Extranodal Marginal Zone Lymphoma (ENMZL) of Mucosa-Associated Lymphoid Tissue (MALT) is a problematic and sometimes controversial diagnosis. While commonly seen in the stomach in the setting of chronic Helicobacter pylori infection, other extranodal sites, such as the lung, may also present with disease. ENMZL is clinically and morphologically heterogeneous; however, regardless of presentation, the etiology lies in the accumulation of lymphoid tissue in non-traditional sites. This phenomenon is typically secondary to an underlying inflammatory stimulus such as chronic infection or autoimmune states. The current case report details the clinical history of a patient with Sjögren syndrome over a four year period who eventually developed ENMZL. The patient initially presented with an atypical, but polyclonal, lymphoproliferative process diagnosed as lymphocytic interstitial pneumonia. Over time, the patient showed evolution to a monoclonal process with associated radiologic progression of disease. This evolution manifested as a dense lymphoid infiltrate with prominent plasmacytic differentiation and the development of a lung mass radiologically. This case contributes to the growing body of knowledge that suggests ENMZL lies along a biological spectrum of lymphoproliferative disorders whereby a benign, reactive process may eventually undergo malignant transformation. This evolution likely represents the acquisition of genetic abnormalities that allow autonomous proliferation in the absence of the initial immune stimulus. In practice, determining when this event occurs and, thus, distinguishing between reactive and neoplastic disorders within this spectrum may be difficult as no single clinicopathologic feature may be present to establish the diagnosis. This case further illustrates the importance of correlating the clinical, radiologic and pathologic data to evaluate patients with atypical pulmonary lymphoproliferative disorders and to allow the optimal management of their disease.
Primary osteoma cutis is a rare condition belonging to a spectrum of related genetic disorders, including progressive osseous heteroplasia, plate-like osteoma cutis, and Albright hereditary osteodystrophy, which share identical histologies with cutaneous intramembranous ossification and mutations in GNAS. We report a case of a 15-week-old girl who presented with an enlarging, indurated subcutaneous lesion on her right flank. CT scan showed an extensive subcutaneous sheet of calcification. Histologic evaluation revealed heterotopic calcification and intramembranous ossification within the dermis and mature bone largely replacing the subcutaneous fat compatible with osteoma cutis. Molecular testing was performed and identified an inactivating GNAS mutation. Unique to this case is a dermal proliferation of bland spindle cells that blended with deposited osteoid material. This has not been reported in association with primary osteoma cutis previously. These spindle cells were positive for CD44, Bcl-2, muscle-specific actin, and smooth muscle actin while negative for CD34. We hypothesize that these cells are immature mesenchymal cells, representing an early cellular phase of ossification. We favor these cells provide the background in which ossification is occurring, supporting the theory of osteoblastic metaplasia in the etiology of this condition.
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