Ran into a single patient who was diagnosed with this while I was doing my surgical rotation.
My preceptor (general surgeon of 30 years) and I were both entirely unfamiliar with it until when we received the biopsy results.
I will paste the UpToDate summary of the topic below:
SUMMARY AND RECOMMENDATIONS
●Castleman disease (CD) describes a heterogeneous group of lymphoproliferative disorders that share common histopathologic features and abnormal proliferation of morphologically benign lymphocytes. CD is classified based on the number of lymph node regions with enlarged lymph nodes. Unicentric CD (UCD) involves one or more lymph node(s) in a single region, while multicentric CD (MCD) involves multiple lymph node sites and is subclassified into human herpesvirus 8 (HHV-8)-associated MCD and HHV-8-negative/idiopathic MCD.
●UCD is most often an isolated lymphoproliferative disorder of young adults. Patients are commonly asymptomatic and are brought to clinical attention when an enlarged lymph node is noted on physical examination or imaging studies. Most lesions are in the mediastinum, but UCD can present in any lymph node location. Laboratory and clinical abnormalities are seen in less than 25 percent of cases. (See 'Signs and symptoms' above.)
●UCD should be suspected in the setting of a single persistently enlarged lymph node associated with moderate to intense post-contrast enhancement on computed tomography (CT). 18F-fluorodeoxyglucose positron emission tomography (FDG PET) should establish that the disease is limited to a single site. (See 'Imaging' above.)
●The diagnosis is made upon pathologic review of a biopsy of involved tissue, typically an excisional biopsy of a lymph node. Biopsy should demonstrate histopathologic features consistent with the hyaline vascular, plasma cell, or mixed histopathologic subtypes, though the clinical utility of these histopathologic subtypes is unclear. HHV-8 testing via LANA-1 should be performed and be negative in all cases of UCD. (See 'Pathology' above.)
●The evaluation should exclude other disorders that can present with a solitary enlarged lymph node that displays CD-like histopathologic features. (See 'Differential diagnosis' above.)
●For most patients, we recommend complete excisional resection of the involved lymph node rather than core biopsy or incomplete resection (algorithm 1) (Grade 1C). Complete resection is curative in the majority of patients. If the involved lymph node cannot be completely removed because of its anatomic location, we proceed with systemic therapy to reduce mass size followed by surgical resection. Options for systemic therapy include treatments utilized for HHV-8-negative/idiopathic MCD. Localized radiation therapy has a relatively limited role. (See 'Treatment' above and "HHV-8-negative/idiopathic multicentric Castleman disease", section on 'Classes of therapies'.)
●After resection, patients should be evaluated to determine the disease response to treatment and should be followed longitudinally for relapse and complications. Follow-up generally includes annual imaging and laboratory studies