His haemoglobin level was 7g%, though HPLC was reported as a normal haemoglobin variant. On clinical examination, a hard, non-tender lymph node was palpable in the left lower neck region. The lymph node biopsy was done, which showed partial subcapsular region effacement by small round blue cells [fig.1 A-D]. Those small, round blue tumour cells were strongly positive for synaptophysin and chromogranin and negative for CD45. Thus, the IHC profile proved the metastasis of neuroblastoma in the cervical lymph node in that child. The patient was advised to undergo urgent computed tomography (CT) of the whole abdomen, and a retroperitoneal mass was detected on the left side of the abdomen, superior to the kidney. The patient was subsequently planned for midline laparotomy. The resected tumour showed histopathological features of neuroblastoma primarily located in the right retroperitoneal region, as corroborated by IHC.

Another 15-year-old male patient presented with an abdominal lump in the left iliac fossa for the last two months associated with burning micturition. A CT scan of the abdomen showed a retroperitoneal SOL posterior to the urinary bladder. The patient had undergone an exploratory laparotomy. The HPE showed the presence of a small round cell tumour with pseudo-rosette formation [fig.2A]. The neoplastic cells were strongly positive for Synaptophysin and Chromogranin A. Thus, consistent with neuroblastoma.

Clear Cell Renal cell carcinoma: 3 cases

In our case series, we have encountered one unique case of RCC among three cases that presented primarily as a metastatic swelling in the left arm of a 50-year-old male patient. It was a painless, soft tissue nodule for the last 3months. Initially, FNAC was performed to rule out soft tissue lesions, but cytomorphology revealed tumour cells in clusters and aggregates with abundant, pale to vacuolated cytoplasm, indistinct cell borders, round, haphazard nuclei, and variable, prominent nucleoli, which raised suspicion [Fig. 3A]. The background shows vascular stromal components and necrohaemo-rrhagic areas. The patient was advised to undergo radiological imaging of the lower abdomen in search of the primary lesion. The excisional biopsy of that nodule showed compact nests and sheets of tumour cells with clear cytoplasm and distinct membranes, surrounding a network of arborising small, thin-walled vessels [Fig 3B].

the other one had a history of epigastric and right upper quadrant pain, nausea and vomiting since 2months. The CT scan revealed a defined, solid-cystic mass on the pancreatic head in both cases. [Fig.6A]. USG guided FNAC was performed in both cases, which showed cellular smears having loose cohesive clusters of tumour cells in delicate papillary fronds. Individual cells are uniform with a moderate amount of cytoplasm, perinuclear clear vacuolation, and round to oval nuclei with granular chromatin [Fig.6B]. An exploratory laparotomy was performed in both cases. Grossly, they were well-defined encapsulated masses. On HPE, the tumour was heterogeneous, comprising solid and pseudo-papillary areas. The tumour cells have round to elongated, uniform nuclei and characteristic longitudinal grooves. Areas of hyalinization. Degeneration and cystic changes were present. IHC picked the diagnosis of solid pseudopapillary neoplasm of pancreas(SPPN-P) as the tumour cells are Vimentin Positive and have aberrant nuclear Beta-catenin expression.[Fig.6C-E]

Paraganglioma: 1 case

A 59-year-old man, a known hypertensive, presented with pain in the left lumbar region. CT imaging showed a spherical lesion with rim enhancement close to the pancreatic tail. USG guided FNAC showed a cellular bloody smear, comprising poorly cohesive clusters of tumour cells having abundant, pale cytoplasm with indistinct cell borders forming a web-like background with fine red granulation in some of the cells. There is marked anisokaryosis with speckled chromatin and intranuclear pseudo-inclusions. The patient was planned for surgery and a biopsy. HPE shows ribbons, nests of round to oval polygonal cells separated by fibrovascular stroma (zellballen) pattern and often forming a pseudo-rosette. [Fig.7A] |he tumour cells are strongly positive for S100, GATA3 and chromogranin [Fig.7B, C] and negative for CD99, CD117.

Multilocular Cystic Renal Neoplasm of Low Malignant Potential (MCRNLMP): 1 case

A 45-year-old male patient presented with left flank pain and hypertension. CT scan showed an ill-defined diffuse mass in the left kidney with heterogeneous post-contrast enhancement. Radical nephrectomy was performed. It was a tan yellow multiloculated cystic mass 10x8 x4 cm grossly involving the entire kidney and perinephric fat.

On CT scan, multiloculated grape-like cystic mass arising from head & body of pancreas extending inf-eriorly along transverse mesocolon was seen. Pancreatic-splenectomy with left hemicolectomy was done. HPE showed multiloculated mucin-filled cystic tumour having tall cuboidal mucinous epithelial lining with focal branching papillary projections [Fig. 9A]. Low-grade dysplasia noted. No ovarian-type stroma found. Tumour was positive for CK7 & MUC2 [Fig.9B] & negative for MUC1. Therefore, final diagnosis of intest. type IPMN was rendered. 

Fig. 4A: The sheets of tumour cells are uniformly sized small round cells, slightly larger than small lymphocytes. Stippled chromatin with inconspicuous nucleoli, indistinct cytoplasmic membrane and clear to eosinophilic scanty cytoplasm noted on HPE (20X H&E stain) 4B: The small round cells contain a significant amount of cytoplasmic PAS-positive material 4C: CD99 was found to have strong and diffuse membranous expression in tumour cells-diagnostic of EWS.

