Cutaneous Kikuchi Disease with Atypical Lymphomatoid Features

Final Diagnosis: Cutaneous Kikuchi's Disease/Cutaneous Kikuchi's Disease-Like Inflammatory Pattern with Atypical Lymphomatoid Features

Diagnosis Comment: The question is whether or not this lymphomatoid process reflects an evolving endogenous T-cell dyscrasia potentially arising in this Kikuchi's-like inflammatory pattern or if the lymphomatoid aspect of the infiltrate at this point in the patient's clinical evolution is a reactive process in the setting of the patient's Kikuchi's disease-like inflammatory pattern. There is, in fact, literature precedent regarding significant lymphoid atypia occuring in Kikuchi's disease where it can be confused with lymphoma. These cases bear a striking resemblance to a T-cell lymphoma because of the proliferation of large transformed cells with a high proliferation index, and as well CD5 was decreased in 40% of the cases. In conclusion, large T-cell proliferations can be alarming and are part of the histopathology of Kikuchi's disease. This type of lymphomatoid response is not uncommon in the spectrum of unusual autoinflammatory and autoimmune diseases.

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$Slide 1: The patient is a 50-year-old female who has a two-year history of ulcerated plaques on her face and other parts of the body. She has had multiple biopsies without a clear-cut diagnosis. The rash has proven to be refractory to treatment.$

Slide 2: There is a distinct pattern of cytotoxic interface dermatitis characterized by lymphocyte tagging along the dermal-epidermal junction and lymphocyte satellitosis around injured keratinocytes. The interface pattern is also associated with a significant degree of upward migration of lymphocytes into the mid and superficial layers of the epidermis.

Slide 3: There is a concomitant subjacent, fairly dense, lymphocytic and histiocytic infiltrate juxtaposed to blood vessels and adnexal structures.

Slide 4: The infiltrate is necrotizing in areas.

Slide 5: A noteworthy feature is the distinct cytomorphology of many of the histiocytes namely mononuclear cells exhibiting serpiginous and crescent-shaped irregular nuclear outlines.

Slide 6: There is an accompanying striking karyorrhectic debris.

Slide 7: While the lymphocytes within the epidermis are small and there are a number of smaller lymphocytes with admixed serpiginous and C shaped histiocytic elements in the dermis, there are many atypical larger transformed cells, hence defining this process as one showing atypical lymphomatoid features. The lymphomatoid aspect of this infiltrate, however, is noteworthy for the focality and the fact that the background infiltrate is not as atypical.

Slide 8: While the lymphocytes within the epidermis are small and there are a number of smaller lymphocytes with admixed serpiginous and C shaped histiocytic elements in the dermis, there are many atypical larger transformed cells, hence defining this process as one showing atypical lymphomatoid features. The lymphomatoid aspect of this infiltrate, however, is noteworthy for the focality and the fact that the background infiltrate is not as atypical.