Diagnostic Histopathological Findings on a Tick-Bite Lesion without the Presence of an Insect Body.

Tick bite is detected when the insect's body remains, and portions, such as the mouthparts, may be used to confirm the species and the potential for microbial infection. Moreover, a histopathological diagnostic standard for tick-borne illnesses has not yet been established. Thus, this study aimed to perform a histopathological examination of the lesion in a patient in whom a tick was not identified along with its bite. The patient was a 47-year-old man who presented with a lesion caused by a tick bite; the lesion was resected en bloc from the subcutaneous fat on the left side of the neck. Histopathological findings showed necrosis and thickening of the epidermis, ulceration, a strong periodic acid-Schiff stain-positive substance over the epidermis, extravascular exposure of erythrocytes in the dermis, thrombi, sclerosis of collagenous fibers, pseudolymphoma with a predominance of T cells, and marked infiltration of basophils extending from the epidermis to the subdermal sebaceous layer. Tick-bite lesions may be detected histopathologically, even if the presence of the insect body is not confirmed, as in this case, if the injection of tick saliva and local reaction of the salivary component are histologically evaluated.