Discussion
Castleman Disease (CD) is a rare non malignant lymphoproliferative
disorder of uncertain etiology, first reported by Benjamin Franklin in
1954.1 It is also known as giant lymph node (LN)
hyperplasia or angiofollicular hyperplasia. Although it can present at
any age, its peak incidence is in 3rd and 4th decade.4
It can be classified clinically (on the basis of location) into two
types: Unicentric CD (localised disease) and multricentric CD (diffuse
or systemic disease). Histopathologically, CD is of two types: hyaline
vascular variant (HVV) and plasma cell variant (PCV). UCD is more common
(68-98%) than MCD. Further, majority of UCD are HVV, whereas majority
of MCD are PCV.4,5
UCD is usually an asymptomatic disease detected incidentally whereas MCD
often presents with constitutional symptoms (fever, night sweats, weight
loss etc). However, occasionally UCD may present with features of mass
effect on adjacent on adjacent organs such as cough, dysphagia, dyspnoea
or pain.6
Although CD can arise at any site where lymph node tissue is present,
but its most common site is in the thorax (70%). Other sites are
abdomen and pelvis (10-15%), neck (10-15%). In the thorax, most common
site of CD is the mediastinum. Other intrathoracic sites of UCD are the
hilum of lung, pleura, and chest wall.7
Identifying Castleman disease preoperatively is difficult. In the
present case, a well-defined posterior mediastinal mass was incidentally
detected on CECT chest in an asymptomatic 53-year old female which on
preoperative biopsy on histopathology was considered as an inflammatory
myofibroblastic tumour. Intra-operatively, the appearance was like that
of a malignant tumour. Preoperative contrast imaging (CT/ MRI) may help
to differentiate CD from other more common posterior mediastinal masses
(neurogenic tumours e.g. schwannoma, neurofibroma, ganglioneuroma). On
imaging, CD presents as a well-defined, homogeneous mass; however, the
characteristic feature of UCD on CECT is the intense enhancement
during arterial phase which decreases during portal venous phase. This
intense enhancement is due to hypervascular nature of localised CD
(UCD). Hence, multiphase CECT may be performed as the
investigation of choice if UCD is suspected.8 Further
CT may reveal relation of mass to adjacent organs and major vessels of
thorax, helping in surgical planning.
Identifying or suspecting UCD preoperatively may be useful for surgical
planning. Localised/Unicentric CD (UCD) is amenable to complete surgical
resection which is curative. However, UCD is known to be hypervascular
and have dense adhesions with adjacent organs or major
vessels2 which may pose a surgical challenge. In such
cases, either preoperative embolisation may be done (to reduce
vascularity) 9 or mass may be excised on
cardiopulmonary bypass (CPB) if dense adhesions with major vessels is
present.10 Video-assisted thoracoscopy (VATS) may be
associated with less postoperative pain and less hospital stay; however,
due to dense adhesions and vascular nature of CD, VATS does not appear
to be a lucrative option in CD.10
Prognosis of UCD is good as it behaves as a benign disease and
recurrence is rare; hence complete surgical resection is curative. On
the other hand, MCD can present as an aggressive lymphoproliferative
disease and debulking surgery and/or immunochemotherapy are treatment
options in such cases.7
In conclusion, UCD is a rare cause of intrathoracic mass, the etiology
and pathogenesis of which is unclear. It mimics both benign as well as
malignant lesions in the neck, thorax and abdomen. A high index of
clinical suspicion followed by focused evaluation with multiphase CECT
chest can help to establish its diagnosis preoperatively. Resection of
UCD may be difficult owing to hypervascularity and dense adhesions.
Hence, preoperative presumptive diagnosis of CD may help in proper
preoperative optimisation (embolisation), deciding surgical approach
(open thoracotomy vs VATS vs need for CPB).