Primary mandibular ALK-positive anaplastic large cell lymphoma in a 5-year-old child: a case report and review of the literature.

Anaplastic large cell lymphoma (ALCL) is a mature T-cell malignancy defined by the proliferation of large, pleomorphic tumor cells that express CD30 and the presence of characteristic hallmark cells. This entity is divided by ALK gene rearrangement into ALK-positive and ALK-negative subtypes with prognostic significance. ALK-positive ALCL typically affects children and young adults; primary oral and maxillofacial presentation is exceptionally rare and may mimic odontogenic or inflammatory disease. We report a 5-year-old boy with primary mandibular ALK-positive ALCL presenting as rapidly progressive swelling, with an ill-defined intraosseous lesion and cortical involvement on imaging. Histopathology revealed pleomorphic large lymphoid cells, including hallmark cells, with immunohistochemical expression of CD30, ALK, CD25, CD45, and perforin. Literature review disclosed male predominance and frequent mandibular involvement among reported oral cases. This is among the youngest reported cases of mandibular ALK-positive ALCL, underscoring the need for early biopsy and immunophenotyping for accurate diagnosis and management.