Cutaneous B-cell pseudolymphoma (CBPL) may appear in the face, chest, or upper limbs, and it can be asymptomatic or in the form of nodules, papules, or masses. In most cases, it is idiopathic. However, some causes that have been identified are trauma, contact dermatitis, injected vaccinations, bacterial infections, tattoo dyes, insect bites, and certain drugs. Since the histology and clinical presentation of cutaneous pseudolymphoma (CPSL) are similar to those of cutaneous lymphomas, the diagnosis is usually based on an incisional or excisional biopsy. In this paper, a 14-year-old male patient with a two-month-old mass in the right lateral thoracic region is taken as a case study. He had neither symptoms, nor a past medical history, nor a family history. He had an insect bite a month ago and was fully vaccinated. However, the mass was some centimeters away from the insect bite. A biopsy was taken. The products of it were two paraffin cubes and two histological slides (H&E). The diagnosis was cutaneous B-cell pseudolymphoma. The total removal of the mass was decided since, in idiopathic cases like this, CBPL is not usually healed with topical and non-invasive treatments. Follow-up examinations were suggested since a further antigenic reaction is possible. If cutaneous B-pseudolymphoma is early diagnosed and treated, it does not cause serious problems. In some cases, it even resolves on its own.