[Unusual gluteal localization of unicentric Castleman's disease: A case report and review of the literature]

BACKGROUND

Castleman's disease is a rare and benign lymphoproliferative disorder which can be unicentric (UCD) or multicentric (MCD). UCD usually involves a single lymph node or less frequently a group of lymph nodes. The most common sites of nodal UCD presentation are the mediastinum, neck, abdomen and retroperitoneum. Rarely extranodal involvement has been reported. The intramuscular location is very unusual with only about 10 cases described in medical literature so far.

CASE REPORT

We present a case of atypical localization of Castleman's disease occurring in the right gluteal area in a 40-years-old female patient. The patient was asymptomatic and clinical examination was unremarkable except for a right gluteal palpable mass. The CT scanner-guided needle core biopsy was inconclusive. A surgical excision was then performed that revealed a hyaline-vascular type of Castleman's disease. The patient has an uneventful post-operative course.

CONCLUSION

The present case is instructive in the work-up of primary soft tissue tumors, for which Castleman's disease is extremely rare and not considered in the differential diagnosis of clinicians. Pathologists must be aware of its existence so that it can be evoked in the presence of a lymphoid population on histological examination.

[Castleman disease]

The term "Castleman disease" covers a variety of entities that have very different clinical, biological, pathological and physiopathological features. In this issue, we review the characteristics of the unicentric Castleman disease, of the HHV8 associated multicentric Castleman disease and the idiopathic multicentric Castleman disease associated or not with TAFRO syndrome ("thrombocytopenia, anasarca, fever, reticulin myelofibrosis and/or renal insufficiency, organomegaly"). We detail the differential diagnostics of these entities.

La maladie de Castleman : aspects anatomopathologiques

Histologically, Castleman's disease associates three subtypes: 1-the vascular hyaline (HV) subtype more often seen in unicentric forms; 2-the plasmacytic (PV) subtype, more frequently associated with the HHV8+ and idiopathic multicentric form; 3-the mixed subtype associating both HV and PV aspects that may be encountered in any type of Castleman's disease. If the diagnosis of unicentric (isolated mass) and multicentric HHV8+ Castleman's disease is easy, the diagnosis of the idiopathic multicentric form remains particularly difficult because it is at the crossroads of many other pathologies (infectious, tumoral and dysimmune), making an anatomoclinical comparison necessary. The role of the pathologist, in the context of disseminated lesions (polyadenopathy and splenomegaly), is to identify lesions that may be part of Castleman's disease, to systematically perform HHV8 testing and to perform complete phenotyping associated with molecular analysis (B and T-cell clonality) in order to rule out a lymphomatous process and certain infectious etilogies. In all cases, its role will be a warning bell and the diagnosis of Castleman's disease will be retained only after a rigorous anatomic and clinical confrontation. © 2022 Published by Elsevier Masson SAS on behalf of Société nationale française de médecine interne (SNFMI).