 Abstract | | |
Extranodal follicular dendritic cell sarcoma (ENFDCS) is a rare hematolymphoid tumor, masquerading as soft tissue sarcoma on initial histological examination. So, for its confirmation, the application of immunohistochemistry (IHC) is of paramount importance. Over the years there has been a major shift in the demography of follicular dendritic cell sarcoma (FDCS), with a rise in the number of extranodal cases. Herein we report a case of ENFDCS presenting as a rectal polyp, who had a history of intermittent bleeding per rectum and passage of fleshy mass while defecation. As these tumors share an overlapping morphology with other spindle cell tumors and can occur at unpredictable locations, they pose a diagnostic challenge, especially for young pathologists.
Keywords: Extra nodal, follicular dendritic cell sarcoma, inflammatory pseudotumor-like follicular/fibroblastic dendritic cell sarcoma, polyp, rectum
How to cite this article:
Gurung N, Mukherjee U, Khurana A. Extranodal Follicular dendritic cell sarcoma presenting as a rectal polyp: An entity overlooked by its differentials. Indian J Pathol Microbiol 2021;64:814-6 |
How to cite this URL:
Gurung N, Mukherjee U, Khurana A. Extranodal Follicular dendritic cell sarcoma presenting as a rectal polyp: An entity overlooked by its differentials. Indian J Pathol Microbiol [serial online] 2021 [cited 2021 Dec 7];64:814-6. Available from: https://www.ijpmonline.org/text.asp?2021/64/4/814/328555 |
| Introduction | |  |
FDCS is an enigmatic rare entity of follicular dendritic cell (FDC) histogenesis, first described by Monda et al. in 1986.[1] It can occur over a wide age range, with an adult predilection (median age being 50 years) and having an equal sex distribution.[2] FDCS have a greater affinity for extra nodal site presentation (58%), followed by lymph node (31%) and both in (10%) of the cases.[3] The precise pathogenesis of FDCS is not ascertained, however, a proportion of cases have arisen in the background of Castleman disease.[4] Rare cases of FDCS patients developing paraneoplastic pemphigus have been reported in the literature.[5]
| Case | | |
Our case is a 20-year-old male with the complaint of bleeding per rectum for 3 months duration and sudden passage of a fleshy mass while defecation. The spontaneously expelled mass was sent for pathological examination, which revealed a polypoidal tumor with intact surface epithelium. The tumor involved and replaced the lamina propria and muscularis propria, which comprised of a predominant population of polygonal to epithelioid cells arranged in nests and sheets [Figure 1]a. Focal areas revealed ovoid to spindle cells in fascicles and whorls [Figure 1]b.The former population of cells had moderate eosinophilic cytoplasm, eccentrically placed nuclei with prominent grooves and folds. The nuclei showed vesicular chromatin and conspicuous eosinophilic nucleoli. Rare mitosis was seen. Necrosis was absent.On IHC, the tumor cells were positive for vimentin along with follicular dendritic cell markers CD21 [Figure 2]a and CD23 [Figure 2]b.They are negative for panCK, CK18, epithelial membrane antigen (EMA), leucocyte common antigen (LCA), S-100, HMB-45, Melan-A, CD34, CD117, DOG-1, Desmin, CD1a, CD68, MPO, Synaptophysin, Chromogranin, CD31, CD138, and CD30. INI-1expression was retained.Ki-67 proliferative index was approximately 10%. Keeping in view of the observed histology and the overall immunophenotype a final diagnosis of an extra-nodal follicular dendritic cell sarcoma (ENFDCS) was rendered. On clinical assessment, per rectal examination was normal. Colonoscopy revealed a 4–5 cm polyp with thick short and wide stalk in the rectum. On CT-scan a large lobulated broad-based polypoidal mass was seen arising from the posterior wall of the mid rectum, which was protruding into the lumen. As the disease was radiologically and clinically limited to the rectum, surgery was opted as the preliminary treatment and for reconfirmation of the histopathology. The patient underwent abdominoperineal resection. On gross examination, the mass was polypoidal cauliflower-like growth [Figure 3] and was histopathologically identical to the former expelled mass. Regional lymph nodes were free of tumor. The circumferential radial margin along with the mucosal cut ends was free. | Figure 1: (a) The tumor cells are predominantly polygonal to epithelioid having moderate to abundant eosinophilic cytoplasm, eccentrically placed plasmacytoid nuclei. The nucleus demonstrates irregular prominent grooves and folds. (H and E x 400). (b) Focally the tumor comprises of spindled cells exhibiting a whorling appearance at places with scattered inflammatory cells in the background (H and E x 400)
