Infantile digital fibroma is a rare benign lesion that usually occurs during the first 2 years of life. It can be multiple, but it is usually a single lesion. If it grows large enough it can cause joint deformities or interfere with everyday activities. Microscopically, the neoplastic cells usually have inclusion bodies that are best highlighted with a Masson trichrome stain but can often be seen on hematoxylin-eosin staining. Treatment for this entity is usually watchful waiting because of its ability to spontaneously regress, but excision is recommended if the lesion is symptomatic. More recently, fluorouracil or injectable steroids have shown great promise in inducing regression without the complications that accompany surgery.

Duodenal-type follicular lymphoma (D-FL) is a newly recognized entity in the 2016 World Health Organization classification update. It has an immunophenotype similar to that of other FLs and usually carries the typical t(14;18)(q32;q21) translocation. However, unlike other FLs, D-FL is almost always diagnosed at a low stage and stays localized to the small intestine, most commonly the second portion of the duodenum, whereas the vast majority of other FLs are diagnosed at an advanced stage. Additionally, D-FL gene expression and pathogenesis appear to be more closely related to extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue than to other types of FL. Therefore, many oncologists have opted to treat this variant of FL in a "watch and wait" manner because of its excellent prognosis and the rarity of D-FL to progress even when no treatments are attempted.

A 19-year-old Caucasian female with adult-onset Still disease (AOSD) presented for evaluation of an acute clinical decompensation and atypical annular papules and plaques with purpura on the lower extremities. A punch biopsy demonstrated histiocytes with engulfed degenerated erythrocytes and lymphocytes, consistent with hemophagocytic lymphohistiocytosis (HLH). HLH, clinically referred to as macrophage activation syndrome, is a rare complication of AOSD and is life-threatening.Relevant clinical, laboratory, and histologic features of this diagnosis are reviewed. K E Y W O R D Sadult-onset Still disease, canakinumab, hemophagocytic lymphohistiocytosis, histopathology, macrophage activation syndrome, skin biopsy, tacrolimus

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