Carcinoma Erysipeloides From Metastatic Cutaneous Squamous Cell Carcinoma Initially Mistaken for Intralymphatic Histiocytosis.

Intralymphatic histiocytosis is a rare dermatologic disorder, commonly associated with inflammatory disorders and rarely malignancy. Carcinoma erysipeloides (CE) is a rare pseudoinflammatory cutaneous eruption that resembles soft -tissue infections as result of intralymphatic metastasis and subsequent lymphatic obstruction. Breast carcinoma represents most of the CE cases, but rarely other malignancies are involved. This report discusses a patient with a history of cutaneous squamous cell carcinoma (SCC) of the temple, who was initially diagnosed with intralymphatic histiocytosis located on his upper extremity, resistant to treatment. Further dermatologic and pathologic review later revealed metastatic SCC restricted to the dermal lymphatics, creating a CE reaction, initially obscured by intralymphatic histiocytes. This case highlights the difficulty in diagnosing metastatic carcinoma when the malignant cells are accompanied by a dense histiocytic infiltrate. The case demonstrates a rare presentation of CE due to metastatic cutaneous SCC and highlights the need for persistent investigation when confronted with nonconforming pathology.