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 | Figure 2: (a) The tumor cells are diffusely positive for CD21 (IHC x 400). (b) Tumor cells also show focal membranous CD23 expression (IHC x 400)
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 | Figure 3: On gross examination, a polypoidal cauliflower-like mass was seen arising from the posterior wall of rectum
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| Discussion | | |
FDCS are rare hematolymphoid tumors, which show proliferation of spindled to ovoid cells having morphologic and immunophenotypic features of FDCs. They should be positive for one or more of the FDC markers i.e., CD21, CD35, or CD23. CXCL13 and clusterin are very sensitive markers for FDSC as they are usually negative for other dendritic cell tumors.[6] They also express desmoplakin, vimentin, fascin, epidermal growth factor receptor (EGFR), and human leukocyte antigen – DR isotype (HLA-DR) with variable positivity for EMA, S-100, and CD68. FDC secreted protein, serglycin, and programmed cell death ligand 1 (PD-L) 1 expression have also been recently reported in FDSC.[7]
Conventionally, FDCS comprises of spindled to ovoid tumor cells characteristically arranged in fascicles, storiform, whorls, diffuse sheets, and vague nodules with slight infiltration by small lymphocytes. Therefore, at the extranodal locations, the diagnosis of ENFDCS is mostly missed amidst other common spindle cell tumors of the site. The tumor cells elicit bland cytology with vesicular chromatin, small conspicuous nucleoli, and frequent nuclear pseudo inclusions. Other morphological variations include epithelioid, clear, and oncocytic tumor cells, myxoid stroma, fluid-filled cystic spaces, and osteoclastic giant cells.[8],[9]
In our case the tumor was predominantly polygonal to epithelioid cells, so the initial differentials considered were malignant melanoma, epithelioid gastrointestinal stromal tumor, rhabdomyosarcoma, langerhans histiocytosis, anaplastic large cell lymphoma, and extrarenal rhabdoid tumor. An extended panel of IHC was run to exclude all of the above entities including CK, CK18, EMA, LCA, S-100, HMB-45, Melan-A, CD34, CD117, Discovered on GIST-1 (DOG-1), Desmin, CD1a, CD68, Myeloperoxidase (MPO), Synaptophysin, Chromogranin, CD31, CD138, CD30, and INI-1. However, the focal presence of ovoid tumor cells in whorls with sprinkled lymphocytes in the background was the main morphological catch, further confirmed by IHC.
In the recent World Health Organization (WHO) Classification of Tumors of Hematopoietic and Lymphoid Tissues 2017 revised edition a new entity, inflammatory pseudo-tumor-like follicular/fibroblastic dendritic cell sarcoma has been added.This entity has shown an association with EbsteinBar virus.[10] They occur in young to middle-aged adults with a female predilection.[11] Liver or spleen is the common organ involved with rare involvement of the gastrointestinal tract as a polypoidal lesion. Immunohistologically, they are similar to conventional FDCS with few areas resembling Reed–Sternberg cells and others showing marked eosinophilic infiltrate or epithelioid granulomas masking the tumor cell population. [12,13] Cases, which are negative for dendritic cell markers, express smooth muscle actin (SMA), denoting a fibroblastic reticular cell differentiation, hence the name fibroblastic dendritic cell sarcoma.
FDCs are tumors with an intermediate malignant potential and treated by complete surgical excision with or without adjuvant radiotherapy or chemotherapy. However, tumors of large size ≥6 cm, having coagulative necrosis,≥5 mitoses per 10 high-power fields (HPF) and significant atypia are associated with bad prognosis.[8],[14]
Diagnosing ENFDCS can be very challenging and easily be missed unless we keep a high index of suspicion. Therefore, any tumor with an ovoid to spindled cell histology having whorling architecture, ENFDCS should be kept as a differential irrespective of the location.
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Conflicts of interest
There are no conflicts of interest.
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Correspondence Address:
Anuj Khurana
98 SFS Flats, Phase 4 Ashok Vihar, Delhi - 110 052
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/IJPM.IJPM_316_20
[Figure 1], [Figure 2], [Figure 3] |
