Cutaneous mantle cell lymphoma histomorphologically mimicking subcutaneous panniculitis‐like T‐cell lymphoma: Case report

Abstract

Secondary cutaneous involvement by mantle cell lymphoma (MCL), an uncommon aggressive B-cell malignancy, predominantly involves the dermis, with few reports of pannicular involvement. Lymphocytic infiltration of subcutaneous tissue is associated with /journal/cup J Cutan Pathol. 2019;46:538-541.sone, and rituximab or a rituximab-bendamustine induction therapy, followed by maintenance rituximab. 14 While cutaneous lesions may be the initial site of clinical detection of disease, 3 primary (skin only) cutaneous MCL has not been convincingly documented in the literature and all patients presenting with cutaneous MCL warrant work-up for widespread disease. It is therefore imperative to differentiate cutaneous involvement of MCL from benign inflammatory conditions and other, more indolent, cutaneous lymphomas. MCL can promptly be distinguished through immunophenotyping, primarily with staining for cyclin D1 and SOX11. Further confirmation may be obtained with molecular genetics (CCND1/IgH fusion by FISH).Adipotropism by SPTCL is thought to reflect a unique interaction between CCL-5 positive lymphocytes and CCR5 positive adipocytes. 15 We postulate that the current case involves interaction between the unique microenvironment of adipose tissue and neoplastic cells, leading to the preferential involvement of the infiltration into the adipose tissue.Of the genetic alternations identified through sequencing our patient's tumor cells, it is interesting that mTOR is implicated in adipogenesis, adipocyte maturation, adipocyte terminal differentiation, as well as key roles in regulating endocrine functions of adipose tissue. 16 Alterations in mTOR are not specific to MCL and mutations are implicated in many other types of lymphomas and neoplasms. 17 The complex and central role that mTOR plays in adipose homeostasis may link our tumor to its preference to the adipose tissue, although further investigation is warranted regarding specific genomic alterations in lymphomas and the implications these mutations have in the involvement of tumor cells with cutaneous and adipose environments. While morphologic features of SPTCL, specifically rimming of adipocytes by neoplastic lymphoid cells, have been documented in other type of lymphomas, this case is exceptional in that the morphologic features of SPTCL are showed in secondary cutaneous involvement by MCL. The rare panniculitis-like presentation of aggressive B-cell lymphomas represents a potential pitfall for pathologists anddermatopathologists. This case supports the common practice of routinely using specific immunohistochemical staining, and/or molecular cytogenetics, for all cases of panniculitis-type lymphomas. Further research is warranted to describe the full spectrum of cutaneous Bcell lymphomas that present with panniculitis-like features. ORCIDCaroline Laggis https://orcid.org/0000-0003-3819-9345