6B: FNAC smear revealed loose cohesive clusters of bland uniform tumour cells. These cells have round to oval nuclei with a groove and finely granular chromatin, a moderate amount of cytoplasm, and perinuclear clear vacuolation suggestive of SPPN-P (Leishman stain,40X)

Fig. 7A: Distinct clusters and nests comprising epithelioid population of round to oval tumour cells separated by thin fibrovascular septa found in Paraganglioma of Retroperitoneal region (20X H&E stain) 7 7 7 7 7B: Paraganglioma cells are strongly nuclear reactive for GATA3. Fig. 7C: Diffuse cytoplasmic positive staining of Chromogranin - present in Paraganglioma cells.

8B: The nuclei of clear cells of MCRNLMP are positive for PAX8. 8C: The membranous expression of CD10 in the tumour cells confirms renal origin.

Fig. 9A: Pancreatic cystic mass lined by tall cuboidal epithelium with basally located nuclei without significant pleomorphism- HPE of intestinal type IPMN (40X H&E stain). 9B: The lining epithelium is MUC2+

Discussion

In our case series, the age range was 7 years to 50 years. We could find many rare tumours in the retroperitoneum, comprising malignant (50%), tumour of low malignant potential (40%) and benign tumours (10%) over a period of 2 years. Most of the primary retroperitoneal tumours are reported as malignant, similar to findings in previous case studies and series. The retroperitoneum is a quite large space, though its contents are heterogeneous, but kidney tumours were the most common, accounting for these case series.

AlRashed R and Wu, SY et al. have case reports of extraskeletal Ewing’s sarcoma in retroperitoneal location. [10], [11] and got a definitive diagnosis on tissue biopsy. EWSR1 rearrangement was first identified in Ewing's sarcoma, but these translocations were also found in other soft tissue tumours like Myxoid liposarcoma [12], Extraskeletal myxoid chondrosarcoma [13] and Clear cell sarcoma [14] in small percentages. In this case, we found nests, sheets of small, round cells separated by a thick fibrous band. The small cells have round nuclei, stippled chromatin and very scanty cytoplasm. So, the histomorphology along with relevant immunohistochemical markers, i.e CD 99, FLI-1, are needed for retroperitoneal EWS diagnosis.

SS is very uncommon in the retroperitoneal region. It can grow larger in this RP region and remains asymptomatic unless it compresses the adjacent organ. Histologically, the tumour was monophasic in this case series and was challenging to diagnose. The tumour cells were positive for S100, BCL-2, and TLE-1, which enabled us to reach the diagnosis of poorly differentiated SS. Sarra Ben Rejeb et.al and Ansari Djafari A et.al could report the case of huge monophasic RPSS separately with molecular diagnosis. [15], [16] by the former author. We have no scope for molecular analysis for SS in our institution. We could find two cases of SPPN-P in female patients. SPPT is a rare tumour of the pancreas, accounting for only 1-2% of all pancreatic neoplasms, with a preponderance in young women. [17] In our case series, we found similar cases in a very young girl of 14 years and a woman of 27 years. Most of the data on SPPT was a case report or a small case series. WHO has classified it as a low-grade malignant neoplasm in 2010 [18], but few cases are reported in the literature with malignant metastatic potential [19] with high serum CA125 and tumour size >5cm. The pathogenesis is still unclear, but it can arise from pluripotent stem cells in the retroperitoneum and could be due to mutations in the β-catenin gene. In this case series, both tumours were < 5cm in maximum diameter, and no metastasis was found. Retroperitoneal Paragangliomas are very rare tumours, generally arising from the chromaffin cells of the sympathetic chain and the adrenal gland. They can arise from an extra adrenal site in 15% of the population and remain asymptomatic in 10 to 30 % cases [20].

The majority of reported cases of MCRNLMP are of low pathologic stage, but extension to perinephric fat is a unique and unusual presentation in our case series, like previous reporting by Murshed KA et.al [24].

IPMN is quite common in the old age group > 65 years, with a common symptom of upper abdominal pain. It can arise from - main duct, branched duct, multicentric and of three types on histomorphology- Gastric, Intestinal and Pancreaticobiliary. Malignancy predisposition [25] is found more with main duct IPMN (60%) than mixed, followed by branched (12-30%). In our series, it was a cystic mass filled with mucin involving the head and body of the pancreas. Low-grade dysplasia was found on microscopy. Histomorphology was of intestinal type IPMN, ascertained as tumour cells were positive for MUC-2and negative for MUC-1. This case was unique as a case report of branched duct-intestinal type IPMN is rare.

Limitation: The compiled and studied retroperitoneal cases in this period were small in sample size, as other cases couldn't be presented here due to incompleteness of required data and untraceable patients. The molecular and cytogenetic studies are not available in our institute.

Conclusions

The exact diagnosis of RPT is troublesome and quite challenging. Most of the RPTs are malignant, but as the space is large enough to allow the tumour growth silently, the clinical symptoms develop later. Guided FNAC often helps for initial diagnosis, but ultimately, HPE on biopsy is still considered the gold standard for diagnosis and aid for other ancillary investigations like IHC and molecular studies.

Funding: No financial support taken

Conflict of interest: None declared

Ethical approval: Not required in our institution for case series

References