancer 1974 Mar; 33(3): 812-9.
5.Eusebi V, Betts C, Haagensen DE, Jr., et al. Apocrine differentiation in lobular carcinoma of the breast: a morphologic, immunologic, and ultrastructural study. Hum Pathol 1984 Feb; 15(2): 134- 40.
6.Eusebi V, Foschini MP, Bussolati G, Rosen PP. Myoblastomatoid (histiocytoid) carcinoma of the breast. A type of apocrine carcinoma. Am J Surg Pathol 1995 May; 19(5): 553-62.
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