Castleman disease of the subcutis and underlying skeletal muscle: report of 6 cases.

Castleman disease of the subcutis and skeletal muscle is rare. We have collected a series of 6 cases of extranodal Castleman disease, located in the subcutis and skeletal muscles of the extremities and trunk. Tumors from mediastinal and retroperitoneal soft tissue and those histologically involving peripheral or truncal lymph nodes were excluded. There were four females and two males; ages ranged from 18 to 37 years (mean, 26 years). Locations included thigh (n = 3), anterior chest (n = 2), and upper arm (n = 1). Sizes ranged from 4.0 to 6.0 cm (mean, 5.2 cm). All patients presented with localized disease. One patient had involvement of the mediastinum 1 year prior to the appearance of his soft tissue lesion. None of the patients demonstrated systemic involvement or signs of the POEMS syndrome. Histopathologically, all cases were classified as hyaline-vascular type (HVCD). In 3 cases, follicular dendritic cell dysplasia was observed. In 1 case, the dysplasia was marked. The subcutaneous lesion of 1 patient revealed a maze of capillaries set in a lipomatous background with occasional lymphoid follicles possessing hyalinized lymphocyte-depleted centers. This lesion probably represented incipient HVCD. Molecular biologic studies did not reveal the presence of Epstein-Barr virus or human herpesvirus-8 DNA in the lesional tissue. There also were no monoclonal rearrangements of IgH. Four patients with follow-up included 2 patients with no evidence of disease at 10 and 13 years, respectively, and 2 patients with local recurrence at 2 and 6 months, respectively. In conclusion, soft tissue Castleman disease is a disease of young patients with a female predominance and a propensity to involve the trunk and limbs. It can be of large size and is generally solitary. There may be mild to marked follicular dendritic cell dysplasia. The HVCD predominates in this location. These lesions are usually unassociated with POEMS, Epstein-Barr virus, human herpesvirus-8, or monoclonal rearrangements of IgH.