Histopathologic examination showed compact orthokeratosis and granulomatous infiltrates with lymphocytes, histiocytic cells, epithelioid cells, and Langhans giant cells in the dermis. There were small areas of caseous necrosis. Periodic acid–Schiff stain demonstrated no fungal elements, and Ziehl-Neelsen stain showed no acid-fast bacilli. An intracutaneous test with purified protein derivative of tuberculin was performed. At 48 and 72 hours, a positive reaction was seen.
Detailed questioning of the patient revealed that he was in possession of a tropical fish aquarium, in which he used to immerse his hands. Moreover, he remembered that, 2 weeks before the appearance of the skin lesion on the finger, 1 of his fish (Procostomus type) died.
Verrucous Nodule of the Finger. Arch Dermatol. 1998;134(3):365-370. doi: