Oral Lymphomatoid papulosis type C: A diagnostic pitfall, often confused with T-cell lymphoma

- Oral LyP is a benign, self-resolving disease with similar morphology to cutaneous LyP.
- Biopsies of type C oral LyP are commonly misinterpreted to be aggressive peripheral T-cell lymphoma.
- Recognition of oral LyP is critical to avoid the toxic treatments intended for high grade lymphoma.

Eosinophilic ulcer of the oral mucosa (EUOM) is a rare, benign, self-resolving lymphoproliferative disorder, which typically presents with asymptomatic to mildly tender ulcers. Histological findings of EUOM are characterized by a polymorphic infiltrate with many eosinophils often extending into the underlying muscle. Although this entity is well documented within the dental literature, it is not well known to physicians. The pathogenesis of the condition is unclear, although reports dating back to 1997 suggest that at least a subset of EUOM represents CD30 positive lymphoproliferative disorder (CD30 + LPD). More specifically the original report and subsequent authors suggest that the patients fall on the spectrum of CD30 + LPD most reminiscent of Lymphomatoid papulosis (LyP) seen in the skin. This oral variant of LyP would be expected to have the same diverse morphologic spectrum as that seen in cutaneous LyP. We present five EUOM patients whose biopsies showed an atypical lymphocytic infiltrate most compatible with Type C LyP, a histologically unique subset of LyP, reminiscent of the biopsy findings encountered in the reported case by Ficarra and co-workers. (Ficarra, et al., 1997) In four of the five cases, the biopsies were interpreted by expert hematopathologists as an aggressive form of peripheral T cell lymphoma resulting in recommendations to administer systemic chemotherapy to four of the patients, the scheduling of one patient for induction therapy and transplantation before revision of the diagnosis, and administration of chemotherapy to one of the patients. The natural clinical course of spontaneous regression refuted the original diagnoses as a form of aggressive peripheral T cell lymphoma. Recognition of oral LyP is critical to avoid inadvertent exposure to potentially toxic chemotherapeutic regimens intended for the treatment of high grade lymphoma.